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ARM: 8087/1: ptrace: reload syscall number after secure_computing() check

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On the syscall tracing path, we call out to secure_computing() to allow
seccomp to check the syscall number being attempted. As part of this, a
SIGTRAP may be sent to the tracer and the syscall could be re-written by
a subsequent SET_SYSCALL ptrace request. Unfortunately, this new syscall
is ignored by the current code unless TIF_SYSCALL_TRACE is also set on
the current thread.

This patch slightly reworks the enter path of the syscall tracing code
so that we always reload the syscall number from
current_thread_info()->syscall after the potential ptrace traps.

Acked-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: 41900903483eb96602dd72e719a798c208118aad
Git-repo: https://android.googlesource.com/kernel/common.git
Signed-off-by: Ian Maund <imaund@codeaurora.org>
This commit is contained in:
Will Deacon 2014-06-27 17:01:47 +01:00 committed by Ian Maund
parent 6a8bb76f8e
commit 22ade14c47
1 changed files with 4 additions and 3 deletions
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7
arch/arm/kernel/ptrace.c
View file

@ -916,7 +916,7 @@ enum ptrace_syscall_dir {
PTRACE_SYSCALL_EXIT,
};
static int tracehook_report_syscall(struct pt_regs *regs,
static void tracehook_report_syscall(struct pt_regs *regs,
enum ptrace_syscall_dir dir)
{
unsigned long ip;
@ -934,7 +934,6 @@ static int tracehook_report_syscall(struct pt_regs *regs,
current_thread_info()->syscall = -1;
regs->ARM_ip = ip;
return current_thread_info()->syscall;
}
asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
@ -946,7 +945,9 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
return -1;
if (test_thread_flag(TIF_SYSCALL_TRACE))
scno = tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
scno = current_thread_info()->syscall;
if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
trace_sys_enter(regs, scno);