From f39edfbf6dbf8e29cfbafd67d93fa1e30196701c Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 7 Feb 2013 09:44:13 -0800 Subject: 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 Suggested-by: Brad Spengler Signed-off-by: Kees Cook Acked-by: H. Peter Anvin Cc: Paul E. McKenney Cc: Frederic Weisbecker Cc: Eric W. Biederman Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20130207174413.GA12485@www.outflux.net Signed-off-by: Ingo Molnar Signed-off-by: CAI Qian Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/fault.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'arch/x86') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 2dbf6bf..3b2ad91 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); -- cgit v1.1