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btrfs: use refcount_inc_not_zero in kill_all_nodes

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commit baf320b9d531f1cfbf64c60dd155ff80a58b3796 upstream.

We hit the following warning while running down a different problem

[ 6197.175850] ------------[ cut here ]------------
[ 6197.185082] refcount_t: underflow; use-after-free.
[ 6197.194704] WARNING: CPU: 47 PID: 966 at lib/refcount.c:190 refcount_sub_and_test_checked+0x53/0x60
[ 6197.521792] Call Trace:
[ 6197.526687]  __btrfs_release_delayed_node+0x76/0x1c0
[ 6197.536615]  btrfs_kill_all_delayed_nodes+0xec/0x130
[ 6197.546532]  ? __btrfs_btree_balance_dirty+0x60/0x60
[ 6197.556482]  btrfs_clean_one_deleted_snapshot+0x71/0xd0
[ 6197.566910]  cleaner_kthread+0xfa/0x120
[ 6197.574573]  kthread+0x111/0x130
[ 6197.581022]  ? kthread_create_on_node+0x60/0x60
[ 6197.590086]  ret_from_fork+0x1f/0x30
[ 6197.597228] ---[ end trace 424bb7ae00509f56 ]---

This is because the free side drops the ref without the lock, and then
takes the lock if our refcount is 0.  So you can have nodes on the tree
that have a refcount of 0.  Fix this by zero'ing out that element in our
temporary array so we don't try to kill it again.

CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ add comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josef Bacik 2019-09-26 08:29:32 -04:00 committed by Greg Kroah-Hartman
parent 6e3b9068b8
commit eda96b244d
1 changed files with 10 additions and 3 deletions
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13
fs/btrfs/delayed-inode.c
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@ -1939,12 +1939,19 @@ void btrfs_kill_all_delayed_nodes(struct btrfs_root *root)
}
inode_id = delayed_nodes[n - 1]->inode_id + 1;
for (i = 0; i < n; i++)
refcount_inc(&delayed_nodes[i]->refs);
for (i = 0; i < n; i++) {
/*
* Don't increase refs in case the node is dead and
* about to be removed from the tree in the loop below
*/
if (!refcount_inc_not_zero(&delayed_nodes[i]->refs))
delayed_nodes[i] = NULL;
}
spin_unlock(&root->inode_lock);
for (i = 0; i < n; i++) {
if (!delayed_nodes[i])
continue;
__btrfs_kill_delayed_node(delayed_nodes[i]);
btrfs_release_delayed_node(delayed_nodes[i]);
}