commit 1d1f898df6586c5ea9aeaf349f13089c6fa37903 upstream.
The rcu_gp_kthread_wake() function is invoked when it might be necessary
to wake the RCU grace-period kthread. Because self-wakeups are normally
a useless waste of CPU cycles, if rcu_gp_kthread_wake() is invoked from
this kthread, it naturally refuses to do the wakeup.
Unfortunately, natural though it might be, this heuristic fails when
rcu_gp_kthread_wake() is invoked from an interrupt or softirq handler
that interrupted the grace-period kthread just after the final check of
the wait-event condition but just before the schedule() call. In this
case, a wakeup is required, even though the call to rcu_gp_kthread_wake()
is within the RCU grace-period kthread's context. Failing to provide
this wakeup can result in grace periods failing to start, which in turn
results in out-of-memory conditions.
This race window is quite narrow, but it actually did happen during real
testing. It would of course need to be fixed even if it was strictly
theoretical in nature.
This patch does not Cc stable because it does not apply cleanly to
earlier kernel versions.
Fixes: 48a7639ce80c ("rcu: Make callers awaken grace-period kthread")
Reported-by: "He, Bo" <bo.he@intel.com>
Co-developed-by: "Zhang, Jun" <jun.zhang@intel.com>
Co-developed-by: "He, Bo" <bo.he@intel.com>
Co-developed-by: "xiao, jin" <jin.xiao@intel.com>
Co-developed-by: Bai, Jie A <jie.a.bai@intel.com>
Signed-off: "Zhang, Jun" <jun.zhang@intel.com>
Signed-off: "He, Bo" <bo.he@intel.com>
Signed-off: "xiao, jin" <jin.xiao@intel.com>
Signed-off: Bai, Jie A <jie.a.bai@intel.com>
Signed-off-by: "Zhang, Jun" <jun.zhang@intel.com>
[ paulmck: Switch from !in_softirq() to "!in_interrupt() &&
!in_serving_softirq() to avoid redundant wakeups and to also handle the
interrupt-handler scenario as well as the softirq-handler scenario that
actually occurred in testing. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Link: https://lkml.kernel.org/r/CD6925E8781EFD4D8E11882D20FC406D52A11F61@SHSMSX104.ccr.corp.intel.com
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
[ Upstream commit f6e2aa91a46d2bc79fce9b93a988dbe7655c90c0 ]
Recently syzbot in conjunction with KMSAN reported that
ptrace_peek_siginfo can copy an uninitialized siginfo to userspace.
Inspecting ptrace_peek_siginfo confirms this.
The problem is that off when initialized from args.off can be
initialized to a negaive value. At which point the "if (off >= 0)"
test to see if off became negative fails because off started off
negative.
Prevent the core problem by adding a variable found that is only true
if a siginfo is found and copied to a temporary in preparation for
being copied to userspace.
Prevent args.off from being truncated when being assigned to off by
testing that off is <= the maximum possible value of off. Convert off
to an unsigned long so that we should not have to truncate args.off,
we have well defined overflow behavior so if we add another check we
won't risk fighting undefined compiler behavior, and so that we have a
type whose maximum value is easy to test for.
Cc: Andrei Vagin <avagin@gmail.com>
Cc: stable@vger.kernel.org
Reported-by: syzbot+0d602a1b0d8c95bdf299@syzkaller.appspotmail.com
Fixes: 84c751bd4a ("ptrace: add ability to retrieve signals without removing from a queue (v4)")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 80e3d87b2c5582db0ab5e39610ce3707d97ba409 upstream.
This patch adds checks that prevens futile attempts to move rt tasks
to a CPU with active tasks of equal or higher priority.
This reduces run queue lock contention and improves the performance of
a well known OLTP benchmark by 0.7%.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>
Cc: Suruchi Kadu <suruchi.a.kadu@intel.com>
Cc: Doug Nelson<doug.nelson@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1421430374.2399.27.camel@schen9-desk2.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
For better use of CPU idle time, allow the scheduler to select the CPU
on which the SRCU grace period work would be scheduled. This improves
idle residency time and conserves power.
This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Shaibal Dutta <shaibal.dutta@broadcom.com>
[zoran.markovic@linaro.org: Rebased to latest kernel version. Added commit
message. Fixed code alignment.]
Signed-off-by: Zoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
For better use of CPU idle time, allow the scheduler to select the CPU
on which the CMOS clock sync work would be scheduled. This improves
idle residency time and conserver power.
This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.
Signed-off-by: Shaibal Dutta <shaibal.dutta@broadcom.com>
[zoran.markovic@linaro.org: Added commit message. Aligned code.]
