From: Josef Bacik josef@toxicpanda.com
commit 230ed397435e85b54f055c524fcb267ae2ce3bc4 upstream.
While debugging a patch that I wrote I was hitting use-after-free panics when accessing block groups on unmount. This turned out to be because in the nocow case if we bail out of doing the nocow for whatever reason we need to call btrfs_dec_nocow_writers() if we called the inc. This puts our block group, but a few error cases does
if (nocow) { btrfs_dec_nocow_writers(); goto error; }
unfortunately, error is
error: if (nocow) btrfs_dec_nocow_writers();
so we get a double put on our block group. Fix this by dropping the error cases calling of btrfs_dec_nocow_writers(), as it's handled at the error label now.
Fixes: 762bf09893b4 ("btrfs: improve error handling in run_delalloc_nocow") CC: stable@vger.kernel.org # 5.4+ Reviewed-by: Filipe Manana fdmanana@suse.com Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/btrfs/inode.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)
--- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1657,12 +1657,8 @@ out_check: ret = fallback_to_cow(inode, locked_page, cow_start, found_key.offset - 1, page_started, nr_written); - if (ret) { - if (nocow) - btrfs_dec_nocow_writers(fs_info, - disk_bytenr); + if (ret) goto error; - } cow_start = (u64)-1; }
@@ -1678,9 +1674,6 @@ out_check: ram_bytes, BTRFS_COMPRESS_NONE, BTRFS_ORDERED_PREALLOC); if (IS_ERR(em)) { - if (nocow) - btrfs_dec_nocow_writers(fs_info, - disk_bytenr); ret = PTR_ERR(em); goto error; }