This is a note to let you know that I've just added the patch titled
x86: Do not leak kernel page mapping locations
to the 3.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-do-not-leak-kernel-page-mapping-locations.patch
and it can be found in the queue-3.0 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e575a86fdc50d013bf3ad3aa81d9100e8e6cc60d Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@xxxxxxxxxxxx>
Date: Thu, 7 Feb 2013 09:44:13 -0800
Subject: x86: Do not leak kernel page mapping locations
From: Kees Cook <keescook@xxxxxxxxxxxx>
commit e575a86fdc50d013bf3ad3aa81d9100e8e6cc60d upstream.
Without this patch, it is trivial to determine kernel page
mappings by examining the error code reported to dmesg[1].
Instead, declare the entire kernel memory space as a violation
of a present page.
Additionally, since show_unhandled_signals is enabled by
default, switch branch hinting to the more realistic
expectation, and unobfuscate the setting of the PF_PROT bit to
improve readability.
[1] http://vulnfactory.org/blog/2013/02/06/a-linux-memory-trick/
Reported-by: Dan Rosenberg <dan.j.rosenberg@xxxxxxxxx>
Suggested-by: Brad Spengler <spender@xxxxxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Acked-by: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Link: http://lkml.kernel.org/r/20130207174413.GA12485@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: CAI Qian <caiqian@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/mm/fault.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -720,12 +720,15 @@ __bad_area_nosemaphore(struct pt_regs *r
if (is_errata100(regs, address))
return;
- if (unlikely(show_unhandled_signals))
+ /* Kernel addresses are always protection faults: */
+ if (address >= TASK_SIZE)
+ error_code |= PF_PROT;
+
+ if (likely(show_unhandled_signals))
show_signal_msg(regs, error_code, address, tsk);
- /* Kernel addresses are always protection faults: */
tsk->thread.cr2 = address;
- tsk->thread.error_code = error_code | (address >= TASK_SIZE);
+ tsk->thread.error_code = error_code;
tsk->thread.trap_no = 14;
force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);
Patches currently in stable-queue which might be from keescook@xxxxxxxxxxxx are
queue-3.0/x86-do-not-leak-kernel-page-mapping-locations.patch
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