Signed-off-by: Zoran Markovic <zoran.markovic@linaro.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1391195904-12497-1-git-send-email-zoran.markovic@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
In 76854c7e8f ("sched: Use
rt.nr_cpus_allowed to recover select_task_rq() cycles") an
optimization was added to select_task_rq_rt() that immediately
returns when p->nr_cpus_allowed == 1 at the beginning of the
function.
This makes the latter p->nr_cpus_allowed > 1 check redundant,
which can now be removed.
Signed-off-by: Shawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <mgalbraith@suse.de>
Cc: tomk@rgmadvisors.com
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1380914693-24634-1-git-send-email-shawn.bohrer@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch adds system wide workqueues aligned towards power saving. This is
done by allocating them with WQ_UNBOUND flag if 'wq_power_efficient' is set to
'true'.
tj: updated comments a bit.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Workqueues can be performance or power-oriented. Currently, most workqueues are
bound to the CPU they were created on. This gives good performance (due to cache
effects) at the cost of potentially waking up otherwise idle cores (Idle from
scheduler's perspective. Which may or may not be physically idle) just to
process some work. To save power, we can allow the work to be rescheduled on a
core that is already awake.
Workqueues created with the WQ_UNBOUND flag will allow some power savings.
However, we don't change the default behaviour of the system. To enable
power-saving behaviour, a new config option CONFIG_WQ_POWER_EFFICIENT needs to
be turned on. This option can also be overridden by the
workqueue.power_efficient boot parameter.
tj: Updated config description and comments. Renamed
CONFIG_WQ_POWER_EFFICIENT to CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
The kernel passes any args it doesn't need through to init, except it
assumes anything containing '.' belongs to the kernel (for a module).
This change means all users can clearly distinguish which arguments
are for init.
For example, the kernel uses debug ("dee-bug") to mean log everything to
the console, where systemd uses the debug from the Scandinavian "day-boog"
meaning "fail to boot". If a future versions uses argv[] instead of
reading /proc/cmdline, this confusion will be avoided.
eg: test 'FOO="this is --foo"' -- 'systemd.debug="true true true"'
Gives:
argv[0] = '/debug-init'
argv[1] = 'test'
argv[2] = 'systemd.debug=true true true'
envp[0] = 'HOME=/'
envp[1] = 'TERM=linux'
envp[2] = 'FOO=this is --foo'
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Although parameters are supposed to be part of the kernel API, experimental
parameters are often removed. In addition, downgrading a kernel might cause
previously-working modules to fail to load.
On balance, it's probably better to warn, and load the module anyway.
This may let through a typo, but at least the logs will show it.
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
commit d6097c9e4454adf1f8f2c9547c2fa6060d55d952 upstream.
Unless the very next line is schedule(), or implies it, one must not use
preempt_enable_no_resched(). It can cause a preemption to go missing and
thereby cause arbitrary delays, breaking the PREEMPT=y invariant.
Link: http://lkml.kernel.org/r/20190423200318.GY14281@hirez.programming.kicks-ass.net
Cc: Waiman Long <longman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: the arch/x86 maintainers <x86@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: huang ying <huang.ying.caritas@gmail.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: stable@vger.kernel.org
Fixes: 2c2d7329d8 ("tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Serge Hallyn <serge.hallyn@ubuntu.com> writes:
> Hi Oleg,
>
> commit 40a0d32d1eaffe6aac7324ca92604b6b3977eb0e :
> "fork: unify and tighten up CLONE_NEWUSER/CLONE_NEWPID checks"
> breaks lxc-attach in 3.12. That code forks a child which does
> setns() and then does a clone(CLONE_PARENT). That way the
> grandchild can be in the right namespaces (which the child was
> not) and be a child of the original task, which is the monitor.
>
> lxc-attach in 3.11 was working fine with no side effects that I
> could see. Is there a real danger in allowing CLONE_PARENT
> when current->nsproxy->pidns_for_children is not our pidns,
> or was this done out of an "over-abundance of caution"? Can we
> safely revert that new extra check?
The two fundamental things I know we can not allow are:
- A shared signal queue aka CLONE_THREAD. Because we compute the pid
and uid of the signal when we place it in the queue.
- Changing the pid and by extention pid_namespace of an existing
process.
From a parents perspective there is nothing special about the pid
namespace, to deny CLONE_PARENT, because the parent simply won't know or
care.
From the childs perspective all that is special really are shared signal
queues.
User mode threading with CLONE_PARENT|CLONE_VM|CLONE_SIGHAND and tasks
in different pid namespaces is almost certainly going to break because
it is complicated. But shared signal handlers can look at per thread
information to know which pid namespace a process is in, so I don't know
of any reason not to support CLONE_PARENT|CLONE_VM|CLONE_SIGHAND threads
at the kernel level. It would be absolutely stupid to implement but
that is a different thing.
So hmm.
Because it can do no harm, and because it is a regression let's remove
the CLONE_PARENT check and send it stable.
