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authorAndrea Arcangeli <aarcange@redhat.com>2017-02-23 00:43:55 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-23 01:41:29 +0100
commitcb658a453b9327ce96ce5222c24d162b5b65b564 (patch)
treedc5078cdec1b41f2ff11e0ee693564a9a47e806e /mm/shmem.c
parentuserfaultfd: shmem: avoid a lockup resulting from corrupted page->flags (diff)
downloadlinux-cb658a453b9327ce96ce5222c24d162b5b65b564.tar.xz
linux-cb658a453b9327ce96ce5222c24d162b5b65b564.zip
userfaultfd: shmem: avoid leaking blocks and used blocks in UFFDIO_COPY
If the atomic copy_user fails because of a real dangling userland pointer, we won't go back into the shmem method, so when the method returns it must not leave anything charged up, except the page itself. Link: http://lkml.kernel.org/r/20161216144821.5183-37-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Michael Rapoport <RAPOPORT@il.ibm.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
-rw-r--r--mm/shmem.c23
1 files changed, 13 insertions, 10 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 8d7d80cf8708..9c6d22ff44e2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2214,17 +2214,17 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
pte_t _dst_pte, *dst_pte;
int ret;
- if (!*pagep) {
- ret = -ENOMEM;
- if (shmem_acct_block(info->flags, 1))
- goto out;
- if (sbinfo->max_blocks) {
- if (percpu_counter_compare(&sbinfo->used_blocks,
- sbinfo->max_blocks) >= 0)
- goto out_unacct_blocks;
- percpu_counter_inc(&sbinfo->used_blocks);
- }
+ ret = -ENOMEM;
+ if (shmem_acct_block(info->flags, 1))
+ goto out;
+ if (sbinfo->max_blocks) {
+ if (percpu_counter_compare(&sbinfo->used_blocks,
+ sbinfo->max_blocks) >= 0)
+ goto out_unacct_blocks;
+ percpu_counter_inc(&sbinfo->used_blocks);
+ }
+ if (!*pagep) {
page = shmem_alloc_page(gfp, info, pgoff);
if (!page)
goto out_dec_used_blocks;
@@ -2237,6 +2237,9 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
/* fallback to copy_from_user outside mmap_sem */
if (unlikely(ret)) {
*pagep = page;
+ if (sbinfo->max_blocks)
+ percpu_counter_add(&sbinfo->used_blocks, -1);
+ shmem_unacct_blocks(info->flags, 1);
/* don't free the page */
return -EFAULT;
}