diff options
| author | Andy Lutomirski <[email protected]> | 2016-02-23 13:19:29 -0800 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2016-02-24 08:43:04 +0100 |
| commit | 04d1d281dcfe683a53cddfab8371fc8bb302b069 (patch) | |
| tree | 8622a05e522fea41d855fa8b0177777203fb491d | |
| parent | dd71a17b1193dd4a4c35ecd0ba227aac3d110836 (diff) | |
x86/entry/32: Add an ASM_CLAC to entry_SYSENTER_32
Both before and after 5f310f739b4c ("x86/entry/32: Re-implement
SYSENTER using the new C path"), we relied on a uaccess very early
in the SYSENTER path to clear AC. After that change, though, we can
potentially make it all the way into C code with AC set, which
enlarges the attack surface for SMAP bypass by doing SYSENTER with
AC set.
Strengthen the SMAP protection by addding the missing ASM_CLAC right
at the beginning.
Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/3e36be110724896e32a4a1fe73bacb349d3cba94.1456262295.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>
| -rw-r--r-- | arch/x86/entry/entry_32.S | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 77d8c5112900..bb3e376d0f33 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -294,6 +294,7 @@ sysenter_past_esp: pushl $__USER_DS /* pt_regs->ss */ pushl %ebp /* pt_regs->sp (stashed in bp) */ pushfl /* pt_regs->flags (except IF = 0) */ + ASM_CLAC /* Clear AC after saving FLAGS */ orl $X86_EFLAGS_IF, (%esp) /* Fix IF */ pushl $__USER_CS /* pt_regs->cs */ pushl $0 /* pt_regs->ip = 0 (placeholder) */ |