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authorKees Cook <keescook@chromium.org>2013-02-07 17:44:13 (GMT)
committerIngo Molnar <mingo@kernel.org>2013-02-07 18:57:44 (GMT)
commite575a86fdc50d013bf3ad3aa81d9100e8e6cc60d (patch)
tree04caac94b924d2a3a084f348b999f790f625b09f /arch
parentbb9b1a834f7a916a65ba64f4812078cfbe2f4fc4 (diff)
downloadlinux-e575a86fdc50d013bf3ad3aa81d9100e8e6cc60d.tar.xz
x86: Do not leak kernel page mapping locations
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> Cc: stable@vger.kernel.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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/fault.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 027088f..fb674fd 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -748,13 +748,15 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
return;
}
#endif
+ /* Kernel addresses are always protection faults: */
+ if (address >= TASK_SIZE)
+ error_code |= PF_PROT;
- if (unlikely(show_unhandled_signals))
+ 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_nr = X86_TRAP_PF;
force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0);