From a980300e27c138836e2cc515e53f83e4d1a0505b Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 13 Aug 2010 13:46:26 -0700 Subject: [PATCH] x86: don't send SIGBUS for kernel page faults Based on commit 96054569190bdec375fe824e48ca1f4e3b53dd36 upstream, authored by Linus Torvalds. This is my backport to the .27 kernel tree, hopefully preserving the same functionality. Original commit message: It's wrong for several reasons, but the most direct one is that the fault may be for the stack accesses to set up a previous SIGBUS. When we have a kernel exception, the kernel exception handler does all the fixups, not some user-level signal handler. Even apart from the nested SIGBUS issue, it's also wrong to give out kernel fault addresses in the signal handler info block, or to send a SIGBUS when a system call already returns EFAULT. Cc: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/fault.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 33842556ce708..9d3c576a6b2e8 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -589,6 +589,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code) unsigned long address; int write, si_code; int fault; + int should_exit_no_context = 0; #ifdef CONFIG_X86_64 unsigned long flags; #endif @@ -876,6 +877,9 @@ no_context: oops_end(flags, regs, SIGKILL); #endif + if (should_exit_no_context) + return; + /* * We ran out of memory, or some other thing happened to us that made * us unable to handle the page fault gracefully. @@ -901,8 +905,11 @@ do_sigbus: up_read(&mm->mmap_sem); /* Kernel mode? Handle exceptions or die */ - if (!(error_code & PF_USER)) + if (!(error_code & PF_USER)) { + should_exit_no_context = 1; goto no_context; + } + #ifdef CONFIG_X86_32 /* User space => ok to do another page fault */ if (is_prefetch(regs, address, error_code)) -- 2.47.3