From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f42.google.com ([209.85.214.42]:37699 "EHLO mail-it0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138AbdFBIVg (ORCPT ); Fri, 2 Jun 2017 04:21:36 -0400 Received: by mail-it0-f42.google.com with SMTP id m47so10042866iti.0 for ; Fri, 02 Jun 2017 01:21:35 -0700 (PDT) From: Omar Sandoval To: linux-btrfs@vger.kernel.org, Chris Mason , Josef Bacik Cc: kernel-team@fb.com, stable@vger.kernel.org Subject: [PATCH] Btrfs: fix delalloc accounting leak caused by u32 overflow Date: Fri, 2 Jun 2017 01:20:01 -0700 Message-Id: <4d268ba97ee6511e4a8c42d39c64316d20eed9d0.1496391402.git.osandov@fb.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: From: Omar Sandoval btrfs_calc_trans_metadata_size() does an unsigned 32-bit multiplication, which can overflow if num_items >= 4 GB / (nodesize * BTRFS_MAX_LEVEL * 2). For a nodesize of 16kB, this overflow happens at 16k items. Usually, num_items is a small constant passed to btrfs_start_transaction(), but we also use btrfs_calc_trans_metadata_size() for metadata reservations for extent items in btrfs_delalloc_{reserve,release}_metadata(). In drop_outstanding_extents(), num_items is calculated as inode->reserved_extents - inode->outstanding_extents. The difference between these two counters is usually small, but if many delalloc extents are reserved and then the outstanding extents are merged in btrfs_merge_extent_hook(), the difference can become large enough to overflow in btrfs_calc_trans_metadata_size(). The overflow manifests itself as a leak of a multiple of 4 GB in delalloc_block_rsv and the metadata bytes_may_use counter. This in turn can cause early ENOSPC errors. Additionally, these WARN_ONs in extent-tree.c will be hit when unmounting: WARN_ON(fs_info->delalloc_block_rsv.size > 0); WARN_ON(fs_info->delalloc_block_rsv.reserved > 0); WARN_ON(space_info->bytes_pinned > 0 || space_info->bytes_reserved > 0 || space_info->bytes_may_use > 0); Fix it by casting nodesize to a u64 so that btrfs_calc_trans_metadata_size() does a full 64-bit multiplication. While we're here, do the same in btrfs_calc_trunc_metadata_size(); this can't overflow with any existing uses, but it's better to be safe here than have another hard-to-debug problem later on. Cc: stable@vger.kernel.org Signed-off-by: Omar Sandoval --- fs/btrfs/ctree.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 643c70d2b2e6..4f8f75d9e839 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -2563,7 +2563,7 @@ u64 btrfs_csum_bytes_to_leaves(struct btrfs_fs_info *fs_info, u64 csum_bytes); static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_fs_info *fs_info, unsigned num_items) { - return fs_info->nodesize * BTRFS_MAX_LEVEL * 2 * num_items; + return (u64)fs_info->nodesize * BTRFS_MAX_LEVEL * 2 * num_items; } /* @@ -2573,7 +2573,7 @@ static inline u64 btrfs_calc_trans_metadata_size(struct btrfs_fs_info *fs_info, static inline u64 btrfs_calc_trunc_metadata_size(struct btrfs_fs_info *fs_info, unsigned num_items) { - return fs_info->nodesize * BTRFS_MAX_LEVEL * num_items; + return (u64)fs_info->nodesize * BTRFS_MAX_LEVEL * num_items; } int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans, -- 2.13.0