From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/shmem.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) diff -puN mm/shmem.c~userfaultfd-shmem-avoid-leaking-blocks-and-used-blocks-in-uffdio_copy mm/shmem.c --- a/mm/shmem.c~userfaultfd-shmem-avoid-leaking-blocks-and-used-blocks-in-uffdio_copy +++ a/mm/shmem.c @@ -2214,17 +2214,17 @@ int shmem_mcopy_atomic_pte(struct mm_str 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_str /* 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; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
