[BUG]
v4.14 btrfs-progs can't pass new self test image with large tree reloc
trees.
It will fail with later "shared_block_ref_only.raw.xz" test image with
NULL pointer access.
[CAUSE]
For image with higher (level >= 2) tree reloc tree, for function
need_check() its ulist will be empty as tree reloc tree won't be
accounted in btrfs_find_all_roots().
Then accessing ulist->roots with rb_first() will return NULL pointer.
[FIX]
For need_check() function, if @roots is empty, meaning it's a tree reloc
tree, always check them.
Although this can be slow, but at least it's safe that we won't skip any
possible wrong tree block.
Fixes: 5e2dc770471b ("btrfs-progs: check: skip shared node or leaf check for low_memory mode")
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
cmds-check.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/cmds-check.c b/cmds-check.c
index 644ee084cb8e..03ff89a4221c 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -2149,7 +2149,12 @@ static int need_check(struct btrfs_root *root, struct ulist *roots)
struct rb_node *node;
struct ulist_node *u;
- if (roots->nnodes == 1)
+ /*
+ * @roots can be empty if it belongs to tree reloc tree
+ * In that case, we should always check the leaf, as we can't use
+ * the tree owner to ensure some other root will check it.
+ */
+ if (roots->nnodes == 1 || roots->nnodes == 0)
return 1;
node = rb_first(&roots->root);
--
2.15.0
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