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@xxxxxxxxxxxxxxx
Fixes: d96b34248c2f ("btrfs: make send work with concurrent block group relocation")
Signed-off-by: Ma Ke <make24@xxxxxxxxxxx>
---
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.
