Commit 246f2d2e authored Apr 30, 2014 by H. Peter Anvin

x86-32, espfix: Remove filter for espfix32 due to race

It is not safe to use LAR to filter when to go down the espfix path,
because the LDT is per-process (rather than per-thread) and another
thread might change the descriptors behind our back. Fortunately it
is always *safe* (if a bit slow) to go down the espfix path, and a
32-bit LDT stack segment is extremely rare.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1398816946-3351-1-git-send-email-hpa@linux.intel.com
Cc: <stable@vger.kernel.org> # consider after upstream merge

parent 3891a04a

arch/x86/kernel/entry_32.S

+0 −5

Original line number	Diff line number	Diff line
		@@ -551,11 +551,6 @@ ENTRY(iret_exc)

		CFI_RESTORE_STATE
		ldt_ss:
		larl PT_OLDSS(%esp), %eax
		jnz restore_nocheck
		testl $0x00400000, %eax # returning to 32bit stack?
		jnz restore_nocheck # allright, normal return

		#ifdef CONFIG_PARAVIRT
		/*
		* The kernel can't run on a non-flat stack if paravirt mode