path: root/arch/avr32
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authorMel Gorman <mgorman@suse.de>2012-05-23 12:48:13 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-23 17:57:33 -0700
commit05f144a0d5c2207a0349348127f996e104ad7404 (patch)
tree2996c5689ed520557f381cf364739eee2f2b87a4 /arch/avr32
parent644473e9c60c1ff4f6351fed637a6e5551e3dce7 (diff)
mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages
Dave Jones' system call fuzz testing tool "trinity" triggered the following bug error with slab debugging enabled ============================================================================= BUG numa_policy (Not tainted): Poison overwritten ----------------------------------------------------------------------------- INFO: 0xffff880146498250-0xffff880146498250. First byte 0x6a instead of 0x6b INFO: Allocated in mpol_new+0xa3/0x140 age=46310 cpu=6 pid=32154 __slab_alloc+0x3d3/0x445 kmem_cache_alloc+0x29d/0x2b0 mpol_new+0xa3/0x140 sys_mbind+0x142/0x620 system_call_fastpath+0x16/0x1b INFO: Freed in __mpol_put+0x27/0x30 age=46268 cpu=6 pid=32154 __slab_free+0x2e/0x1de kmem_cache_free+0x25a/0x260 __mpol_put+0x27/0x30 remove_vma+0x68/0x90 exit_mmap+0x118/0x140 mmput+0x73/0x110 exit_mm+0x108/0x130 do_exit+0x162/0xb90 do_group_exit+0x4f/0xc0 sys_exit_group+0x17/0x20 system_call_fastpath+0x16/0x1b INFO: Slab 0xffffea0005192600 objects=27 used=27 fp=0x (null) flags=0x20000000004080 INFO: Object 0xffff880146498250 @offset=592 fp=0xffff88014649b9d0 This implied a reference counting bug and the problem happened during mbind(). mbind() applies a new memory policy to a range and uses mbind_range() to merge existing VMAs or split them as necessary. In the event of splits, mpol_dup() will allocate a new struct mempolicy and maintain existing reference counts whose rules are documented in Documentation/vm/numa_memory_policy.txt . The problem occurs with shared memory policies. The vm_op->set_policy increments the reference count if necessary and split_vma() and vma_merge() have already handled the existing reference counts. However, policy_vma() screws it up by replacing an existing vma->vm_policy with one that potentially has the wrong reference count leading to a premature free. This patch removes the damage caused by policy_vma(). With this patch applied Dave's trinity tool runs an mbind test for 5 minutes without error. /proc/slabinfo reported that there are no numa_policy or shared_policy_node objects allocated after the test completed and the shared memory region was deleted. Signed-off-by: Mel Gorman <mgorman@suse.de> Cc: Dave Jones <davej@redhat.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Stephen Wilson <wilsons@start.ca> Cc: Christoph Lameter <cl@linux.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: <stable@vger.kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/avr32')
0 files changed, 0 insertions, 0 deletions