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x86_32, entry: Do syscall exit work on badsys (CVE-2014-4508)

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The bad syscall nr paths are their own incomprehensible route
through the entry control flow.  Rearrange them to work just like
syscalls that return -ENOSYS.

This fixes an OOPS in the audit code when fast-path auditing is
enabled and sysenter gets a bad syscall nr (CVE-2014-4508).

This has probably been broken since Linux 2.6.27:
af0575bba0 i386 syscall audit fast-path

Cc: stable@vger.kernel.org
Cc: Roland McGrath <roland@redhat.com>
Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/e09c499eade6fc321266dd6b54da7beb28d6991c.1403558229.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Andy Lutomirski 2014-06-23 14:22:15 -07:00 committed by H. Peter Anvin
parent dda1e95cee
commit 554086d85e
1 changed files with 8 additions and 2 deletions
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10
arch/x86/kernel/entry_32.S
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@ -423,9 +423,10 @@ sysenter_past_esp:
jnz sysenter_audit
sysenter_do_call:
cmpl $(NR_syscalls), %eax
jae syscall_badsys
jae sysenter_badsys
call *sys_call_table(,%eax,4)
movl %eax,PT_EAX(%esp)
sysenter_after_call:
LOCKDEP_SYS_EXIT
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
@ -675,7 +676,12 @@ END(syscall_fault)
syscall_badsys:
movl $-ENOSYS,PT_EAX(%esp)
jmp resume_userspace
jmp syscall_exit
END(syscall_badsys)
sysenter_badsys:
movl $-ENOSYS,PT_EAX(%esp)
jmp sysenter_after_call
END(syscall_badsys)
CFI_ENDPROC