Commit 554086d8 authored Jun 23, 2014 by Andy Lutomirski Committed by H. Peter Anvin Jun 23, 2014

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



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:
af0575bb 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>

parent dda1e95c

arch/x86/kernel/entry_32.S

+8 −2

Original line number	Diff line number	Diff line
		@@ -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