3.2-stable review patch. If anyone has any objections, please let me know.
------------------ From: Kees Cook <[email protected]> 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 <[email protected]> Suggested-by: Brad Spengler <[email protected]> Signed-off-by: Kees Cook <[email protected]> Acked-by: H. Peter Anvin <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Eric W. Biederman <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <[email protected]> --- arch/x86/mm/fault.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -738,13 +738,15 @@ __bad_area_nosemaphore(struct pt_regs *r 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
