* [PATCH] ARC: Incorrect mm reference used in vmalloc fault handler
2013-11-02 12:17 [PATCH] Critical ARC Fix for 3.12 Vineet Gupta
@ 2013-11-02 12:17 ` Vineet Gupta
2013-11-03 10:29 ` [PATCH] Critical ARC Fix for 3.12 Geert Uytterhoeven
1 sibling, 0 replies; 5+ messages in thread
From: Vineet Gupta @ 2013-11-02 12:17 UTC (permalink / raw)
To: Linus Torvalds
Cc: lkml, Gilad Ben-Yossef, Noam Camus, Peter Hurley, Vineet Gupta,
stable
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>
Cc: linux-kernel@vger.kernel.org
---
arch/arc/mm/fault.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 81554ded1260..9c69552350c4 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(unsigned long address, struct pt_regs *regs)
* 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
--
1.8.1.2
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] Critical ARC Fix for 3.12
2013-11-02 12:17 [PATCH] Critical ARC Fix for 3.12 Vineet Gupta
2013-11-02 12:17 ` [PATCH] ARC: Incorrect mm reference used in vmalloc fault handler Vineet Gupta
@ 2013-11-03 10:29 ` Geert Uytterhoeven
2013-11-05 7:03 ` Vineet Gupta
2013-11-09 5:29 ` Greg KH
1 sibling, 2 replies; 5+ messages in thread
From: Geert Uytterhoeven @ 2013-11-03 10:29 UTC (permalink / raw)
To: Vineet Gupta
Cc: Linus Torvalds, lkml, Gilad Ben-Yossef, Noam Camus, Peter Hurley,
stable
Added CC stable, so Greg will see it.
Added commit 9c41f4eeb9d51f3ece20428d35a3ea32cf3b5622, so Greg knows
what to cherry-pick.
On Sat, Nov 2, 2013 at 1:17 PM, Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote:
> Hi Linus,
>
> Sorry for this extemely late patch for 3.12 but it causes a SMP build of ARC
> to panic in boot.
>
> Greg, the patch as it is doesn't apply to 3.10 (but does to 3.11). So can you
> please queue it up for 3.11 and I'll send a fixup for 3.10.
>
> Thx,
> -Vineet
>
>
> Vineet Gupta (1):
> ARC: Incorrect mm reference used in vmalloc fault handler
>
> arch/arc/mm/fault.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 5+ messages in thread