Cc: stable@vger.kernel.org
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
do_fork() denies CLONE_THREAD | CLONE_PARENT if NEWUSER | NEWPID.
Then later copy_process() denies CLONE_SIGHAND if the new process will
be in a different pid namespace (task_active_pid_ns() doesn't match
current->nsproxy->pid_ns).
This looks confusing and inconsistent. CLONE_NEWPID is very similar to
the case when ->pid_ns was already unshared, we want the same
restrictions so copy_process() should also nack CLONE_PARENT.
And it would be better to deny CLONE_NEWUSER && CLONE_SIGHAND as well
just for consistency.
Kill the "CLONE_NEWUSER | CLONE_NEWPID" check in do_fork() and change
copy_process() to do the same check along with ->pid_ns check we already
have.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Colin Walters <walters@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 8382fcac1b ("pidns: Outlaw thread creation after
unshare(CLONE_NEWPID)") nacks CLONE_NEWPID if the forking process
unshared pid_ns. This is correct but unnecessary, copy_pid_ns() does
the same check.
Remove the CLONE_NEWPID check to cleanup the code and prepare for the
next change.
Test-case:
static int child(void *arg)
{
return 0;
}
static char stack[16 * 1024];
int main(void)
{
pid_t pid;
assert(unshare(CLONE_NEWUSER | CLONE_NEWPID) == 0);
pid = clone(child, stack + sizeof(stack) / 2,
CLONE_NEWPID | SIGCHLD, NULL);
assert(pid < 0 && errno == EINVAL);
return 0;
}
clone(CLONE_NEWPID) correctly fails with or without this change.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Colin Walters <walters@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
nsproxy.pid_ns is *not* the task's pid namespace. The name should clarify
that.
This makes it more obvious that setns on a pid namespace is weird --
it won't change the pid namespace shown in procfs.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
A zombie task obviously can't fork(), remove the unnecessary
initialization of child->exit_state. It is zero anyway after
dup_task_struct().
Note: copy_process() is huge and it has a lot of chaotic
initializations, probably it makes sense to move them into the
new helper called by dup_task_struct().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131113143612.GA10540@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
copy_process() adds the new child to thread_group/init_task.tasks list and
then does attach_pid(child, PIDTYPE_PID). This means that the lockless
next_thread() or next_task() can see this thread with the wrong pid. Say,
"ls /proc/pid/task" can list the same inode twice.
We could move attach_pid(child, PIDTYPE_PID) up, but in this case
find_task_by_vpid() can find the new thread before it was fully
initialized.
And this is already true for PIDTYPE_PGID/PIDTYPE_SID, With this patch
copy_process() initializes child->pids[*].pid first, then calls
attach_pid() to insert the task into the pid->tasks list.
attach_pid() no longer need the "struct pid*" argument, it is always
called after pid_link->pid was already set.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Sergey Dyasly <dserrg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
"case 0" in free_pid() assumes that disable_pid_allocation() should
clear PIDNS_HASH_ADDING before the last pid goes away.
However this doesn't happen if the first fork() fails to create the
child reaper which should call disable_pid_allocation().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 7b55851367136b1efd84d98fea81ba57a98304cf upstream.
This changes the fork(2) syscall to record the process start_time after
initializing the basic task structure but still before making the new
process visible to user-space.
Technically, we could record the start_time anytime during fork(2). But
this might lead to scenarios where a start_time is recorded long before
a process becomes visible to user-space. For instance, with
userfaultfd(2) and TLS, user-space can delay the execution of fork(2)
for an indefinite amount of time (and will, if this causes network
access, or similar).
By recording the start_time late, it much closer reflects the point in
time where the process becomes live and can be observed by other
processes.
Lastly, this makes it much harder for user-space to predict and control
the start_time they get assigned. Previously, user-space could fork a
process and stall it in copy_thread_tls() before its pid is allocated,
but after its start_time is recorded. This can be misused to later-on
cycle through PIDs and resume the stalled fork(2) yielding a process
that has the same pid and start_time as a process that existed before.
This can be used to circumvent security systems that identify processes
by their pid+start_time combination.
Even though user-space was always aware that start_time recording is
flaky (but several projects are known to still rely on start_time-based
identification), changing the start_time to be recorded late will help
mitigate existing attacks and make it much harder for user-space to
control the start_time a process gets assigned.
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.16: start_time initialisation code is different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 3fd37226216620c1a468afa999739d5016fbc349 upstream.
Imagine we have a pid namespace and a task from its parent's pid_ns,
which made setns() to the pid namespace. The task is doing fork(),
while the pid namespace's child reaper is dying. We have the race
between them:
Task from parent pid_ns Child reaper
copy_process() ..
alloc_pid() ..
