kernel.git/mm/mempolicy.c, branch linux-3.6.y

tmpfs: fix shared mempolicy leak

2012-12-17T17:26:50Z

commit 18a2f371f5edf41810f6469cb9be39931ef9deb9 upstream. This fixes a regression in 3.7-rc, which has since gone into stable. Commit 00442ad04a5e ("mempolicy: fix a memory corruption by refcount imbalance in alloc_pages_vma()") changed get_vma_policy() to raise the refcount on a shmem shared mempolicy; whereas shmem_alloc_page() went on expecting alloc_page_vma() to drop the refcount it had acquired. This deserves a rework: but for now fix the leak in shmem_alloc_page(). Hugh: shmem_swapin() did not need a fix, but surely it's clearer to use the same refcounting there as in shmem_alloc_page(), delete its onstack mempolicy, and the strange mpol_cond_copy() and __mpol_cond_copy() - those were invented to let swapin_readahead() make an unknown number of calls to alloc_pages_vma() with one mempolicy; but since 00442ad04a5e, alloc_pages_vma() has kept refcount in balance, so now no problem. Reported-and-tested-by: Tommi Rantala Signed-off-by: Mel Gorman Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mempolicy: fix a memory corruption by refcount imbalance in alloc_pages_vma()

2012-10-12T20:50:32Z

commit 00442ad04a5eac08a98255697c510e708f6082e2 upstream. Commit cc9a6c877661 ("cpuset: mm: reduce large amounts of memory barrier related damage v3") introduced a potential memory corruption. shmem_alloc_page() uses a pseudo vma and it has one significant unique combination, vma->vm_ops=NULL and vma->policy->flags & MPOL_F_SHARED. get_vma_policy() does NOT increase a policy ref when vma->vm_ops=NULL and mpol_cond_put() DOES decrease a policy ref when a policy has MPOL_F_SHARED. Therefore, when a cpuset update race occurs, alloc_pages_vma() falls in 'goto retry_cpuset' path, decrements the reference count and frees the policy prematurely. Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Christoph Lameter Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mempolicy: fix refcount leak in mpol_set_shared_policy()

2012-10-12T20:50:32Z

commit 63f74ca21f1fad36d075e063f06dcc6d39fe86b2 upstream. When shared_policy_replace() fails to allocate new->policy is not freed correctly by mpol_set_shared_policy(). The problem is that shared mempolicy code directly call kmem_cache_free() in multiple places where it is easy to make a mistake. This patch creates an sp_free wrapper function and uses it. The bug was introduced pre-git age (IOW, before 2.6.12-rc2). [mgorman@suse.de: Editted changelog] Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Reviewed-by: Christoph Lameter Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mempolicy: fix a race in shared_policy_replace()

2012-10-12T20:50:32Z

commit b22d127a39ddd10d93deee3d96e643657ad53a49 upstream. shared_policy_replace() use of sp_alloc() is unsafe. 1) sp_node cannot be dereferenced if sp->lock is not held and 2) another thread can modify sp_node between spin_unlock for allocating a new sp node and next spin_lock. The bug was introduced before 2.6.12-rc2. Kosaki's original patch for this problem was to allocate an sp node and policy within shared_policy_replace and initialise it when the lock is reacquired. I was not keen on this approach because it partially duplicates sp_alloc(). As the paths were sp->lock is taken are not that performance critical this patch converts sp->lock to sp->mutex so it can sleep when calling sp_alloc(). [kosaki.motohiro@jp.fujitsu.com: Original patch] Signed-off-by: Mel Gorman Acked-by: KOSAKI Motohiro Reviewed-by: Christoph Lameter Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mempolicy: remove mempolicy sharing

2012-10-12T20:50:32Z

commit 869833f2c5c6e4dd09a5378cfc665ffb4615e5d2 upstream. 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 The problem is that the structure is being prematurely freed due to a reference count imbalance. In the following case mbind(addr, len) should replace the memory policies of both vma1 and vma2 and thus they will become to share the same mempolicy and the new mempolicy will have the MPOL_F_SHARED flag. +-------------------+-------------------+ | vma1 | vma2(shmem) | +-------------------+-------------------+ | | addr addr+len alloc_pages_vma() uses get_vma_policy() and mpol_cond_put() pair for maintaining the mempolicy reference count. The current rule is that get_vma_policy() only increments refcount for shmem VMA and mpol_conf_put() only decrements refcount if the policy has MPOL_F_SHARED. In above case, vma1 is not shmem vma and vma->policy has MPOL_F_SHARED! The reference count will be decreased even though was not increased whenever alloc_page_vma() is called. This has been broken since commit [52cd3b07: mempolicy: rework mempolicy Reference Counting] in 2008. There is another serious bug with the sharing of memory policies. Currently, mempolicy rebind logic (it is called from cpuset rebinding) ignores a refcount of mempolicy and override it forcibly. Thus, any mempolicy sharing may cause mempolicy corruption. The bug was introduced by commit [68860ec1: cpusets: automatic numa mempolicy rebinding]. Ideally, the shared policy handling would be rewritten to either properly handle COW of the policy structures or at least reference count MPOL_F_SHARED based exclusively on information within the policy. However, this patch takes the easier approach of disabling any policy sharing between VMAs. Each new range allocated with sp_alloc will allocate a new policy, set the reference count to 1 and drop the reference count of the old policy. This increases the memory footprint but is not expected to be a major problem as mbind() is unlikely to be used for fine-grained ranges. It is also inefficient because it means we allocate a new policy even in cases where mbind_range() could use the new_policy passed to it. However, it is more straight-forward and the change should be invisible to the user. [mgorman@suse.de: Edited changelog] Reported-by: Dave Jones , Cc: Christoph Lameter , Reviewed-by: Christoph Lameter Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

revert "mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages"

