From: Greg KH on
2.6.27-stable review patch. If anyone has any objections, please let us know.


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 <torvalds(a)>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)>

arch/x86/mm/fault.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -589,6 +589,7 @@ void __kprobes do_page_fault(struct pt_r
unsigned long address;
int write, si_code;
int fault;
+ int should_exit_no_context = 0;
#ifdef CONFIG_X86_64
unsigned long flags;
@@ -876,6 +877,9 @@ no_context:
oops_end(flags, regs, SIGKILL);

+ 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:

/* 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))

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