在 2025/2/24 18:29, Ma Ke 写道:
btrfs_next_old_leaf() doesn't check if the target root is NULL or not, resulting the null-ptr-deref. Add sanity check for btrfs root before using it in btrfs_next_old_leaf().
Please provide a real world call trace when this is triggered.
There is a prerequisite, the extent tree can only be NULL if rescue=ibadroots is provided and the extent root is corrupted.
And "rescue=" mount options can only be specified for a fully read-only fs (no internal log replay or any other thing to write even a bit into the fs).
Previously read-only scrub can still be triggered on such fs, but 6aecd91a5c5b ("btrfs: avoid NULL pointer dereference if no valid extent tree") fixed that.
And if you hit such a case in real world, please provide the call trace so that we know we're not missing some critical situations that extent tree is accessed for read-only operations.
Thanks, Qu
Found by code review.
Cc: stable@vger.kernel.org Fixes: d96b34248c2f ("btrfs: make send work with concurrent block group relocation") Signed-off-by: Ma Ke make24@iscas.ac.cn
fs/btrfs/ctree.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 4e2e1c38d33a..1a3fc3863860 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -4794,13 +4794,17 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path, int level; struct extent_buffer *c; struct extent_buffer *next;
- struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_fs_info *fs_info; struct btrfs_key key; bool need_commit_sem = false; u32 nritems; int ret; int i;
if (!root)
return -EINVAL;fs_info = root->fs_info; /*
- The nowait semantics are used only for write paths, where we don't
- use the tree mod log and sequence numbers.