linux-kernel - [PATCH 5.4 08/57] btrfs: fix transaction leak in btrfs_recover

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Date:   Mon,  4 May 2020 19:57:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>, David Sterba <dsterba@...e.com>
Subject: [PATCH 5.4 08/57] btrfs: fix transaction leak in btrfs_recover_relocation

From: Xiyu Yang <xiyuyang19@...an.edu.cn>

commit 1402d17dfd9657be0da8458b2079d03c2d61c86a upstream.

btrfs_recover_relocation() invokes btrfs_join_transaction(), which joins
a btrfs_trans_handle object into transactions and returns a reference of
it with increased refcount to "trans".

When btrfs_recover_relocation() returns, "trans" becomes invalid, so the
refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
btrfs_recover_relocation(). When read_fs_root() failed, the refcnt
increased by btrfs_join_transaction() is not decreased, causing a refcnt
leak.

Fix this issue by calling btrfs_end_transaction() on this error path
when read_fs_root() failed.

Fixes: 79787eaab461 ("btrfs: replace many BUG_ONs with proper error handling")
CC: stable@...r.kernel.org # 4.4+
Reviewed-by: Filipe Manana <fdmanana@...e.com>
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/relocation.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4605,6 +4605,7 @@ int btrfs_recover_relocation(struct btrf
 		if (IS_ERR(fs_root)) {
 			err = PTR_ERR(fs_root);
 			list_add_tail(&reloc_root->root_list, &reloc_roots);
+			btrfs_end_transaction(trans);
 			goto out_unset;
 		}