From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
To: Jan Kara <jack@suse.cz>, Amir Goldstein <amir73il@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
linux-hardening@vger.kernel.org,
Kees Cook <keescook@chromium.org>
Subject: [PATCH][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning
Date: Tue, 5 Mar 2024 16:18:46 -0600 [thread overview]
Message-ID: <ZeeaRuTpuxInH6ZB@neat> (raw)
-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.
There is currently a local structure `f` that is using a flexible
`struct file_handle` as header for an on-stack place-holder for the
flexible-array member `unsigned char f_handle[];`.
struct {
struct file_handle handle;
u8 pad[MAX_HANDLE_SZ];
} f;
However, we are deprecating flexible arrays in the middle of another
struct. So, in order to avoid this, we use the `struct_group_tagged()`
helper to separate the flexible array from the rest of the members in
the flexible structure:
struct file_handle {
struct_group_tagged(file_handle_hdr, hdr,
... the rest of the members
);
unsigned char f_handle[];
};
With the change described above, we can now declare an object of the
type of the tagged struct, without embedding the flexible array in the
middle of another struct:
struct {
struct file_handle_hdr handle;
u8 pad[MAX_HANDLE_SZ];
} f;
We also use `container_of()` whenever we need to retrieve a pointer to
the flexible structure, through which the flexible-array member can be
accessed, as in this case.
So, with these changes, fix the following warning:
fs/notify/fdinfo.c: In function ‘show_mark_fhandle’:
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]
45 | struct file_handle handle;
| ^~~~~~
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
fs/notify/fdinfo.c | 8 +++++---
include/linux/fs.h | 6 ++++--
2 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index 5c430736ec12..740f5e68b397 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -42,15 +42,17 @@ static void show_fdinfo(struct seq_file *m, struct file *f,
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
{
struct {
- struct file_handle handle;
+ struct file_handle_hdr handle;
u8 pad[MAX_HANDLE_SZ];
} f;
+ struct file_handle *handle = container_of(&f.handle,
+ struct file_handle, hdr);
int size, ret, i;
f.handle.handle_bytes = sizeof(f.pad);
size = f.handle.handle_bytes >> 2;
- ret = exportfs_encode_fid(inode, (struct fid *)f.handle.f_handle, &size);
+ ret = exportfs_encode_fid(inode, (struct fid *)handle->f_handle, &size);
if ((ret == FILEID_INVALID) || (ret < 0)) {
WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
return;
@@ -63,7 +65,7 @@ static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
f.handle.handle_bytes, f.handle.handle_type);
for (i = 0; i < f.handle.handle_bytes; i++)
- seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
+ seq_printf(m, "%02x", (int)handle->f_handle[i]);
}
#else
static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 00fc429b0af0..7c131bcd948f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1030,8 +1030,10 @@ struct file {
__attribute__((aligned(4))); /* lest something weird decides that 2 is OK */
struct file_handle {
- __u32 handle_bytes;
- int handle_type;
+ struct_group_tagged(file_handle_hdr, hdr,
+ __u32 handle_bytes;
+ int handle_type;
+ );
/* file identifier */
unsigned char f_handle[];
};
--
2.34.1
next reply other threads:[~2024-03-05 22:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 22:18 Gustavo A. R. Silva [this message]
2024-03-05 23:52 ` [PATCH][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning Kees Cook
2024-03-06 7:36 ` Amir Goldstein
2024-03-06 15:42 ` Gustavo A. R. Silva
2024-03-06 15:42 ` Gustavo A. R. Silva
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