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Old 02-07-2009, 01:15 AM
Roland McGrath
Default x86-64: fix int $0x80 -ENOSYS return

Bug: #339743

One of my past fixes to this code introduced a different new bug.
When using 32-bit "int $0x80" entry for a bogus syscall number,
the return value is not correctly set to -ENOSYS. This only happens
when neither syscall-audit nor syscall tracing is enabled (i.e., never
seen if auditd ever started). Test program:

/* gcc -o int80-badsys -m32 -g int80-badsys.c
Run on x86-64 kernel.
Note to reproduce the bug you need auditd never to have started. */

#include <errno.h>
#include <stdio.h>

main (void)
long res;
asm ("int $0x80" : "=a" (res) : "0" (99999));
printf ("bad syscall returns %ld
", res);
return res != -ENOSYS;

The fix makes the int $0x80 path match the sysenter and syscall paths.

Reported-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
arch/x86/ia32/ia32entry.S | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 256b00b..5a0d76d 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -418,9 +418,9 @@ ENTRY(ia32_syscall)
orl $TS_COMPAT,TI_status(%r10)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
jnz ia32_tracesys
cmpl $(IA32_NR_syscalls-1),%eax
- ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
+ ja ia32_badsys
call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
@@ -435,7 +435,9 @@ ia32_tracesys:
call syscall_trace_enter
LOAD_ARGS32 ARGOFFSET /* reload args from stack in case ptrace changed it */
- jmp ia32_do_syscall
+ cmpl $(IA32_NR_syscalls-1),%eax
+ ja int_ret_from_sys_call /* ia32_tracesys has set RAX(%rsp) */
+ jmp ia32_do_call


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