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

[Su Hui]

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