.. zap_pid_ns_processes()
.. disable_pid_allocation()
.. read_lock(&tasklist_lock)
.. iterate over pids in pid_ns
.. kill tasks linked to pids
.. read_unlock(&tasklist_lock)
write_lock_irq(&tasklist_lock); ..
attach_pid(p, PIDTYPE_PID); ..
.. ..
So, just created task p won't receive SIGKILL signal,
and the pid namespace will be in contradictory state.
Only manual kill will help there, but does the userspace
care about this? I suppose, the most users just inject
a task into a pid namespace and wait a SIGCHLD from it.
The patch fixes the problem. It simply checks for
(pid_ns->nr_hashed & PIDNS_HASH_ADDING) in copy_process().
We do it under the tasklist_lock, and can't skip
PIDNS_HASH_ADDING as noted by Oleg:
"zap_pid_ns_processes() does disable_pid_allocation()
and then takes tasklist_lock to kill the whole namespace.
Given that copy_process() checks PIDNS_HASH_ADDING
under write_lock(tasklist) they can't race;
if copy_process() takes this lock first, the new child will
be killed, otherwise copy_process() can't miss
the change in ->nr_hashed."
If allocation is disabled, we just return -ENOMEM
like it's made for such cases in alloc_pid().
v2: Do not move disable_pid_allocation(), do not
introduce a new variable in copy_process() and simplify
the patch as suggested by Oleg Nesterov.
Account the problem with double irq enabling
found by Eric W. Biederman.
Fixes: c876ad7682 ("pidns: Stop pid allocation when init dies")
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Oleg Nesterov <oleg@redhat.com>
CC: Mike Rapoport <rppt@linux.vnet.ibm.com>
CC: Michal Hocko <mhocko@suse.com>
CC: Andy Lutomirski <luto@kernel.org>
CC: "Eric W. Biederman" <ebiederm@xmission.com>
CC: Andrei Vagin <avagin@openvz.org>
CC: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Serge Hallyn <serge@hallyn.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
[bwh: Backported to 3.16: the proper cleanup label is bad_fork_free_pid, not
bad_fork_cancel_cgroup]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
dup_mm() is used only in kernel/fork.c
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix errors reported by checkpatch.pl. One error is parentheses, the other
is a whitespace issue.
Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When a task is attempting to violate the RLIMIT_NPROC limit we have a
check to see if the task is sufficiently priviledged. The check first
looks at CAP_SYS_ADMIN, then CAP_SYS_RESOURCE, then if the task is uid=0.
A result is that tasks which are allowed by the uid=0 check are first
checked against the security subsystem. This results in the security
subsystem auditting a denial for sys_admin and sys_resource and then the
task passing the uid=0 check.
This patch rearranges the code to first check uid=0, since if we pass that
we shouldn't hit the security system at all. We then check sys_resource,
since it is the smallest capability which will solve the problem. Lastly
we check the fallback everything cap_sysadmin. We don't want to give this
capability many places since it is so powerful.
This will eliminate many of the false positive/needless denial messages we
get when a root task tries to violate the nproc limit. (note that
kthreads count against root, so on a sufficiently large machine we can
actually get past the default limits before any userspace tasks are
launched.)
Signed-off-by: Eric Paris <eparis@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
copy_process() does a lot of "chaotic" initializations and checks
CLONE_THREAD twice before it takes tasklist. In particular it sets
"p->group_leader = p" and then changes it again under tasklist if
!thread_group_leader(p).
This looks a bit confusing, lets create a single "if (CLONE_THREAD)" block
which initializes ->exit_signal, ->group_leader, and ->tgid.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Sergey Dyasly <dserrg@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To increase compiler portability there is <linux/compiler.h> which
provides convenience macros for various gcc constructs. Eg: __weak for
__attribute__((weak)). I've replaced all instances of gcc attributes
with the right macro in the kernel subsystem.
Signed-off-by: Gideon Israel Dsouza <gidisrael@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that allow_signal() is really trivial we can unify it with
disallow_signal(). Add the new helper, kernel_sigaction(), and
reimplement allow_signal/disallow_signal as a trivial wrappers.
This saves one EXPORT_SYMBOL() and the new helper can have more users.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
disallow_signal() simply sets SIG_IGN, this is not enough and
recalc_sigpending() is simply pointless because in can never change the
state of TIF_SIGPENDING.
If we ignore a signal, we also need to do flush_sigqueue_mask() for the
case when this signal is pending, this way recalc_sigpending() can
actually clear TIF_SIGPENDING and we do not "leak" the allocated
siginfo's.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
allow_signal() does sigdelset(current->blocked) due to historic reason,
previously it could be called by a daemonize()'ed kthread, and
daemonize() played with current->blocked.
