x86-64: fix int $0x80 -ENOSYS return

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>

	int
	main (void)
	{
	  long res;
	  asm ("int $0x80" : "=a" (res) : "0" (99999));
	  printf ("bad syscall returns %ld\n", 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>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 256b00b61892..5a0d76dc56a4 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
-ia32_do_syscall:        
         cmpl $(IA32_NR_syscalls-1),%eax
-        ja  int_ret_from_sys_call       /* ia32_tracesys has set RAX(%rsp) */
+        ja ia32_badsys
+ia32_do_call:
         IA32_ARG_FIXUP
         call *ia32_sys_call_table(,%rax,8) # xxx: rip relative
 ia32_sysret:
@@ -435,7 +435,9 @@ ia32_tracesys:
         call syscall_trace_enter
         LOAD_ARGS32 ARGOFFSET  /* reload args from stack in case ptrace changed it */
         RESTORE_REST
-        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
 END(ia32_syscall)
 
 ia32_badsys: