On 4/16/2023 2:38 PM, Paulo Alcantara wrote:
@server->origin_fullpath already contains the tree name + optional
prefix, so avoid calling __build_path_from_dentry_optional_prefix() as
it might end up duplicating prefix path from @cifs_sb->prepath into
final full path.
Instead, generate DFS full path by simply merging
@server->origin_fullpath with dentry's path.
This fixes the following case
mount.cifs //root/dfs/dir /mnt/ -o ...
ls /mnt/link
where cifs_dfs_do_automount() will call smb3_parse_devname() with
@devname set to "//root/dfs/dir/link" instead of
"//root/dfs/dir/dir/link".
Fixes: 7ad54b98fc1f ("cifs: use origin fullpath for automounts")
Signed-off-by: Paulo Alcantara (SUSE) <pc@xxxxxxxxxxxxx>
---
FYI, updated DFS tests to include the above case and avoid regressions.
fs/cifs/cifs_dfs_ref.c | 2 --
fs/cifs/dfs.h | 22 ++++++++++++++++++----
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index cb40074feb3e..0329a907bdfe 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -171,8 +171,6 @@ static struct vfsmount *cifs_dfs_do_automount(struct path *path)
mnt = ERR_CAST(full_path);
goto out;
}
-
- convert_delimiter(full_path, '/');
cifs_dbg(FYI, "%s: full_path: %s\n", __func__, full_path);
tmp = *cur_ctx;
diff --git a/fs/cifs/dfs.h b/fs/cifs/dfs.h
index 13f26e01f7b9..0b8cbf721fff 100644
--- a/fs/cifs/dfs.h
+++ b/fs/cifs/dfs.h
@@ -34,19 +34,33 @@ static inline int dfs_get_referral(struct cifs_mount_ctx *mnt_ctx, const char *p
cifs_remap(cifs_sb), path, ref, tl);
}
+/* Return DFS full path out of a dentry set for automount */
static inline char *dfs_get_automount_devname(struct dentry *dentry, void *page)
{
struct cifs_sb_info *cifs_sb = CIFS_SB(dentry->d_sb);
struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
struct TCP_Server_Info *server = tcon->ses->server;
+ size_t len;
+ char *s;
if (unlikely(!server->origin_fullpath))
return ERR_PTR(-EREMOTE);
- return __build_path_from_dentry_optional_prefix(dentry, page,
- server->origin_fullpath,
- strlen(server->origin_fullpath),
- true);
+ s = dentry_path_raw(dentry, page, PATH_MAX);
+ if (IS_ERR(s))
+ return s;
+ /* for root, we want "" */
+ if (!s[1])
+ s++;
The above pointer increment is really hard to understand, given the
comment. So, if the result is a single-character path, presumably "/",
advance the pointer so it becomes a null string? It's not obvious from
this code and comment.
+ len = strlen(server->origin_fullpath);
+ if (s < (char *)page + len)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ s -= len;
This looks doubly dangerous. What prevents the pointer from moving
backwards to ahead of the buffer? Especially in light of the above
root-only adjustment?
+ memcpy(s, server->origin_fullpath, len);
+ convert_delimiter(s, '/');
+ return s;
}
static inline void dfs_put_root_smb_sessions(struct list_head *head)
Tom.
