On Wed, May 16, 2018 at 12:43:37AM +0300, Alexey Dobriyan wrote:
> On Tue, May 15, 2018 at 09:25:53PM +0000, Anvin, H Peter wrote:
> > Why is that a problem?
> > Code: 00 00 00 eb e6 cc cc cc cc cc cc cc cc cc cc cc cc cc fa 8d b6 00 00
> > 00 00 e8 5d e8 8f ff 8b 44 24 34 83 e0 03 83 f8 03 72 28 cc <cc> cc
> > cc cc cc cc cc fa 8d b6 00 00 00 00 e8 3d e8 8f ff 89 e0
> >
> > EIP: ret_from_intr+0xd/0x14 SS:ESP: 0068:8603bfb4
> >
> > INT3 slipped through M586 => X86_ALIGNMENT_16 :-\
>
> I could make the patch x86_64 only, but!
>
> It crashed into the middle of the padding.
>
> 796ef8fc <ret_from_intr>:
> 796ef8fc: 8b 44 24 34 mov eax,DWORD PTR [esp+0x34]
> 796ef900: 83 e0 03 and eax,0x3
> 796ef903: 83 f8 03 cmp eax,0x3
> 796ef906: 72 28 jb 796ef930 <resume_kernel>
> 796ef908: cc int3
> 796ef909: cc <========> int3
> 796ef90a: cc int3
> 796ef90b: cc int3
> 796ef90c: cc int3
> 796ef90d: cc int3
> 796ef90e: cc int3
> 796ef90f: cc int3
The padding isn't needed there, and the resume_userspace symbol is never
used, so wouldn't this fix it?
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index bef8e2b202a8..9e56243c984c 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -338,7 +338,6 @@ ret_from_intr:
cmpl $USER_RPL, %eax
jb resume_kernel # not returning to v8086 or
userspace
-ENTRY(resume_userspace)
DISABLE_INTERRUPTS(CLBR_ANY)
TRACE_IRQS_OFF
movl %esp, %eax
