Re: [PATCH] fs/9p/xattr.c: avoid format-overflow warning

From: Su Hui
Date: Mon Oct 09 2023 - 21:20:22 EST


On 2023/10/10 02:34, Christian Schoenebeck wrote:
On Sunday, October 8, 2023 8:01:39 AM CEST Su Hui wrote:
with gcc and W=1 option, there's a warning like this:

In file included from fs/9p/xattr.c:12:
In function ‘v9fs_xattr_get’,
inlined from ‘v9fs_listxattr’ at fs/9p/xattr.c:142:9:
include/net/9p/9p.h:55:2: error: ‘%s’ directive argument is null
[-Werror=format-overflow=]
55 | _p9_debug(level, __func__, fmt, ##__VA_ARGS__)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

use "" replace NULL to silence this warning.

Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
---
fs/9p/xattr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index e00cf8109b3f..d995ee080835 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -139,7 +139,7 @@ int v9fs_fid_xattr_set(struct p9_fid *fid, const char *name,
ssize_t v9fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
{
- return v9fs_xattr_get(dentry, NULL, buffer, buffer_size);
+ return v9fs_xattr_get(dentry, "", buffer, buffer_size);
}
static int v9fs_xattr_handler_get(const struct xattr_handler *handler,

Mmm, that's not the same is it? Have you tested this change?
Oh, sorry.  That's not the same and I just tested compilation.

Currently this function causes a 'Txattrwalk' 9p message to be sent to 9p
server with its name[s] field being NULL, and the latter being the magical
hint to 9p server to not send an attribute, but rather the list of attributes.

With your change I would assume that it would rather ask server for one
attribute called "". I have not tested myself, just worrying that it might
break behaviour.
Got it, I made a mistake there. Thanks for your explanation.
Sorry for the noise again.

Su Hui