Now that daemonize() has gone away we can remove sigdelset() and
recalc_sigpending(). If a user really wants to unblock a signal, it
must use sigprocmask() or set_current_block() explicitely.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I found the following pattern that leads in to interesting findings:
grep -r "ret.*|=.*__put_user" *
grep -r "ret.*|=.*__get_user" *
grep -r "ret.*|=.*__copy" *
The __put_user() calls in compat_ioctl.c, ptrace compat, signal compat,
since those appear in compat code, we could probably expect the kernel
addresses not to be reachable in the lower 32-bit range, so I think they
might not be exploitable.
For the "__get_user" cases, I don't think those are exploitable: the worse
that can happen is that the kernel will copy kernel memory into in-kernel
buffers, and will fail immediately afterward.
The alpha csum_partial_copy_from_user() seems to be missing the
access_ok() check entirely. The fix is inspired from x86. This could
lead to information leak on alpha. I also noticed that many architectures
map csum_partial_copy_from_user() to csum_partial_copy_generic(), but I
wonder if the latter is performing the access checks on every
architectures.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 3597dfe01d12f570bc739da67f857fd222a3ea66 upstream.
Instead of playing whack-a-mole and changing SEND_SIG_PRIV to
SEND_SIG_FORCED throughout the kernel to ensure a pid namespace init
gets signals sent by the kernel, stop allowing a pid namespace init to
ignore SIGKILL or SIGSTOP sent by the kernel. A pid namespace init is
only supposed to be able to ignore signals sent from itself and
children with SIG_DFL.
Fixes: 921cf9f630 ("signals: protect cinit from unblocked SIG_DFL signals")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit cf43a757fd49442bc38f76088b70c2299eed2c2f upstream.
In the middle of do_exit() there is there is a call
"ptrace_event(PTRACE_EVENT_EXIT, code);" That call places the process
in TACKED_TRACED aka "(TASK_WAKEKILL | __TASK_TRACED)" and waits for
for the debugger to release the task or SIGKILL to be delivered.
Skipping past dequeue_signal when we know a fatal signal has already
been delivered resulted in SIGKILL remaining pending and
TIF_SIGPENDING remaining set. This in turn caused the
scheduler to not sleep in PTACE_EVENT_EXIT as it figured
a fatal signal was pending. This also caused ptrace_freeze_traced
in ptrace_check_attach to fail because it left a per thread
SIGKILL pending which is what fatal_signal_pending tests for.
This difference in signal state caused strace to report
strace: Exit of unknown pid NNNNN ignored
Therefore update the signal handling state like dequeue_signal
would when removing a per thread SIGKILL, by removing SIGKILL
from the per thread signal mask and clearing TIF_SIGPENDING.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Ivan Delalande <colona@arista.com>
Fixes: 35634ffa1751 ("signal: Always notice exiting tasks")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 528871b456026e6127d95b1b2bd8e3a003dc1614 upstream.
The following commit:
9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes")
results in perf recording failures with larger mmap areas:
root@skl:/tmp# perf record -g -a
failed to mmap with 12 (Cannot allocate memory)
The root cause is that the following condition is buggy:
if (order_base_2(size) >= MAX_ORDER)
goto fail;
The problem is that @size is in bytes and MAX_ORDER is in pages,
so the right test is:
if (order_base_2(size) >= PAGE_SHIFT+MAX_ORDER)
goto fail;
Fix it.
Reported-by: "Jin, Yao" <yao.jin@linux.intel.com>
Bisected-by: Borislav Petkov <bp@alien8.de>
Analyzed-by: Peter Zijlstra <peterz@infradead.org>
Cc: Julien Thierry <julien.thierry@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Fixes: 9dff0aa95a32 ("perf/core: Don't WARN() for impossible ring-buffer sizes")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 7146db3317c67b517258cb5e1b08af387da0618b upstream.
Recently syzkaller was able to create unkillablle processes by
creating a timer that is delivered as a thread local signal on SIGHUP,
and receiving SIGHUP SA_NODEFERER. Ultimately causing a loop failing
to deliver SIGHUP but always trying.
When the stack overflows delivery of SIGHUP fails and force_sigsegv is
called. Unfortunately because SIGSEGV is numerically higher than
SIGHUP next_signal tries again to deliver a SIGHUP.
From a quality of implementation standpoint attempting to deliver the
timer SIGHUP signal is wrong. We should attempt to deliver the
synchronous SIGSEGV signal we just forced.
We can make that happening in a fairly straight forward manner by
instead of just looking at the signal number we also look at the
si_code. In particular for exceptions (aka synchronous signals) the
si_code is always greater than 0.
That still has the potential to pick up a number of asynchronous
signals as in a few cases the same si_codes that are used
for synchronous signals are also used for asynchronous signals,
and SI_KERNEL is also included in the list of possible si_codes.
Still the heuristic is much better and timer signals are definitely
excluded. Which is enough to prevent all known ways for someone
sending a process signals fast enough to cause unexpected and
arguably incorrect behavior.
