Commit e5e3c84b authored by Steven Rostedt's avatar Steven Rostedt Committed by Linus Torvalds
Browse files

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: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c52ecdab
...@@ -458,6 +458,11 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs, ...@@ -458,6 +458,11 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
bad_area_nosemaphore: bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */ /* User mode accesses just cause a SIGSEGV */
if (error_code & 4) { 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 * Valid to do another page fault here because this one came
* from user space. * from user space.
......
...@@ -476,6 +476,12 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, ...@@ -476,6 +476,12 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
bad_area_nosemaphore: bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */ /* User mode accesses just cause a SIGSEGV */
if (error_code & PF_USER) { if (error_code & PF_USER) {
/*
* It's possible to have interrupts off here.
*/
local_irq_enable();
if (is_prefetch(regs, address, error_code)) if (is_prefetch(regs, address, error_code))
return; return;
......
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