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Vineet Gupta 40a894023d ARC: Incorrect mm reference used in vmalloc fault handler 
commit 9c41f4eeb9 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 20bafb3d23
   "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>
2013-11-13 12:05:32 +09:00
..
boot ARC: [TB10x] Remove redundant abilis,simple-pinctrl mechanism 2013-05-15 10:12:03 +05:30
configs ARC: Add support for nSIM OSCI System C model 2013-05-07 13:44:00 +05:30
include ARC: Workaround spinlock livelock in SMP SystemC simulation 2013-10-18 07:45:45 -07:00
kernel ARC: Ignore ptrace SETREGSET request for synthetic register "stop_pc" 2013-10-18 07:45:45 -07:00
lib ARC: [lib] strchr breakage in Big-endian configuration 2013-08-29 09:47:34 -07:00
mm ARC: Incorrect mm reference used in vmalloc fault handler 2013-11-13 12:05:32 +09:00
oprofile ARC: OProfile support 2013-02-15 23:16:00 +05:30
plat-arcfpga ARC port updates for Linux 3.10 (part 1) 2013-05-09 14:36:27 -07:00
plat-tb10x ARC: [TB10x] Remove redundant abilis,simple-pinctrl mechanism 2013-05-15 10:12:03 +05:30
Kbuild
Kconfig ARC: [mm] Aliasing VIPT dcache support 2/4 2013-05-09 21:59:46 +05:30
Kconfig.debug
Makefile ARC: [TB10x] Add support for TB10x platform 2013-05-07 13:43:59 +05:30