Commit cb658a45 authored Feb 22, 2017 by Andrea Arcangeli Committed by Linus Torvalds Feb 22, 2017

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>

parent a425d358

mm/shmem.c

+13 −10

Original line number	Diff line number	Diff line
		@@ -2214,7 +2214,6 @@ 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;
		@@ -2225,6 +2224,7 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm,
		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;
		}