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authorKees Cook <keescook@chromium.org>2013-02-07 09:44:13 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-04 06:09:06 +0800
commitf39edfbf6dbf8e29cfbafd67d93fa1e30196701c (patch)
tree3093dd34200fb1f0b4418494554bc62a0d3c796d /arch
parent43f514598ad16af1c6dd08dd429631eaafef7849 (diff)
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x86: Do not leak kernel page mapping locations
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@gmail.com> Suggested-by: Brad Spengler <spender@grsecurity.net> Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: H. Peter Anvin <hpa@zytor.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20130207174413.GA12485@www.outflux.net Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: CAI Qian <caiqian@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/fault.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 2dbf6bf4c7e5..3b2ad913d6ce 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -720,12 +720,15 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
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);