[PATCH][next] bcachefs: Replace zero-length arrays with flexible-array members

[PATCH][next] bcachefs: Replace zero-length arrays with flexible-array members

[Gustavo A. R. Silva]

Fake flexible arrays (zero-length and one-element arrays) are
deprecated, and should be replaced by flexible-array members.

So, replace zero-length arrays with flexible-array members
in multiple structures.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 fs/bcachefs/bcachefs_ioctl.h | 4 ++--
 fs/bcachefs/io_read.c        | 2 +-
 fs/bcachefs/move.c           | 2 +-
 fs/bcachefs/replicas_types.h | 2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/bcachefs/bcachefs_ioctl.h b/fs/bcachefs/bcachefs_ioctl.h
index 44ba7a87aea7..43822c17297c 100644
--- a/fs/bcachefs/bcachefs_ioctl.h
+++ b/fs/bcachefs/bcachefs_ioctl.h
@@ -276,7 +276,7 @@ struct bch_ioctl_fs_usage {
 	__u32			replica_entries_bytes;
 	__u32			pad;
 
-	struct bch_replicas_usage replicas[0];
+	struct bch_replicas_usage replicas[];
 };
 
 /*
@@ -313,7 +313,7 @@ struct bch_ioctl_dev_usage_v2 {
 	__u32			bucket_size;
 	__u64			nr_buckets;
 
-	struct bch_ioctl_dev_usage_type  d[0];
+	struct bch_ioctl_dev_usage_type d[];
 };
 
 /*
diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index 3281c4dd1d52..4c9eaf7cea8d 100644
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -80,7 +80,7 @@ struct promote_op {
 	struct bpos		pos;
 
 	struct data_update	write;
-	struct bio_vec		bi_inline_vecs[0]; /* must be last */
+	struct bio_vec		bi_inline_vecs[]; /* must be last */
 };
 
 static const struct rhashtable_params bch_promote_params = {
diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c
index c5518a866276..5a693c3e2ed2 100644
--- a/fs/bcachefs/move.c
+++ b/fs/bcachefs/move.c
@@ -81,7 +81,7 @@ struct moving_io {
 
 	struct data_update		write;
 	/* Must be last since it is variable size */
-	struct bio_vec			bi_inline_vecs[0];
+	struct bio_vec			bi_inline_vecs[];
 };
 
 static void move_free(struct moving_io *io)
diff --git a/fs/bcachefs/replicas_types.h b/fs/bcachefs/replicas_types.h
index 030324078bba..ac90d142c4e8 100644
--- a/fs/bcachefs/replicas_types.h
+++ b/fs/bcachefs/replicas_types.h
@@ -21,7 +21,7 @@ struct replicas_delta_list {
 	u64			nr_inodes;
 	u64			persistent_reserved[BCH_REPLICAS_MAX];
 	struct			{} memset_end;
-	struct replicas_delta	d[0];
+	struct replicas_delta	d[];
 };
 
 #endif /* _BCACHEFS_REPLICAS_TYPES_H */
-- 
2.34.1

Re: [PATCH][next] bcachefs: Replace zero-length arrays with flexible-array members

[Kees Cook]

On Tue, Nov 28, 2023 at 12:22:55PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are
> deprecated, and should be replaced by flexible-array members.
> 
> So, replace zero-length arrays with flexible-array members
> in multiple structures.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

These look like straight-forward conversions. Thanks!

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH][next] bcachefs: Replace zero-length arrays with flexible-array members

[Gustavo A. R. Silva]

On 11/29/23 14:15, Kees Cook wrote:
> On Tue, Nov 28, 2023 at 12:22:55PM -0600, Gustavo A. R. Silva wrote:
>> Fake flexible arrays (zero-length and one-element arrays) are
>> deprecated, and should be replaced by flexible-array members.
>>
>> So, replace zero-length arrays with flexible-array members
>> in multiple structures.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> These look like straight-forward conversions. Thanks!

Yep, these also fix a buch of -Warray-bounds warnings reported
by 0-day:

https://lore.kernel.org/lkml/202311290720.TzNYq81c-lkp@intel.com/

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 

Thanks!
--
Gustavo

Re: [PATCH][next] bcachefs: Replace zero-length arrays with flexible-array members

[Kent Overstreet]

On Tue, Nov 28, 2023 at 12:22:55PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are
> deprecated, and should be replaced by flexible-array members.
> 
> So, replace zero-length arrays with flexible-array members
> in multiple structures.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

There are some ZLAs I hadn't converted because they led to new warnings
- in particular, array of flexible members.

I don't think that applies to any of the ones you changed
(replicas_delta_list, maybe?) - but it's something we need to figure
out if we're getting serious about this.