[PATCH] btrfs: ref-verify: free ref cache before clearing mount opt

[PATCH] btrfs: ref-verify: free ref cache before clearing mount opt

[Fedor Pchelkin]

As clearing REF_VERIFY mount option indicates there were some errors in a
ref-verify process, a ref cache is not relevant anymore and should be
freed.

btrfs_free_ref_cache() requires REF_VERIFY option being set so call
it just before clearing the mount option.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: fd708b81d972 ("Btrfs: add a extent ref verify tool")
Reported-by: syzbot+be14ed7728594dc8bd42@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000e5a65c05ee832054@google.com/
Reported-by: syzbot+c563a3c79927971f950f@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/0000000000007fe09705fdc6086c@google.com/
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
---
 fs/btrfs/ref-verify.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/ref-verify.c b/fs/btrfs/ref-verify.c
index 6486f0d7e993..8c4fc98ca9ce 100644
--- a/fs/btrfs/ref-verify.c
+++ b/fs/btrfs/ref-verify.c
@@ -889,8 +889,10 @@ int btrfs_ref_tree_mod(struct btrfs_fs_info *fs_info,
 out_unlock:
 	spin_unlock(&fs_info->ref_verify_lock);
 out:
-	if (ret)
+	if (ret) {
+		btrfs_free_ref_cache(fs_info);
 		btrfs_clear_opt(fs_info->mount_opt, REF_VERIFY);
+	}
 	return ret;
 }
 
@@ -1021,8 +1023,8 @@ int btrfs_build_ref_tree(struct btrfs_fs_info *fs_info)
 		}
 	}
 	if (ret) {
-		btrfs_clear_opt(fs_info->mount_opt, REF_VERIFY);
 		btrfs_free_ref_cache(fs_info);
+		btrfs_clear_opt(fs_info->mount_opt, REF_VERIFY);
 	}
 	btrfs_free_path(path);
 	return ret;
-- 
2.43.0

Re: [PATCH] btrfs: ref-verify: free ref cache before clearing mount opt

[Anand Jain]

Reviewed-by: Anand Jain <anand.jain@oracle.com>

Thx, Anand

Re: [PATCH] btrfs: ref-verify: free ref cache before clearing mount opt

[David Sterba]

On Wed, Jan 03, 2024 at 01:31:27PM +0300, Fedor Pchelkin wrote:
> As clearing REF_VERIFY mount option indicates there were some errors in a
> ref-verify process, a ref cache is not relevant anymore and should be
> freed.
> 
> btrfs_free_ref_cache() requires REF_VERIFY option being set so call
> it just before clearing the mount option.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Fixes: fd708b81d972 ("Btrfs: add a extent ref verify tool")
> Reported-by: syzbot+be14ed7728594dc8bd42@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/lkml/000000000000e5a65c05ee832054@google.com/
> Reported-by: syzbot+c563a3c79927971f950f@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/lkml/0000000000007fe09705fdc6086c@google.com/
> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>

Added to misc-next, thanks.