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btrfs: fix root ref counts in error handling in btrfs_get_root_ref

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In btrfs_get_root_ref(), when btrfs_insert_fs_root() fails,
btrfs_put_root() can happen for two reasons:

- the root already exists in the tree, in that case it returns the
  reference obtained in btrfs_lookup_fs_root()

- another error so the cleanup is done in the fail label

Calling btrfs_put_root() unconditionally would lead to double decrement
of the root reference possibly freeing it in the second case.

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Fixes: bc44d7c4b2 ("btrfs: push btrfs_grab_fs_root into btrfs_get_fs_root")
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Jia-Ju Bai 2022-03-24 06:44:54 -07:00 committed by David Sterba
parent 760e69c4c2
commit 168a2f776b
1 changed files with 3 additions and 2 deletions
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3
fs/btrfs/disk-io.c
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@ -1849,9 +1849,10 @@ again:
ret = btrfs_insert_fs_root(fs_info, root);
if (ret) {
if (ret == -EEXIST) {
btrfs_put_root(root);
if (ret == -EEXIST)
goto again;
}
goto fail;
}
return root;