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btrfs: validate root::reloc_root after recording root in trans 

If we fail to setup a root->reloc_root in a different thread that path
will error out, however it still leaves root->reloc_root NULL but would
still appear set up in the transaction.  Subsequent calls to
btrfs_record_root_in_transaction would succeed without attempting to
create the reloc root, as the transid has already been updated.

Handle this case by making sure we have a root->reloc_root set after a
btrfs_record_root_in_transaction call so we don't end up dereferencing a
NULL pointer.

Reported-by: Zygo Blaxell <ce3g8jdj@umail.furryterror.org>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2021-03-12 15:25:15 -05:00 committed by David Sterba
parent 84c50ba521
commit 39200e5908
1 changed files with 15 additions and 0 deletions
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15
fs/btrfs/relocation.c
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@ -2082,6 +2082,13 @@ struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
return ERR_PTR(ret);
root = root->reloc_root;
/*
* We could have raced with another thread which failed, so
* root->reloc_root may not be set, return ENOENT in this case.
*/
if (!root)
return ERR_PTR(-ENOENT);
if (next->new_bytenr != root->node->start) {
/*
* We just created the reloc root, so we shouldn't have
@ -2579,6 +2586,14 @@ static int relocate_tree_block(struct btrfs_trans_handle *trans,
ret = btrfs_record_root_in_trans(trans, root);
if (ret)
goto out;
/*
* Another thread could have failed, need to check if we
* have reloc_root actually set.
*/
if (!root->reloc_root) {
ret = -ENOENT;
goto out;
}
root = root->reloc_root;
node->new_bytenr = root->node->start;
btrfs_put_root(node->root);