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ARC: Incorrect mm reference used in vmalloc fault handler

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commit 9c41f4eeb9d51f3ece20428d35a3ea32cf3b5622 upstream.

A vmalloc fault needs to sync up PGD/PTE entry from init_mm to current
task's "active_mm".  ARC vmalloc fault handler however was using mm.

A vmalloc fault for non user task context (actually pre-userland, from
init thread's open for /dev/console) caused the handler to deref NULL mm
(for mm->pgd)

The reasons it worked so far is amazing:

1. By default (!SMP), vmalloc fault handler uses a cached value of PGD.
   In SMP that MMU register is repurposed hence need for mm pointer deref.

2. In pre-3.12 SMP kernel, the problem triggering vmalloc didn't exist in
   pre-userland code path - it was introduced with commit 20bafb3d23d108bc
   "n_tty: Move buffers into n_tty_data"

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Noam Camus <noamc@ezchip.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Vineet Gupta 2013-11-02 17:47:49 +05:30 committed by Greg Kroah-Hartman
parent 27b840ea21
commit 40a894023d
1 changed files with 3 additions and 3 deletions
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6
arch/arc/mm/fault.c
View file

@ -16,7 +16,7 @@
#include <linux/kdebug.h> #include <linux/kdebug.h>
#include <asm/pgalloc.h> #include <asm/pgalloc.h>
static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) static int handle_vmalloc_fault(unsigned long address)
{ {
/* /*
* Synchronize this task's top level page-table * Synchronize this task's top level page-table
@ -26,7 +26,7 @@ static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address)
pud_t *pud, *pud_k; pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k; pmd_t *pmd, *pmd_k;
pgd = pgd_offset_fast(mm, address); pgd = pgd_offset_fast(current->active_mm, address);
pgd_k = pgd_offset_k(address); pgd_k = pgd_offset_k(address);
if (!pgd_present(*pgd_k)) if (!pgd_present(*pgd_k))
@ -72,7 +72,7 @@ void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
* nothing more. * nothing more.
*/ */
if (address >= VMALLOC_START && address <= VMALLOC_END) { if (address >= VMALLOC_START && address <= VMALLOC_END) {
ret = handle_vmalloc_fault(mm, address); ret = handle_vmalloc_fault(address);
if (unlikely(ret)) if (unlikely(ret))
goto bad_area_nosemaphore; goto bad_area_nosemaphore;
else else