Fixes: a27341cd5f ("Prioritize synchronous signals over 'normal' signals")
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
[bwh: Backported to 3.16: s/kernel_siginfo_t/siginfo_t/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 35634ffa1751b6efd8cf75010b509dcb0263e29b upstream.
Recently syzkaller was able to create unkillablle processes by
creating a timer that is delivered as a thread local signal on SIGHUP,
and receiving SIGHUP SA_NODEFERER. Ultimately causing a loop
failing to deliver SIGHUP but always trying.
Upon examination it turns out part of the problem is actually most of
the solution. Since 2.5 signal delivery has found all fatal signals,
marked the signal group for death, and queued SIGKILL in every threads
thread queue relying on signal->group_exit_code to preserve the
information of which was the actual fatal signal.
The conversion of all fatal signals to SIGKILL results in the
synchronous signal heuristic in next_signal kicking in and preferring
SIGHUP to SIGKILL. Which is especially problematic as all
fatal signals have already been transformed into SIGKILL.
Instead of dequeueing signals and depending upon SIGKILL to
be the first signal dequeued, first test if the signal group
has already been marked for death. This guarantees that
nothing in the signal queue can prevent a process that needs
to exit from exiting.
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Ref: ebf5ebe31d2c ("[PATCH] signal-fixes-2.5.59-A4")
History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 828b1f65d23cf8a68795739f6dd08fc8abd9ee64 upstream.
Now we can turn get_signal() to the main function.
Signed-off-by: Richard Weinberger <richard@nod.at>
[bwh: Backported to 3.16 as dependency of commit 35634ffa1751
"signal: Always notice exiting tasks"]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 10b1c7ac8bfed429cf3dcb0225482c8dc1485d8e upstream.
- Pass a ksignal struct to it
- Remove unused regs parameter
- Make it private as it's nowhere outside of kernel/signal.c is used
Signed-off-by: Richard Weinberger <richard@nod.at>
[bwh: Backported to 3.16 as dependency of commit 35634ffa1751
"signal: Always notice exiting tasks"]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This patch fix spelling typo in Documentation/DocBook.
It is because .html and .xml files are generated by make htmldocs,
I have to fix a typo within the source files.
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
commit df5601f9c3d831b4c478b004a1ed90a18643adbe upstream.
These parameters are nowhere used, so we can remove them.
Signed-off-by: Richard Weinberger <richard@nod.at>
[bwh: Backported to 3.16 as dependency of commit 35634ffa1751
"signal: Always notice exiting tasks"]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 9dff0aa95a324e262ffb03f425d00e4751f3294e upstream.
The perf tool uses /proc/sys/kernel/perf_event_mlock_kb to determine how
large its ringbuffer mmap should be. This can be configured to arbitrary
values, which can be larger than the maximum possible allocation from
kmalloc.
When this is configured to a suitably large value (e.g. thanks to the
perf fuzzer), attempting to use perf record triggers a WARN_ON_ONCE() in
__alloc_pages_nodemask():
WARNING: CPU: 2 PID: 5666 at mm/page_alloc.c:4511 __alloc_pages_nodemask+0x3f8/0xbc8
Let's avoid this by checking that the requested allocation is possible
before calling kzalloc.
Reported-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190110142745.25495-1-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
commit 9002b21465fa4d829edfc94a5a441005cffaa972 upstream.
Commit 32a5ad9c2285 ("sysctl: handle overflow for file-max") hooked up
min/max values for the file-max sysctl parameter via the .extra1 and
.extra2 fields in the corresponding struct ctl_table entry.
Unfortunately, the minimum value points at the global 'zero' variable,
which is an int. This results in a KASAN splat when accessed as a long
by proc_doulongvec_minmax on 64-bit architectures:
| BUG: KASAN: global-out-of-bounds in __do_proc_doulongvec_minmax+0x5d8/0x6a0
| Read of size 8 at addr ffff2000133d1c20 by task systemd/1
|
| CPU: 0 PID: 1 Comm: systemd Not tainted 5.1.0-rc3-00012-g40b114779944 #2
| Hardware name: linux,dummy-virt (DT)
| Call trace:
| dump_backtrace+0x0/0x228
| show_stack+0x14/0x20
| dump_stack+0xe8/0x124
| print_address_description+0x60/0x258
| kasan_report+0x140/0x1a0
| __asan_report_load8_noabort+0x18/0x20
| __do_proc_doulongvec_minmax+0x5d8/0x6a0
| proc_doulongvec_minmax+0x4c/0x78
| proc_sys_call_handler.isra.19+0x144/0x1d8
| proc_sys_write+0x34/0x58
| __vfs_write+0x54/0xe8
| vfs_write+0x124/0x3c0
| ksys_write+0xbc/0x168
| __arm64_sys_write+0x68/0x98
| el0_svc_common+0x100/0x258
| el0_svc_handler+0x48/0xc0
| el0_svc+0x8/0xc
|
| The buggy address belongs to the variable:
| zero+0x0/0x40
|
| Memory state around the buggy address:
| ffff2000133d1b00: 00 00 00 00 00 00 00 00 fa fa fa fa 04 fa fa fa
| ffff2000133d1b80: fa fa fa fa 04 fa fa fa fa fa fa fa 04 fa fa fa
| >ffff2000133d1c00: fa fa fa fa 04 fa fa fa fa fa fa fa 00 00 00 00
| ^
| ffff2000133d1c80: fa fa fa fa 00 fa fa fa fa fa fa fa 00 00 00 00
| ffff2000133d1d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Fix the splat by introducing a unsigned long 'zero_ul' and using that
instead.
