bcachefs: Annotate struct bucket_gens with __counted_by()

Add the __counted_by compiler attribute to the flexible array member b
to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

Use struct_size() to calculate the number of bytes to be allocated.

Update bucket_gens->nbuckets and bucket_gens->nbuckets_minus_first when
resizing.

Compile-tested only.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/buckets.c b/fs/bcachefs/buckets.c
index ec7d9a59bea9c0c204d60a0a4a2b4dd7b5739bd5..8bd17667e243451a89fd27c9d5e9e25546955348 100644 (file)
--- a/fs/bcachefs/buckets.c
+++ b/fs/bcachefs/buckets.c
@@ -1266,8 +1266,9 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 
        BUG_ON(resize && ca->buckets_nouse);
 
-       if (!(bucket_gens       = kvmalloc(sizeof(struct bucket_gens) + nbuckets,
-                                          GFP_KERNEL|__GFP_ZERO))) {
+       bucket_gens = kvmalloc(struct_size(bucket_gens, b, nbuckets),
+                              GFP_KERNEL|__GFP_ZERO);
+       if (!bucket_gens) {
                ret = -BCH_ERR_ENOMEM_bucket_gens;
                goto err;
        }
@@ -1285,11 +1286,13 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
        old_bucket_gens = rcu_dereference_protected(ca->bucket_gens, 1);
 
        if (resize) {
-               size_t n = min(bucket_gens->nbuckets, old_bucket_gens->nbuckets);
-
+               bucket_gens->nbuckets = min(bucket_gens->nbuckets,
+                                           old_bucket_gens->nbuckets);
+               bucket_gens->nbuckets_minus_first =
+                       bucket_gens->nbuckets - bucket_gens->first_bucket;
                memcpy(bucket_gens->b,
                       old_bucket_gens->b,
-                      n);
+                      bucket_gens->nbuckets);
        }
 
        rcu_assign_pointer(ca->bucket_gens, bucket_gens);

diff --git a/fs/bcachefs/buckets_types.h b/fs/bcachefs/buckets_types.h
index 28bd09a253c83e6bc1e5ac0c73550c3bc2414e8d..7174047b8e920eeb04f602081d23eda124c7cf34 100644 (file)
--- a/fs/bcachefs/buckets_types.h
+++ b/fs/bcachefs/buckets_types.h
@@ -24,7 +24,7 @@ struct bucket_gens {
        u16                     first_bucket;
        size_t                  nbuckets;
        size_t                  nbuckets_minus_first;
-       u8                      b[];
+       u8                      b[] __counted_by(nbuckets);
 };
 
 struct bch_dev_usage {