2023-10-25 10:36:38

by Dominique Martinet

[permalink] [raw]
Subject: [PATCH v2 2/3] 9p: v9fs_listxattr: fix %s null argument warning

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 = ''")

Signed-off-by: Dominique Martinet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Suggested-by: Su Hui <[email protected]>
Acked-by: Christian Schoenebeck <[email protected]>
---
v1->v2:
- add comment that txattrwalk with an empty string gets the list

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 e00cf8109b3f..3c4572ef3a48 100644
--- a/fs/9p/xattr.c
+++ b/fs/9p/xattr.c
@@ -68,7 +68,7 @@ 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))
@@ -139,7 +139,8 @@ 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 86bbc7147fc1..9c2bc15e3cfa 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -1979,7 +1979,7 @@ 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",
--
2.41.0