From 230ed397435e85b54f055c524fcb267ae2ce3bc4 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Mon, 6 Jul 2020 09:14:12 -0400 Subject: [PATCH] btrfs: fix double put of block group with nocow 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 Signed-off-by: Josef Bacik Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/inode.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index cfa863d2d97c0..11f81a1483504 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1690,12 +1690,8 @@ 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; } @@ -1711,9 +1707,6 @@ 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; } -- 2.30.2