[PATCH 07/26] audit: ia32entry.S sign extend error codes when calling 64 bit code

Eric Paris
2011-11-17T22:03:19Z

In the ia32entry syscall exit audit fastpath we have assembly code which calls
__audit_syscall_exit directly. This code was, however, zeroes the upper 32
bits of the return code. It then proceeded to call code which expects longs
to be 64bits long. In order to handle code which expects longs to be 64bit we
sign extend the return code if that code is an error. Thus the
__audit_syscall_exit function can correctly handle using the values in
snprintf("%ld"). This fixes the regression introduced in 5cbf1565f29eb57a86a.

Old record:
type=SYSCALL msg=audit(1306197182.256:281): arch=40000003 syscall=192 success=no exit=4294967283
New record:
type=SYSCALL msg=audit(1306197182.256:281): arch=40000003 syscall=192 success=no exit=-13

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
---

arch/x86/ia32/ia32entry.S | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 1c03202..da8ac87 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -212,7 +212,9 @@ sysexit_from_sys_call:
sti
movl %eax,%esi /* second arg, syscall return value */
cmpl $-MAX_ERRNO,%eax /* is it an error ? */
- setbe %al /* 1 if so, 0 if not */
+ jbe 1f
+ movslq %eax, %rsi /* if error sign extend to 64 bits */
+1: setbe %al /* 1 if error, 0 if not */
movzbl %al,%edi /* zero-extend that into %edi */
call __audit_syscall_exit
GET_THREAD_INFO(%r10)