When searching the extent tree to gather the needed extent info, btrfs_search_old_slot() 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_search_old_slot().
Found by code review.
Cc: stable@vger.kernel.org Fixes: 0b246afa62b0 ("btrfs: root->fs_info cleanup, add fs_info convenience variables") 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 3dc5a35dd19b..4e2e1c38d33a 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2232,7 +2232,7 @@ ALLOW_ERROR_INJECTION(btrfs_search_slot, ERRNO); int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, struct btrfs_path *p, u64 time_seq) { - struct btrfs_fs_info *fs_info = root->fs_info; + struct btrfs_fs_info *fs_info; struct extent_buffer *b; int slot; int ret; @@ -2241,6 +2241,10 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, int lowest_unlock = 1; u8 lowest_level = 0;
+ if (!root) + return -EINVAL; + + fs_info = root->fs_info; lowest_level = p->lowest_level; WARN_ON(p->nodes[0] != NULL); ASSERT(!p->nowait);
在 2025/2/24 18:21, Ma Ke 写道:
When searching the extent tree to gather the needed extent info, btrfs_search_old_slot() 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_search_old_slot().
I do not think it's the case anymore.
Commit 6aecd91a5c5b ("btrfs: avoid NULL pointer dereference if no valid extent tree") has introduced a check for the extent root, at the very beginning of scrub_find_fill_first_stripe().
Thus it will never call find_first_extent_item() to search the NULL extent tree.
Or do you have another case where we need to search extent tree meanwhile the fs is mounted with rescue=ibadroots?
Thanks, Qu
Found by code review.
Cc: stable@vger.kernel.org Fixes: 0b246afa62b0 ("btrfs: root->fs_info cleanup, add fs_info convenience variables") 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 3dc5a35dd19b..4e2e1c38d33a 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2232,7 +2232,7 @@ ALLOW_ERROR_INJECTION(btrfs_search_slot, ERRNO); int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, struct btrfs_path *p, u64 time_seq) {
- struct btrfs_fs_info *fs_info = root->fs_info;
- struct btrfs_fs_info *fs_info; struct extent_buffer *b; int slot; int ret;
@@ -2241,6 +2241,10 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, int lowest_unlock = 1; u8 lowest_level = 0;
- if (!root)
return -EINVAL;- fs_info = root->fs_info; lowest_level = p->lowest_level; WARN_ON(p->nodes[0] != NULL); ASSERT(!p->nowait);
On Mon, Feb 24, 2025 at 7:52 AM Ma Ke make24@iscas.ac.cn wrote:
When searching the extent tree to gather the needed extent info, btrfs_search_old_slot() 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_search_old_slot().
Found by code review.
Cc: stable@vger.kernel.org Fixes: 0b246afa62b0 ("btrfs: root->fs_info cleanup, add fs_info convenience variables")
Besides what was already pointed out by Qu, that you should explain how can the root be NULL, etc, this is also a completely wrong commit in the Fixes tag.
You can only get a NULL extent root if the fs was mounted with ignorebadroots and there is a corruption in the extent tree (or maybe we got some transient error while attempting to read it like -ENOMEM).
So ignorebadroots was introduced in commit 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots") which is dated from 2020, but that commit you added in the Fixes tag is from 2016, back when we could never have successfully mounted the fs with a NULL extent root.
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 3dc5a35dd19b..4e2e1c38d33a 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2232,7 +2232,7 @@ ALLOW_ERROR_INJECTION(btrfs_search_slot, ERRNO); int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, struct btrfs_path *p, u64 time_seq) {
struct btrfs_fs_info *fs_info = root->fs_info;
struct btrfs_fs_info *fs_info; struct extent_buffer *b; int slot; int ret;@@ -2241,6 +2241,10 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key, int lowest_unlock = 1; u8 lowest_level = 0;
if (!root)return -EINVAL;fs_info = root->fs_info; lowest_level = p->lowest_level; WARN_ON(p->nodes[0] != NULL); ASSERT(!p->nowait);-- 2.25.1
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