From 87dcf0c61985e4e6b44d9a95de54373438eb31cd Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Thu, 14 Mar 2019 09:52:35 +0200 Subject: [PATCH] btrfs: Correctly free extent buffer in case btree_read_extent_buffer_pages fails commit 537f38f019fa0b762dbb4c0fc95d7fcce9db8e2d upstream. If a an eb fails to be read for whatever reason - it's corrupted on disk and parent transid/key validations fail or IO for eb pages fail then this buffer must be removed from the buffer cache. Currently the code calls free_extent_buffer if an error occurs. Unfortunately this doesn't achieve the desired behavior since btrfs_find_create_tree_block returns with eb->refs == 2. On the other hand free_extent_buffer will only decrement the refs once leaving it added to the buffer cache radix tree. This enables later code to look up the buffer from the cache and utilize it potentially leading to a crash. The correct way to free the buffer is call free_extent_buffer_stale. This function will correctly call atomic_dec explicitly for the buffer and subsequently call release_extent_buffer which will decrement the final reference thus correctly remove the invalid buffer from buffer cache. This change affects only newly allocated buffers since they have eb->refs == 2. Link: https://bugzilla.kernel.org/show_bug.cgi?id=202755 Reported-by: Jungyeon CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/disk-io.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index d67dbbd9e6ed..b2dc613ebed2 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -995,13 +995,18 @@ void readahead_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr) { struct extent_buffer *buf = NULL; struct inode *btree_inode = fs_info->btree_inode; + int ret; buf = btrfs_find_create_tree_block(fs_info, bytenr); if (IS_ERR(buf)) return; - read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree, - buf, WAIT_NONE, 0); - free_extent_buffer(buf); + + ret = read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree, buf, + WAIT_NONE, 0); + if (ret < 0) + free_extent_buffer_stale(buf); + else + free_extent_buffer(buf); } int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr, @@ -1021,12 +1026,12 @@ int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr, ret = read_extent_buffer_pages(io_tree, buf, WAIT_PAGE_LOCK, mirror_num); if (ret) { - free_extent_buffer(buf); + free_extent_buffer_stale(buf); return ret; } if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) { - free_extent_buffer(buf); + free_extent_buffer_stale(buf); return -EIO; } else if (extent_buffer_uptodate(buf)) { *eb = buf; @@ -1080,7 +1085,7 @@ struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr, ret = btree_read_extent_buffer_pages(fs_info, buf, parent_transid, level, first_key); if (ret) { - free_extent_buffer(buf); + free_extent_buffer_stale(buf); return ERR_PTR(ret); } return buf; -- GitLab