LinuxLists.cc - [PATCH][next] bcachefs: Use DECLARE_FLEX_ARRAY() helper and fix multiple -Warray-bounds warnings

2023-11-06 22:27:22

Subject: [PATCH][next] bcachefs: Use DECLARE_FLEX_ARRAY() helper and fix multiple -Warray-bounds warnings

Transform zero-length array `s` into a proper flexible-array
member in `struct snapshot_table` via the DECLARE_FLEX_ARRAY()
helper; and fix tons of the following -Warray-bounds warnings:

fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
fs/bcachefs/snapshot.c:135:70: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]

This helps with the ongoing efforts to globally enable -Warray-bounds.

Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
fs/bcachefs/subvolume_types.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/bcachefs/subvolume_types.h b/fs/bcachefs/subvolume_types.h
index 86833445af20..2d2e66a4e468 100644
--- a/fs/bcachefs/subvolume_types.h
+++ b/fs/bcachefs/subvolume_types.h
@@ -20,7 +20,7 @@ struct snapshot_t {
};

struct snapshot_table {
- struct snapshot_t s[0];
+ DECLARE_FLEX_ARRAY(struct snapshot_t, s);
};

typedef struct {
--
2.34.1

2023-11-07 00:08:27

by Kees Cook

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Subject: Re: [PATCH][next] bcachefs: Use DECLARE_FLEX_ARRAY() helper and fix multiple -Warray-bounds warnings

On Mon, Nov 06, 2023 at 04:27:02PM -0600, Gustavo A. R. Silva wrote:
> Transform zero-length array `s` into a proper flexible-array
> member in `struct snapshot_table` via the DECLARE_FLEX_ARRAY()
> helper; and fix tons of the following -Warray-bounds warnings:
>
> fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
> fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
> fs/bcachefs/snapshot.c:135:70: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
> fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
> fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
> fs/bcachefs/snapshot.h:36:21: warning: array subscript <unknown> is outside array bounds of 'struct snapshot_t[0]' [-Warray-bounds=]
>
> This helps with the ongoing efforts to globally enable -Warray-bounds.
>
> Signed-off-by: Gustavo A. R. Silva <[email protected]>
> ---
> fs/bcachefs/subvolume_types.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/subvolume_types.h b/fs/bcachefs/subvolume_types.h
> index 86833445af20..2d2e66a4e468 100644
> --- a/fs/bcachefs/subvolume_types.h
> +++ b/fs/bcachefs/subvolume_types.h
> @@ -20,7 +20,7 @@ struct snapshot_t {
> };
>
> struct snapshot_table {
> - struct snapshot_t s[0];
> + DECLARE_FLEX_ARRAY(struct snapshot_t, s);
> };

Yup, this is the current way forward for 0-to-flex transformations in
unions or alone in structs (until it's supported correctly by GCC and
Clang, which is in progress).

Reviewed-by: Kees Cook <[email protected]>

-Kees

--
Kees Cook

2023-11-07 00:43:33

by Kent Overstreet

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