[PATCH 4.14 27/65] btrfs: fix memory leak in qgroup accounting

Greg Kroah-Hartman
2020-01-22T09:38:43Z

From: Johannes Thumshirn <johannes.thumshirn@wdc.com>

commit 26ef8493e1ab771cb01d27defca2fa1315dc3980 upstream.

When running xfstests on the current btrfs I get the following splat from
kmemleak:

unreferenced object 0xffff88821b2404e0 (size 32):
comm "kworker/u4:7", pid 26663, jiffies 4295283698 (age 8.776s)
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 10 ff fd 26 82 88 ff ff ...........&....
10 ff fd 26 82 88 ff ff 20 ff fd 26 82 88 ff ff ...&.... ..&....
backtrace:
[<00000000f94fd43f>] ulist_alloc+0x25/0x60 [btrfs]
[<00000000fd023d99>] btrfs_find_all_roots_safe+0x41/0x100 [btrfs]
[<000000008f17bd32>] btrfs_find_all_roots+0x52/0x70 [btrfs]
[<00000000b7660afb>] btrfs_qgroup_rescan_worker+0x343/0x680 [btrfs]
[<0000000058e66778>] btrfs_work_helper+0xac/0x1e0 [btrfs]
[<00000000f0188930>] process_one_work+0x1cf/0x350
[<00000000af5f2f8e>] worker_thread+0x28/0x3c0
[<00000000b55a1add>] kthread+0x109/0x120
[<00000000f88cbd17>] ret_from_fork+0x35/0x40

This corresponds to:

(gdb) l *(btrfs_find_all_roots_safe+0x41)
0x8d7e1 is in btrfs_find_all_roots_safe (fs/btrfs/backref.c:1413).
1408
1409 tmp = ulist_alloc(GFP_NOFS);
1410 if (!tmp)
1411 return -ENOMEM;
1412 *roots = ulist_alloc(GFP_NOFS);
1413 if (!*roots) {
1414 ulist_free(tmp);
1415 return -ENOMEM;
1416 }
1417

Following the lifetime of the allocated 'roots' ulist, it gets freed
again in btrfs_qgroup_account_extent().

But this does not happen if the function is called with the
'BTRFS_FS_QUOTA_ENABLED' flag cleared, then btrfs_qgroup_account_extent()
does a short leave and directly returns.

Instead of directly returning we should jump to the 'out_free' in order to
free all resources as expected.

CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/qgroup.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -1928,8 +1928,12 @@ btrfs_qgroup_account_extent(struct btrfs
u64 nr_old_roots = 0;
int ret = 0;

+ /*
+ * If quotas get disabled meanwhile, the resouces need to be freed and
+ * we can't just exit here.
+ */
if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
- return 0;
+ goto out_free;

if (new_roots) {
if (!maybe_fs_roots(new_roots))