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BACKPORT: Sanitize 'move_pages()' permission checks
The 'move_paghes()' system call was introduced long long ago with the same permission checks as for sending a signal (except using CAP_SYS_NICE instead of CAP_SYS_KILL for the overriding capability). That turns out to not be a great choice - while the system call really only moves physical page allocations around (and you need other capabilities to do a lot of it), you can check the return value to map out some the virtual address choices and defeat ASLR of a binary that still shares your uid. So change the access checks to the more common 'ptrace_may_access()' model instead. This tightens the access checks for the uid, and also effectively changes the CAP_SYS_NICE check to CAP_SYS_PTRACE, but it's unlikely that anybody really _uses_ this legacy system call any more (we hav ebetter NUMA placement models these days), so I expect nobody to notice. Famous last words. Reported-by: Otto Ebeling <otto.ebeling@iki.fi> Acked-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Willy Tarreau <w@1wt.eu> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> cherry-picked from: 197e7e521384a23b9e585178f3f11c9fa08274b9 This branch does not have the PTRACE_MODE_REALCREDS flag but its default behavior is the same as PTRACE_MODE_REALCREDS. So use PTRACE_MODE_READ instead of PTRACE_MODE_READ_REALCREDS. Change-Id: I75364561d91155c01f78dd62cdd41c5f0f418854
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parent
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1 changed files with 3 additions and 8 deletions
11
mm/migrate.c
11
mm/migrate.c
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@ -38,6 +38,7 @@
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#include <linux/gfp.h>
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#include <linux/balloon_compaction.h>
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#include <trace/events/kmem.h>
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#include <linux/ptrace.h>
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#include <asm/tlbflush.h>
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@ -1396,7 +1397,6 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
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const int __user *, nodes,
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int __user *, status, int, flags)
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{
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const struct cred *cred = current_cred(), *tcred;
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struct task_struct *task;
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struct mm_struct *mm;
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int err;
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@ -1420,14 +1420,9 @@ SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
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/*
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* Check if this process has the right to modify the specified
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* process. The right exists if the process has administrative
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* capabilities, superuser privileges or the same
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* userid as the target process.
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* process. Use the regular "ptrace_may_access()" checks.
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*/
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tcred = __task_cred(task);
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if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) &&
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!uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) &&
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!capable(CAP_SYS_NICE)) {
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if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
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rcu_read_unlock();
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err = -EPERM;
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goto out;
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