Commit-ID: e575a86fdc50d013bf3ad3aa81d9100e8e6cc60d Gitweb: http://git.kernel.org/tip/e575a86fdc50d013bf3ad3aa81d9100e8e6cc60d Author: Kees Cook <keescook@xxxxxxxxxxxx> AuthorDate: Thu, 7 Feb 2013 09:44:13 -0800 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Thu, 7 Feb 2013 19:57:44 +0100 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@xxxxxxxxx> Suggested-by: Brad Spengler <spender@xxxxxxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Acked-by: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Link: http://lkml.kernel.org/r/20130207174413.GA12485@xxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/mm/fault.c | 8 +++++--- 1 file 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); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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