ARM: 7487/1: mm: avoid setting nG bit for user mappings that aren't present
commit47f1204329237a0f8655f5a9f14a38ac81946ca1
authorWill Deacon <will.deacon@arm.com>
Fri, 10 Aug 2012 16:51:18 +0000 (10 17:51 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Sat, 11 Aug 2012 08:15:59 +0000 (11 09:15 +0100)
tree863782a6d372973865860a3e55d79a0cbd01880d
parent237ec6f2e51d2fc2ff37c7c5f1ccc9264d09c85b
ARM: 7487/1: mm: avoid setting nG bit for user mappings that aren't present

Swap entries are encoding in ptes such that !pte_present(pte) and
pte_file(pte). The remaining bits of the descriptor are used to identify
the swapfile and offset within it to the swap entry.

When writing such a pte for a user virtual address, set_pte_at
unconditionally sets the nG bit, which (in the case of LPAE) will
corrupt the swapfile offset and lead to a BUG:

[  140.494067] swap_free: Unused swap offset entry 000763b4
[  140.509989] BUG: Bad page map in process rs:main Q:Reg  pte:0ec76800 pmd:8f92e003

This patch fixes the problem by only setting the nG bit for user
mappings that are actually present.

Cc: <stable@vger.kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
arch/arm/include/asm/pgtable.h
arch/arm/mm/flush.c