diff options
| author | Kees Cook <keescook@chromium.org> | 2013-02-07 09:44:13 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-03-06 03:23:51 +0000 |
| commit | d8db3e2260deb9f5007f2d663fd9d767746cf139 (patch) | |
| tree | b75ffbfc0aff8c0c431f095a39f922d05674e958 /arch/x86/mm | |
| parent | 901fe4bb2a69121c1c405db935398b314d8343cd (diff) | |
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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86/mm')
| -rw-r--r-- | arch/x86/mm/fault.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 5db0490deb0..7b73c884a7e 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -738,13 +738,15 @@ __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_no = 14; force_sig_info_fault(SIGSEGV, si_code, address, tsk, 0); |