linux-kernel - [PATCH v2] btrfs: qgroup: don't use extent changeset when not needed

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Message-Id: <20240828161411.534042-1-pchelkin@ispras.ru>
Date: Wed, 28 Aug 2024 19:14:11 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Qu Wenruo <quwenruo.btrfs@....com>,
	David Sterba <dsterba@...e.com>
Cc: Fedor Pchelkin <pchelkin@...ras.ru>,
	Chris Mason <clm@...com>,
	Josef Bacik <josef@...icpanda.com>,
	Boris Burkov <boris@....io>,
	linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	syzbot+81670362c283f3dd889c@...kaller.appspotmail.com,
	stable@...r.kernel.org
Subject: [PATCH v2] btrfs: qgroup: don't use extent changeset when not needed

The local extent changeset is passed to clear_record_extent_bits() where
it may have some additional memory dynamically allocated for ulist. When
qgroup is disabled, the memory is leaked because in this case the
changeset is not released upon __btrfs_qgroup_release_data() return.

Since the recorded contents of the changeset are not used thereafter, just
don't pass it.

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

Reported-by: syzbot+81670362c283f3dd889c@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000aa8c0c060ade165e@google.com
Fixes: af0e2aab3b70 ("btrfs: qgroup: flush reservations during quota disable")
Cc: stable@...r.kernel.org # 6.10+
Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
---
v2: rework the fix as Qu Wenruo suggested - just don't pass unneeded
    changeset. Update the commit title and description accordingly.

 fs/btrfs/qgroup.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 5d57a285d59b..f6118c5f3c9f 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -4344,10 +4344,9 @@ static int __btrfs_qgroup_release_data(struct btrfs_inode *inode,
 	int ret;
 
 	if (btrfs_qgroup_mode(inode->root->fs_info) == BTRFS_QGROUP_MODE_DISABLED) {
-		extent_changeset_init(&changeset);
 		return clear_record_extent_bits(&inode->io_tree, start,
 						start + len - 1,
-						EXTENT_QGROUP_RESERVED, &changeset);
+						EXTENT_QGROUP_RESERVED, NULL);
 	}
 
 	/* In release case, we shouldn't have @reserved */
-- 
2.39.2