1. in btrfs_find_all_roots
This method uses a ulist to solve the recursion. The local variable
node is used in combination with ulist_next to iterate through the
list. Calls to find_parent_nodes fill up this list. The problem is,
adding new nodes to the ulist may cause the ulist->nodes pointer to
change in case the ulist needs to realloc the buffer. The call to
ulist_next may use a wrong prev pointer in that case, resulting in
undefined behaviour. It is changed now to not use ulist_next.
2. in __iterate_extent_inodes
the first while loop calls btrfs_find_all_roots, which then allocates
a new ulist for the roots. In case the first while loops loops more
then once, we leak the previous ulist as it is not freed.
Point 1 was also causing missed backrefs because the iteration stopped
too early.
Signed-off-by: Alexander Block <ablock84@xxxxxxxxxxxxxx>
---
fs/btrfs/backref.c | 20 ++++++++++++++------
1 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index f28ecba..b08cf93 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -791,6 +791,7 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
struct ulist *tmp;
struct ulist_node *node = NULL;
int ret;
+ int cur;
tmp = ulist_alloc(GFP_NOFS);
if (!tmp)
@@ -801,7 +802,14 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
return -ENOMEM;
}
- while (1) {
+ cur = 0;
+ ulist_add(tmp, bytenr, 0, GFP_NOFS);
+
+ while (cur < tmp->nnodes) {
+ node = &tmp->nodes[cur++];
+ bytenr = node->val;
+
+ /* this will add new nodes to the tmp ulist */
ret = find_parent_nodes(trans, fs_info, bytenr, seq,
tmp, *roots);
if (ret < 0 && ret != -ENOENT) {
@@ -809,10 +817,6 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
ulist_free(*roots);
return ret;
}
- node = ulist_next(tmp, node);
- if (!node)
- break;
- bytenr = node->val;
}
ulist_free(tmp);
@@ -1231,10 +1235,14 @@ static int __iterate_extent_inodes(struct btrfs_fs_info *fs_info,
match_with_offset,
iterate, ctx);
}
+ if (roots)
+ ulist_free(roots);
+ roots = NULL;
}
ulist_free(refs);
- ulist_free(roots);
+ if (roots)
+ ulist_free(roots);
out:
if (!search_commit_root) {
btrfs_put_delayed_seq(delayed_refs, &seq_elem);
--
1.7.3.4
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