bcachefs: fix null-ptr-deref in have_stripes()

c->btree_roots_known[i].b can be NULL. In this case, a NULL pointer dereference
occurs, so you need to add code to check the variable.

Reported-by: syzbot+b468b9fef56949c3b528@syzkaller.appspotmail.com
Fixes: 7773df19c35f ("bcachefs: metadata version bucket_stripe_sectors")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c
index ae715ff..8767c33 100644 (file)
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -143,6 +143,9 @@ UPGRADE_TABLE()
 
 static int have_stripes(struct bch_fs *c)
 {
+       if (IS_ERR_OR_NULL(c->btree_roots_known[BTREE_ID_stripes].b))
+               return 0;
+
        return !btree_node_fake(c->btree_roots_known[BTREE_ID_stripes].b);
 }