[PATCH] arm64: fix missing syscall trace exit
will.deacon at arm.com
Mon Jun 8 03:21:05 PDT 2015
Thanks for the patch.
On Fri, Jun 05, 2015 at 10:28:03PM +0100, Josh Stone wrote:
> If a 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. This causes a ptrace syscall-exit-stop to be missed.
> For instance, from a PTRACE_EVENT_FORK reported during do_fork, the
> tracer might resume with PTRACE_SYSCALL, setting TIF_SYSCALL_TRACE.
> Now the completion of the fork should have a syscall-exit-stop.
> Russell King fixed this on arm by re-checking _TIF_SYSCALL_WORK in the
> fast exit path. Do the same on arm64.
> v2: Re-enable interrupts before branching to __sys_trace_return.
Please don't include the changelog in the commit message.
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will.deacon at arm.com>
> Cc: Russell King <rmk+kernel at arm.linux.org.uk>
> Signed-off-by: Josh Stone <jistone at redhat.com>
> arch/arm64/kernel/entry.S | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 959fe8733560..988bea43dc74 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -608,11 +608,16 @@ ENDPROC(cpu_switch_to)
> disable_irq // disable interrupts
> - ldr x1, [tsk, #TI_FLAGS]
> + ldr x1, [tsk, #TI_FLAGS] // re-check for syscall tracing
> + and x2, x1, #_TIF_SYSCALL_WORK
> + cbnz x2, ret_fast_syscall_trace
> and x2, x1, #_TIF_WORK_MASK
> cbnz x2, fast_work_pending
> enable_step_tsk x1, x2
> kernel_exit 0, ret = 1
> + enable_irq // enable interrupts
> + b __sys_trace_return
Looks good to me:
Reviewed-by: Will Deacon <will.deacon at arm.com>
I assume this can wait until 4.2?
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