lkml.org 
[lkml]   [2010]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[102/129] x86-64, compat: Retruncate rax after ia32 syscall entry tracing
2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Roland McGrath <roland@redhat.com>

commit eefdca043e8391dcd719711716492063030b55ac upstream.

In commit d4d6715, we reopened an old hole for a 64-bit ptracer touching a
32-bit tracee in system call entry. A %rax value set via ptrace at the
entry tracing stop gets used whole as a 32-bit syscall number, while we
only check the low 32 bits for validity.

Fix it by truncating %rax back to 32 bits after syscall_trace_enter,
in addition to testing the full 64 bits as has already been added.

Reported-by: Ben Hawkes <hawkes@sota.gen.nz>
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/ia32/ia32entry.S | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -50,7 +50,12 @@
/*
* Reload arg registers from stack in case ptrace changed them.
* We don't reload %eax because syscall_trace_enter() returned
- * the value it wants us to use in the table lookup.
+ * the %rax value we should see. Instead, we just truncate that
+ * value to 32 bits again as we did on entry from user mode.
+ * If it's a new value set by user_regset during entry tracing,
+ * this matches the normal truncation of the user-mode value.
+ * If it's -1 to make us punt the syscall, then (u32)-1 is still
+ * an appropriately invalid value.
*/
.macro LOAD_ARGS32 offset, _r9=0
.if \_r9
@@ -60,6 +65,7 @@
movl \offset+48(%rsp),%edx
movl \offset+56(%rsp),%esi
movl \offset+64(%rsp),%edi
+ movl %eax,%eax /* zero extension */
.endm

.macro CFI_STARTPROC32 simple



\
 
 \ /
  Last update: 2010-09-18 21:25    [from the cache]
©2003-2011 Jasper Spaans