| Message ID | 20250224075142.2959155-1-make24@iscas.ac.cn (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | btrfs: add a sanity check for btrfs root in btrfs_search_old_slot() | expand |
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 > >
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);
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(-)