enable interrupts in user path of page fault.
This is a minor fix, but what is currently there is essentially wrong.
In do_page_fault, if the faulting address from user code happens to be
in kernel address space (int *p = (int*)-1; p = 0xbed;) then the
do_page_fault handler will jump over the local_irq_enable with the
goto bad_area_nosemaphore;
But the first line there sees this is user code and goes through the
process of sending a signal to send SIGSEGV to the user task. This whole
time interrupts are disabled and the task can not be preempted by a
higher priority task.
This patch always enables interrupts in the user path of the
bad_area_nosemaphore.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index bfb62a1..635e58d 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -476,6 +476,12 @@
bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */
if (error_code & PF_USER) {
+
+ /*
+ * It's possible to have interrupts off here.
+ */
+ local_irq_enable();
+
if (is_prefetch(regs, address, error_code))
return;