From 18a2f371f5edf41810f6469cb9be39931ef9deb9 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Wed, 5 Dec 2012 14:01:41 -0800 Subject: tmpfs: fix shared mempolicy leak 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 Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds --- mm/shmem.c | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 89341b658bd0..50c5b8f3a359 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo) static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, struct shmem_inode_info *info, pgoff_t index) { - struct mempolicy mpol, *spol; struct vm_area_struct pvma; - - spol = mpol_cond_copy(&mpol, - mpol_shared_policy_lookup(&info->policy, index)); + struct page *page; /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; /* Bias interleave by inode number to distribute better across nodes */ pvma.vm_pgoff = index + info->vfs_inode.i_ino; pvma.vm_ops = NULL; - pvma.vm_policy = spol; - return swapin_readahead(swap, gfp, &pvma, 0); + pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); + + page = swapin_readahead(swap, gfp, &pvma, 0); + + /* Drop reference taken by mpol_shared_policy_lookup() */ + mpol_cond_put(pvma.vm_policy); + + return page; } static struct page *shmem_alloc_page(gfp_t gfp, struct shmem_inode_info *info, pgoff_t index) { struct vm_area_struct pvma; + struct page *page; /* Create a pseudo vma that just contains the policy */ pvma.vm_start = 0; @@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp_t gfp, pvma.vm_ops = NULL; pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); - /* - * alloc_page_vma() will drop the shared policy reference - */ - return alloc_page_vma(gfp, &pvma, 0); + page = alloc_page_vma(gfp, &pvma, 0); + + /* Drop reference taken by mpol_shared_policy_lookup() */ + mpol_cond_put(pvma.vm_policy); + + return page; } #else /* !CONFIG_NUMA */ #ifdef CONFIG_TMPFS -- cgit v1.2.3