[PATCH AUTOSEL 6.1 11/11] 9p: v9fs_listxattr: fix %s null argument warning

From: Dominique Martinet <asmadeus@codewreck.org>

[ Upstream commit 9b5c6281838fc84683dd99b47302d81fce399918 ]

W=1 warns about null argument to kprintf:
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 an empty string instead of :
 - this is ok 9p-wise because p9pdu_vwritef serializes a null string
and an empty string the same way (one '0' word for length)
 - since this degrades the print statements, add new single quotes for
xattr's name delimter (Old: "file = (null)", new: "file = ''")

Link: https://lore.kernel.org/r/20231008060138.517057-1-suhui@nfschina.com (local)
Suggested-by: Su Hui <redacted>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Acked-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Message-ID: [off-list ref]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/9p/xattr.c   | 5 +++--
 net/9p/client.c | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/9p/xattr.c b/fs/9p/xattr.c
index 2807bb63f7802..3b9aa61de8c2d 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c

@@ -65,7 +65,7 @@ ssize_t v9fs_xattr_get(struct dentry *dentry, const char *name,
 	struct p9_fid *fid;
 	int ret;
 
-	p9_debug(P9_DEBUG_VFS, "name = %s value_len = %zu\n",
+	p9_debug(P9_DEBUG_VFS, "name = '%s' value_len = %zu\n",
 		 name, buffer_size);
 	fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))

@@ -136,7 +136,8 @@ 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);
+	/* Txattrwalk with an empty string lists xattrs instead */
+	return v9fs_xattr_get(dentry, "", buffer, buffer_size);
 }
 
 static int v9fs_xattr_handler_get(const struct xattr_handler *handler,

diff --git a/net/9p/client.c b/net/9p/client.c
index af59c3f2ec2e7..b86629deea438 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c

@@ -1985,7 +1985,7 @@ struct p9_fid *p9_client_xattrwalk(struct p9_fid *file_fid,
 		goto error;
 	}
 	p9_debug(P9_DEBUG_9P,
-		 ">>> TXATTRWALK file_fid %d, attr_fid %d name %s\n",
+		 ">>> TXATTRWALK file_fid %d, attr_fid %d name '%s'\n",
 		 file_fid->fid, attr_fid->fid, attr_name);
 
 	req = p9_client_rpc(clnt, P9_TXATTRWALK, "dds",

-- 
2.42.0