Commit e575a86f authored by Kees Cook's avatar Kees Cook Committed by Ingo Molnar
Browse files

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: default avatarDan Rosenberg <dan.j.rosenberg@gmail.com>
Suggested-by: default avatarBrad Spengler <spender@grsecurity.net>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Acked-by: default avatarH. 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: default avatarIngo Molnar <mingo@kernel.org>
parent bb9b1a83
......@@ -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);
......
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