linux-kernel - [PATCH 3.12 036/111] ARM: fix missing syscall trace exit

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Message-Id: <bd7044dfd8a3bcfd386d2cd7f0c01ba884a2cc88.1433943052.git.jslaby@suse.cz>
Date:	Wed, 10 Jun 2015 17:26:25 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Russell King <rmk+kernel@....linux.org.uk>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 036/111] ARM: fix missing syscall trace exit

From: Russell King <rmk+kernel@....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@...hat.com>
Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@...e.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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