Patch "ARM: fix missing syscall trace exit" has been added to the 3.14-stable tree

Patch "ARM: fix missing syscall trace exit" has been added to the 3.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    ARM: fix missing syscall trace exit

to the 3.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-fix-missing-syscall-trace-exit.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 1b97937246d8b97c0760d16d8992c7937bdf5e6a Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Fri, 15 May 2015 11:02:23 +0100
Subject: ARM: fix missing syscall trace exit

From: Russell King <rmk+kernel@arm.linux.org.uk>

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/kernel/entry-common.S |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- 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


Patches currently in stable-queue which might be from rmk+kernel@arm.linux.org.uk are

queue-3.14/arm-fix-missing-syscall-trace-exit.patch