[PATCH] btrfs: fix uninitialized parent in insert_state

[PATCH] btrfs: fix uninitialized parent in insert_state

[Josef Bacik]

I don't know how this isn't caught when we build this in the kernel, but
while sync'ing extent-io-tree.c into btrfs-progs I got an error because
parent could potentially be uninitialized when we link in a new node,
specifically when the extent_io_tree is empty.  This means we could have
garbage in the parent color.  I don't know what the ramifications are of
that, but it's probably not great, so fix this by init'ing parent to
NULL.  I spot checked all of our other usages in btrfs and we appear to
be doing the correct thing everywhere else.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/extent-io-tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/extent-io-tree.c b/fs/btrfs/extent-io-tree.c
index 285b0ff6e953..25215667a3de 100644
--- a/fs/btrfs/extent-io-tree.c
+++ b/fs/btrfs/extent-io-tree.c
@@ -395,7 +395,7 @@ static int insert_state(struct extent_io_tree *tree,
 			u32 bits, struct extent_changeset *changeset)
 {
 	struct rb_node **node;
-	struct rb_node *parent;
+	struct rb_node *parent = NULL;
 	const u64 end = state->end;
 
 	set_state_bits(tree, state, bits, changeset);
-- 
2.26.3

Re: [PATCH] btrfs: fix uninitialized parent in insert_state

[David Sterba]

On Fri, Nov 18, 2022 at 03:06:09PM -0500, Josef Bacik wrote:
> I don't know how this isn't caught when we build this in the kernel, but
> while sync'ing extent-io-tree.c into btrfs-progs I got an error because
> parent could potentially be uninitialized when we link in a new node,
> specifically when the extent_io_tree is empty.  This means we could have
> garbage in the parent color.  I don't know what the ramifications are of
> that, but it's probably not great, so fix this by init'ing parent to
> NULL.  I spot checked all of our other usages in btrfs and we appear to
> be doing the correct thing everywhere else.
> 
> Signed-off-by: Josef Bacik <josef@toxicpanda.com>

Added to misc-next, thanks. The initialization got lost during the
conversion in c7e118cf98c7 ("btrfs: open code rbtree search in
insert_state").