Link: http://lkml.kernel.org/r/20190403153409.17307-1-will.deacon@arm.com
Fixes: 32a5ad9c2285 ("sysctl: handle overflow for file-max")
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Christian Brauner <christian@brauner.io>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 2e8e19226398db8265a8e675fcc0118b9e80c9e8 ]
With extremely short cfs_period_us setting on a parent task group with a large
number of children the for loop in sched_cfs_period_timer() can run until the
watchdog fires. There is no guarantee that the call to hrtimer_forward_now()
will ever return 0. The large number of children can make
do_sched_cfs_period_timer() take longer than the period.
NMI watchdog: Watchdog detected hard LOCKUP on cpu 24
RIP: 0010:tg_nop+0x0/0x10
<IRQ>
walk_tg_tree_from+0x29/0xb0
unthrottle_cfs_rq+0xe0/0x1a0
distribute_cfs_runtime+0xd3/0xf0
sched_cfs_period_timer+0xcb/0x160
? sched_cfs_slack_timer+0xd0/0xd0
__hrtimer_run_queues+0xfb/0x270
hrtimer_interrupt+0x122/0x270
smp_apic_timer_interrupt+0x6a/0x140
apic_timer_interrupt+0xf/0x20
</IRQ>
To prevent this we add protection to the loop that detects when the loop has run
too many times and scales the period and quota up, proportionally, so that the timer
can complete before then next period expires. This preserves the relative runtime
quota while preventing the hard lockup.
A warning is issued reporting this state and the new values.
Signed-off-by: Phil Auld <pauld@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Anton Blanchard <anton@ozlabs.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190319130005.25492-1-pauld@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 32a5ad9c22852e6bd9e74bdec5934ef9d1480bc5 ]
Currently, when writing
echo 18446744073709551616 > /proc/sys/fs/file-max
/proc/sys/fs/file-max will overflow and be set to 0. That quickly
crashes the system.
This commit sets the max and min value for file-max. The max value is
set to long int. Any higher value cannot currently be used as the
percpu counters are long ints and not unsigned integers.
Note that the file-max value is ultimately parsed via
__do_proc_doulongvec_minmax(). This function does not report error when
min or max are exceeded. Which means if a value largen that long int is
written userspace will not receive an error instead the old value will be
kept. There is an argument to be made that this should be changed and
__do_proc_doulongvec_minmax() should return an error when a dedicated min
or max value are exceeded. However this has the potential to break
userspace so let's defer this to an RFC patch.
Link: http://lkml.kernel.org/r/20190107222700.15954-3-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Waiman Long <longman@redhat.com>
[christian@brauner.io: v4]
Link: http://lkml.kernel.org/r/20190210203943.8227-3-christian@brauner.io
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 31b265b3baaf55f209229888b7ffea523ddab366 ]
As reported back in 2016-11 [1], the "ftdump" kdb command triggers a
BUG for "sleeping function called from invalid context".
kdb's "ftdump" command wants to call ring_buffer_read_prepare() in
atomic context. A very simple solution for this is to add allocation
flags to ring_buffer_read_prepare() so kdb can call it without
triggering the allocation error. This patch does that.
Note that in the original email thread about this, it was suggested
that perhaps the solution for kdb was to either preallocate the buffer
ahead of time or create our own iterator. I'm hoping that this
alternative of adding allocation flags to ring_buffer_read_prepare()
can be considered since it means I don't need to duplicate more of the
core trace code into "trace_kdb.c" (for either creating my own
iterator or re-preparing a ring allocator whose memory was already
allocated).
NOTE: another option for kdb is to actually figure out how to make it
reuse the existing ftrace_dump() function and totally eliminate the
duplication. This sounds very appealing and actually works (the "sr
z" command can be seen to properly dump the ftrace buffer). The
downside here is that ftrace_dump() fully consumes the trace buffer.
Unless that is changed I'd rather not use it because it means "ftdump
| grep xyz" won't be very useful to search the ftrace buffer since it
will throw away the whole trace on the first grep. A future patch to
dump only the last few lines of the buffer will also be hard to
implement.
