2024-03-26 01:36:23

by Gustavo A. R. Silva

Subject: [PATCH v2][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning

Use the `DEFINE_FLEX()` helper for an on-stack definition of a
flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:
fs/notify/fdinfo.c:45:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Link: https://github.com/KSPP/linux/issues/202
Signed-off-by: Gustavo A. R. Silva <[email protected]>
---
Changes in v2:
- Use DEFINE_FLEX() instead of struct_group_tagged().

v1:
- Link: https://lore.kernel.org/linux-hardening/ZeeaRuTpuxInH6ZB@neat/

fs/notify/fdinfo.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index 5c430736ec12..dec553034027 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -41,29 +41,25 @@ static void show_fdinfo(struct seq_file *m, struct file *f,
#if defined(CONFIG_EXPORTFS)
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
{
- struct {
- struct file_handle handle;
- u8 pad[MAX_HANDLE_SZ];
- } f;
+ DEFINE_FLEX(struct file_handle, f, f_handle, handle_bytes, MAX_HANDLE_SZ);
int size, ret, i;

- f.handle.handle_bytes = sizeof(f.pad);
- size = f.handle.handle_bytes >> 2;
+ size = f->handle_bytes >> 2;

- ret = exportfs_encode_fid(inode, (struct fid *)f.handle.f_handle, &size);
+ ret = exportfs_encode_fid(inode, (struct fid *)f->f_handle, &size);
if ((ret == FILEID_INVALID) || (ret < 0)) {
WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
return;
}

- f.handle.handle_type = ret;
- f.handle.handle_bytes = size * sizeof(u32);
+ f->handle_type = ret;
+ f->handle_bytes = size * sizeof(u32);

seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:",
- f.handle.handle_bytes, f.handle.handle_type);
+ f->handle_bytes, f->handle_type);

- for (i = 0; i < f.handle.handle_bytes; i++)
- seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
+ for (i = 0; i < f->handle_bytes; i++)
+ seq_printf(m, "%02x", (int)f->f_handle[i]);
}
#else
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
--
2.34.1

2024-03-26 09:55:11

by Jan Kara

Subject: Re: [PATCH v2][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning

On Mon 25-03-24 19:36:02, Gustavo A. R. Silva wrote:
> Use the `DEFINE_FLEX()` helper for an on-stack definition of a
> flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
>
> So, with these changes, fix the following warning:
> fs/notify/fdinfo.c:45:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
>
> Link: https://github.com/KSPP/linux/issues/202
> Signed-off-by: Gustavo A. R. Silva <[email protected]>

Nice! I've added the patch to my tree.

Honza

> ---
> Changes in v2:
> - Use DEFINE_FLEX() instead of struct_group_tagged().
>
> v1:
> - Link: https://lore.kernel.org/linux-hardening/ZeeaRuTpuxInH6ZB@neat/
>
> fs/notify/fdinfo.c | 20 ++++++++------------
> 1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
> index 5c430736ec12..dec553034027 100644
> --- a/fs/notify/fdinfo.c
> +++ b/fs/notify/fdinfo.c
> @@ -41,29 +41,25 @@ static void show_fdinfo(struct seq_file *m, struct file *f,
> #if defined(CONFIG_EXPORTFS)
> static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
> {
> - struct {
> - struct file_handle handle;
> - u8 pad[MAX_HANDLE_SZ];
> - } f;
> + DEFINE_FLEX(struct file_handle, f, f_handle, handle_bytes, MAX_HANDLE_SZ);
> int size, ret, i;
>
> - f.handle.handle_bytes = sizeof(f.pad);
> - size = f.handle.handle_bytes >> 2;
> + size = f->handle_bytes >> 2;
>
> - ret = exportfs_encode_fid(inode, (struct fid *)f.handle.f_handle, &size);
> + ret = exportfs_encode_fid(inode, (struct fid *)f->f_handle, &size);
> if ((ret == FILEID_INVALID) || (ret < 0)) {
> WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
> return;
> }
>
> - f.handle.handle_type = ret;
> - f.handle.handle_bytes = size * sizeof(u32);
> + f->handle_type = ret;
> + f->handle_bytes = size * sizeof(u32);
>
> seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:",
> - f.handle.handle_bytes, f.handle.handle_type);
> + f->handle_bytes, f->handle_type);
>
> - for (i = 0; i < f.handle.handle_bytes; i++)
> - seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
> + for (i = 0; i < f->handle_bytes; i++)
> + seq_printf(m, "%02x", (int)f->f_handle[i]);
> }
> #else
> static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
> --
> 2.34.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR