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ARM: fix missing syscall trace exit

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Josh Stone reports:

  I've discovered a case where both arm and arm64 will miss a ptrace
  syscall-exit that they should report.  If the syscall is entered
  without TIF_SYSCALL_TRACE set, then it goes on the fast path.  It's
  then possible to have TIF_SYSCALL_TRACE added in the middle of the
  syscall, but ret_fast_syscall doesn't check this flag again.

Fix this by always checking for a syscall trace in the fast exit path.

Reported-by: Josh Stone <jistone@redhat.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-05-15 11:02:23 +01:00
parent 965278dcb8
commit 1b97937246
1 changed files with 3 additions and 1 deletions
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4
arch/arm/kernel/entry-common.S
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@ -33,7 +33,9 @@ ret_fast_syscall:
UNWIND(.fnstart )
UNWIND(.cantunwind )
disable_irq @ disable interrupts
ldr r1, [tsk, #TI_FLAGS]
ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing
tst r1, #_TIF_SYSCALL_WORK
bne __sys_trace_return
tst r1, #_TIF_WORK_MASK
bne fast_work_pending
asm_trace_hardirqs_on