https://github.com/torvalds/linux
Revision 653bc77af60911ead1f423e588f54fc2547c4957 authored by Andy Lutomirski on 01 November 2014, 01:08:45 UTC, committed by Linus Torvalds on 01 November 2014, 01:47:09 UTC
Rusty noticed a Really Bad Bug (tm) in my NT fix.  The entry code
reads out of bounds, causing the NT fix to be unreliable.  But, and
this is much, much worse, if your stack is somehow just below the
top of the direct map (or a hole), you read out of bounds and crash.

Excerpt from the crash:

[    1.129513] RSP: 0018:ffff88001da4bf88  EFLAGS: 00010296

  2b:*    f7 84 24 90 00 00 00     testl  $0x4000,0x90(%rsp)

That read is deterministically above the top of the stack.  I
thought I even single-stepped through this code when I wrote it to
check the offset, but I clearly screwed it up.

Fixes: 8c7aa698baca ("x86_64, entry: Filter RFLAGS.NT on entry from userspace")
Reported-by: Rusty Russell <rusty@ozlabs.org>
Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 32e8fd2
History
Tip revision: 653bc77af60911ead1f423e588f54fc2547c4957 authored by Andy Lutomirski on 01 November 2014, 01:08:45 UTC
x86_64, entry: Fix out of bounds read on sysenter
Tip revision: 653bc77
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