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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>
This commit is contained in:
Andrea Arcangeli 2017-02-22 15:43:55 -08:00 committed by Linus Torvalds
parent a425d3584e
commit cb658a453b
1 changed files with 13 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
mm/shmem.c
View File

@ -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;
}