On Wed, Mar 20, 2024 at 04:37:02PM -0500, Zijie Zhao wrote: > Dear BCACHEFS maintainers, > > We encountered an unusual usage of kzalloc in btree_paths_realloc while > performing a static analysis for kernel code. > > > https://elixir.bootlin.com/linux/latest/source/fs/bcachefs/btree_iter.c#L1523 > > ``` > static noinline void btree_paths_realloc(struct btree_trans *trans) > { > unsigned nr = trans->nr_paths * 2; > > void *p = kzalloc(BITS_TO_LONGS(nr) * sizeof(unsigned long) + > sizeof(struct btree_trans_paths) + > nr * sizeof(struct btree_path) + > nr * sizeof(btree_path_idx_t) + 8 + > nr * sizeof(struct btree_insert_entry), > GFP_KERNEL|__GFP_NOFAIL); > > unsigned long *paths_allocated = p; > memcpy(paths_allocated, trans->paths_allocated, > BITS_TO_LONGS(trans->nr_paths) * sizeof(unsigned long)); > ... > } > ``` > > Here kzalloc might return NULL in case of out-of-memory, making > memcpy(NULL,...) to have undefined behavior. Would a NULL check be needed > here?
See that __GFP_NOFAIL?
