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| author | Vineet Gupta <Vineet.Gupta1@synopsys.com> | 2013-11-02 17:47:49 +0530 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-11-02 10:27:04 -0700 |
| commit | 9c41f4eeb9d51f3ece20428d35a3ea32cf3b5622 (patch) | |
| tree | 18750e6cadeacd1bcb5e7e1b0ccf49ec6b9396de | |
| parent | 9581b7d2689ad9a0a20ddaec0427b46ad774585b (diff) | |
| download | linux-9c41f4eeb9d51f3ece20428d35a3ea32cf3b5622.tar.bz2 | |
ARC: Incorrect mm reference used in vmalloc fault handler
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: stable@vger.kernel.org #3.10 and 3.11
Cc: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/arc/mm/fault.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index d63f3de0cd5b..0c14d8a52683 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -17,7 +17,7 @@ #include <asm/pgalloc.h> #include <asm/mmu.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 @@ -27,7 +27,7 @@ static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) pud_t *pud, *pud_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); if (!pgd_present(*pgd_k)) @@ -72,7 +72,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address) * nothing more. */ if (address >= VMALLOC_START && address <= VMALLOC_END) { - ret = handle_vmalloc_fault(mm, address); + ret = handle_vmalloc_fault(address); if (unlikely(ret)) goto bad_area_nosemaphore; else |