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    Subject[PATCH 3.12 036/111] ARM: fix missing syscall trace exit
    Date
    From: Russell King <rmk+kernel@arm.linux.org.uk>

    3.12-stable review patch. If anyone has any objections, please let me know.

    ===============

    commit 1b97937246d8b97c0760d16d8992c7937bdf5e6a upstream.

    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>
    Signed-off-by: Jiri Slaby <jslaby@suse.cz>
    ---
    arch/arm/kernel/entry-common.S | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
    index bc6bd9683ba4..c70b4e195d2e 100644
    --- a/arch/arm/kernel/entry-common.S
    +++ b/arch/arm/kernel/entry-common.S
    @@ -32,7 +32,9 @@ 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
    --
    2.4.2


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