From: Zijie Zhao <zzjas98@gmail.com>
To: kent.overstreet@linux.dev, bfoster@redhat.com
Cc: linux-bcachefs@vger.kernel.org, chenyuan0y@gmail.com
Subject: [fs/bcachefs] Question about memory allocation in btree_paths_realloc
Date: Wed, 20 Mar 2024 16:37:02 -0500 [thread overview]
Message-ID: <080de8c1-497c-45aa-a5a0-10dba5319c64@gmail.com> (raw)
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?
Please let us know if we missed any key information or assumption! We
appreciate your time!
Best,
Zijie
next reply other threads:[~2024-03-20 21:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-20 21:37 Zijie Zhao [this message]
2024-03-20 21:48 ` [fs/bcachefs] Question about memory allocation in btree_paths_realloc Kent Overstreet
2024-03-20 21:50 ` Zijie Zhao
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