2012-10-12T20:50:31Z

commit 8d34694c1abf29df1f3c7317936b7e3e2e308d9b upstream. Commit 05f144a0d5c2 ("mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages") removed vma->vm_policy updates code but it is the purpose of mbind_range(). Now, mbind_range() is virtually a no-op and while it does not allow memory corruption it is not the right fix. This patch is a revert. [mgorman@suse.de: Edited changelog] Signed-off-by: KOSAKI Motohiro Signed-off-by: Mel Gorman Cc: Christoph Lameter Cc: Josh Boyer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

Remove user-triggerable BUG from mpol_to_str

2012-09-06T16:37:58Z

Trivially triggerable, found by trinity: kernel BUG at mm/mempolicy.c:2546! Process trinity-child2 (pid: 23988, threadinfo ffff88010197e000, task ffff88007821a670) Call Trace: show_numa_map+0xd5/0x450 show_pid_numa_map+0x13/0x20 traverse+0xf2/0x230 seq_read+0x34b/0x3e0 vfs_read+0xac/0x180 sys_pread64+0xa2/0xc0 system_call_fastpath+0x1a/0x1f RIP: mpol_to_str+0x156/0x360 Cc: stable@vger.kernel.org Signed-off-by: Dave Jones Signed-off-by: Linus Torvalds

Merge branch 'slab/next' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux

2012-07-30T18:32:24Z

Pull SLAB changes from Pekka Enberg: "Most of the changes included are from Christoph Lameter's "common slab" patch series that unifies common parts of SLUB, SLAB, and SLOB allocators. The unification is needed for Glauber Costa's "kmem memcg" work that will hopefully appear for v3.7. The rest of the changes are fixes and speedups by various people." * 'slab/next' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/linux: (32 commits) mm: Fix build warning in kmem_cache_create() slob: Fix early boot kernel crash mm, slub: ensure irqs are enabled for kmemcheck mm, sl[aou]b: Move kmem_cache_create mutex handling to common code mm, sl[aou]b: Use a common mutex definition mm, sl[aou]b: Common definition for boot state of the slab allocators mm, sl[aou]b: Extract common code for kmem_cache_create() slub: remove invalid reference to list iterator variable mm: Fix signal SIGFPE in slabinfo.c. slab: move FULL state transition to an initcall slab: Fix a typo in commit 8c138b "slab: Get rid of obj_size macro" mm, slab: Build fix for recent kmem_cache changes slab: rename gfpflags to allocflags slub: refactoring unfreeze_partials() slub: use __cmpxchg_double_slab() at interrupt disabled place slab/mempolicy: always use local policy from interrupt context slab: Get rid of obj_size macro mm, sl[aou]b: Extract common fields from struct kmem_cache slab: Remove some accessors slab: Use page struct fields instead of casting ...

mm, mempolicy: fix mbind() to do synchronous migration

2012-06-21T05:10:42Z

If the range passed to mbind() is not allocated on nodes set in the nodemask, it migrates the pages to respect the constraint. The final formal of migrate_pages() is a mode of type enum migrate_mode, not a boolean. do_mbind() is currently passing "true" which is the equivalent of MIGRATE_SYNC_LIGHT. This should instead be MIGRATE_SYNC for synchronous page migration. Signed-off-by: David Rientjes Signed-off-by: Linus Torvalds

slab/mempolicy: always use local policy from interrupt context

2012-06-20T07:01:04Z

slab_node() could access current->mempolicy from interrupt context. However there's a race condition during exit where the mempolicy is first freed and then the pointer zeroed. Using this from interrupts seems bogus anyways. The interrupt will interrupt a random process and therefore get a random mempolicy. Many times, this will be idle's, which noone can change. Just disable this here and always use local for slab from interrupts. I also cleaned up the callers of slab_node a bit which always passed the same argument. I believe the original mempolicy code did that in fact, so it's likely a regression. v2: send version with correct logic v3: simplify. fix typo. Reported-by: Arun Sharma Cc: penberg@kernel.org Cc: cl@linux.com Signed-off-by: Andi Kleen [tdmackey@twitter.com: Rework control flow based on feedback from cl@linux.com, fix logic, and cleanup current task_struct reference] Acked-by: David Rientjes Acked-by: Christoph Lameter Acked-by: KOSAKI Motohiro Signed-off-by: David Mackey Signed-off-by: Pekka Enberg