diff options
| author | Roland McGrath <roland@redhat.com> | 2010-09-14 12:22:58 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-09-20 13:03:22 -0700 |
| commit | 1b159e074a425d80c9cff0f19404a9fbe83140a5 (patch) | |
| tree | 35b2cf87f52c6366aa9e4bbe138cdb7d1c9d5c21 | |
| parent | 7a0e4cc1437156ac650b52653f1cd244ecfe0598 (diff) | |
x86-64, compat: Retruncate rax after ia32 syscall entry tracing
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>
| -rw-r--r-- | arch/x86/ia32/ia32entry.S | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index bb59ef329d5..745bab210f3 100644 --- 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 |