[1] https://lkml.kernel.org/r/20161117191605.GA21459@google.com
Link: http://lkml.kernel.org/r/20190308193205.213659-1-dianders@chromium.org
Reported-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit bf959931ddb88c4e4366e96dd22e68fa0db9527c upstream.
The following program (simplified version of generated by syzkaller)
#include <pthread.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <stdio.h>
#include <signal.h>
void *thread_func(void *arg)
{
ptrace(PTRACE_TRACEME, 0,0,0);
return 0;
}
int main(void)
{
pthread_t thread;
if (fork())
return 0;
while (getppid() != 1)
;
pthread_create(&thread, NULL, thread_func, NULL);
pthread_join(thread, NULL);
return 0;
}
creates an unreapable zombie if /sbin/init doesn't use __WALL.
This is not a kernel bug, at least in a sense that everything works as
expected: debugger should reap a traced sub-thread before it can reap the
leader, but without __WALL/__WCLONE do_wait() ignores sub-threads.
Unfortunately, it seems that /sbin/init in most (all?) distributions
doesn't use it and we have to change the kernel to avoid the problem.
Note also that most init's use sys_waitid() which doesn't allow __WALL, so
the necessary user-space fix is not that trivial.
This patch just adds the "ptrace" check into eligible_child(). To some
degree this matches the "tsk->ptrace" in exit_notify(), ->exit_signal is
mostly ignored when the tracee reports to debugger. Or WSTOPPED, the
tracer doesn't need to set this flag to wait for the stopped tracee.
This obviously means the user-visible change: __WCLONE and __WALL no
longer have any meaning for debugger. And I can only hope that this won't
break something, but at least strace/gdb won't suffer.
We could make a more conservative change. Say, we can take __WCLONE into
account, or !thread_group_leader(). But it would be nice to not
complicate these historical/confusing checks.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: <syzkaller@googlegroups.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This reverts commit bf26c01849 ("Prepare to fix racy accesses on task
breakpoints").
The patch was fine but we can no longer race with SIGKILL after commit
9899d11f65 ("ptrace: ensure arch_ptrace/ptrace_request can never race
with SIGKILL"), the __TASK_TRACED tracee can't be woken up and
->ptrace_bps[] can't go away.
Now that ptrace_get_breakpoints/ptrace_put_breakpoints have no callers,
we can kill them and remove task->ptrace_bp_refcnt.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Michael Neuling <mikey@neuling.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
commit 95913d97914f44db2b81271c2e2ebd4d2ac2df83 upstream.
So the problem this patch is trying to address is as follows:
CPU0 CPU1
context_switch(A, B)
ttwu(A)
LOCK A->pi_lock
A->on_cpu == 0
finish_task_switch(A)
prev_state = A->state <-.
WMB |
A->on_cpu = 0; |
UNLOCK rq0->lock |
| context_switch(C, A)
`-- A->state = TASK_DEAD
prev_state == TASK_DEAD
put_task_struct(A)
context_switch(A, C)
finish_task_switch(A)
A->state == TASK_DEAD
put_task_struct(A)
The argument being that the WMB will allow the load of A->state on CPU0
to cross over and observe CPU1's store of A->state, which will then
result in a double-drop and use-after-free.
Now the comment states (and this was true once upon a long time ago)
that we need to observe A->state while holding rq->lock because that
will order us against the wakeup; however the wakeup will not in fact
acquire (that) rq->lock; it takes A->pi_lock these days.
We can obviously fix this by upgrading the WMB to an MB, but that is
expensive, so we'd rather avoid that.
The alternative this patch takes is: smp_store_release(&A->on_cpu, 0),
which avoids the MB on some archs, but not important ones like ARM.
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: manfred@colorfullife.com
Cc: will.deacon@arm.com
Fixes: e4a52bcb9a ("sched: Remove rq->lock from the first half of ttwu()")
Link: http://lkml.kernel.org/r/20150929124509.GG3816@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
commit 3245d6acab981a2388ffb877c7ecc97e763c59d4 upstream.
wait_consider_task() checks EXIT_ZOMBIE after EXIT_DEAD/EXIT_TRACE and
both checks can fail if we race with EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE
change in between, gcc needs to reload p->exit_state after
security_task_wait(). In this case ->notask_error will be wrongly
cleared and do_wait() can hang forever if it was the last eligible
child.
Many thanks to Arne who carefully investigated the problem.
Note: this bug is very old but it was pure theoretical until commit
b3ab03160dfa ("wait: completely ignore the EXIT_DEAD tasks"). Before
this commit "-O2" was probably enough to guarantee that compiler won't
read ->exit_state twice.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Arne Goedeke <el@laramies.com>
Tested-by: Arne Goedeke <el@laramies.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
