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 <[email protected]>
diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c
index 29d7d61..1ecb3e4 100644
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -458,6 +458,11 @@ bad_area:
bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */
if (error_code & 4) {
+ /*
+ * It's possible to have interrupts off here.
+ */
+ local_irq_enable();
+
/*
* Valid to do another page fault here because this one came
* from user space.
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:
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;
-
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