cifs: improve checking of DFS links over STATUS_OBJECT_NAME_INVALID

Do not map STATUS_OBJECT_NAME_INVALID to -EREMOTE under non-DFS
shares, or 'nodfs' mounts or CONFIG_CIFS_DFS_UPCALL=n builds.
Otherwise, in the slow path, get a referral to figure out whether it
is an actual DFS link.

This could be simply reproduced under a non-DFS share by running the
following

  $ mount.cifs //srv/share /mnt -o ...
  $ cat /mnt/$(printf '\U110000')
  cat: '/mnt/'$'\364\220\200\200': Object is remote

Fixes: c877ce47e137 ("cifs: reduce roundtrips on create/qinfo requests")
CC: stable@vger.kernel.org # 6.2
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index b7a36eb..20a2f0f 100644 (file)
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -667,11 +667,21 @@ static inline int get_dfs_path(const unsigned int xid, struct cifs_ses *ses,
 int match_target_ip(struct TCP_Server_Info *server,
                    const char *share, size_t share_len,
                    bool *result);
-
-int cifs_dfs_query_info_nonascii_quirk(const unsigned int xid,
-                                      struct cifs_tcon *tcon,
-                                      struct cifs_sb_info *cifs_sb,
-                                      const char *dfs_link_path);
+int cifs_inval_name_dfs_link_error(const unsigned int xid,
+                                  struct cifs_tcon *tcon,
+                                  struct cifs_sb_info *cifs_sb,
+                                  const char *full_path,
+                                  bool *islink);
+#else
+static inline int cifs_inval_name_dfs_link_error(const unsigned int xid,
+                                  struct cifs_tcon *tcon,
+                                  struct cifs_sb_info *cifs_sb,
+                                  const char *full_path,
+                                  bool *islink)
+{
+       *islink = false;
+       return 0;
+}
 #endif
 
 static inline int cifs_create_options(struct cifs_sb_info *cifs_sb, int options)

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 2905734..0c6c1fc 100644 (file)
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -21,6 +21,7 @@
 #include "cifsfs.h"
 #ifdef CONFIG_CIFS_DFS_UPCALL
 #include "dns_resolve.h"
+#include "dfs_cache.h"
 #endif
 #include "fs_context.h"
 #include "cached_dir.h"
@@ -1198,4 +1199,70 @@ int cifs_update_super_prepath(struct cifs_sb_info *cifs_sb, char *prefix)
        cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_USE_PREFIX_PATH;
        return 0;
 }
+
+/*
+ * Handle weird Windows SMB server behaviour. It responds with
+ * STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request for
+ * "\<server>\<dfsname>\<linkpath>" DFS reference, where <dfsname> contains
+ * non-ASCII unicode symbols.
+ */
+int cifs_inval_name_dfs_link_error(const unsigned int xid,
+                                  struct cifs_tcon *tcon,
+                                  struct cifs_sb_info *cifs_sb,
+                                  const char *full_path,
+                                  bool *islink)
+{
+       struct cifs_ses *ses = tcon->ses;
+       size_t len;
+       char *path;
+       char *ref_path;
+
+       *islink = false;
+
+       /*
+        * Fast path - skip check when @full_path doesn't have a prefix path to
+        * look up or tcon is not DFS.
+        */
+       if (strlen(full_path) < 2 || !cifs_sb ||
+           (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS) ||
+           !is_tcon_dfs(tcon) || !ses->server->origin_fullpath)
+               return 0;
+
+       /*
+        * Slow path - tcon is DFS and @full_path has prefix path, so attempt
+        * to get a referral to figure out whether it is an DFS link.
+        */
+       len = strnlen(tcon->tree_name, MAX_TREE_SIZE + 1) + strlen(full_path) + 1;
+       path = kmalloc(len, GFP_KERNEL);
+       if (!path)
+               return -ENOMEM;
+
+       scnprintf(path, len, "%s%s", tcon->tree_name, full_path);
+       ref_path = dfs_cache_canonical_path(path + 1, cifs_sb->local_nls,
+                                           cifs_remap(cifs_sb));
+       kfree(path);
+
+       if (IS_ERR(ref_path)) {
+               if (PTR_ERR(ref_path) != -EINVAL)
+                       return PTR_ERR(ref_path);
+       } else {
+               struct dfs_info3_param *refs = NULL;
+               int num_refs = 0;
+
+               /*
+                * XXX: we are not using dfs_cache_find() here because we might
+                * end filling all the DFS cache and thus potentially
+                * removing cached DFS targets that the client would eventually
+                * need during failover.
+                */
+               if (ses->server->ops->get_dfs_refer &&
+                   !ses->server->ops->get_dfs_refer(xid, ses, ref_path, &refs,
+                                                    &num_refs, cifs_sb->local_nls,
+                                                    cifs_remap(cifs_sb)))
+                       *islink = refs[0].server_type == DFS_TYPE_LINK;
+               free_dfs_info_array(refs, num_refs);
+               kfree(ref_path);
+       }
+       return 0;
+}
 #endif

diff --git a/fs/cifs/smb2inode.c b/fs/cifs/smb2inode.c
index 37b4cd5..9b95629 100644 (file)
--- a/fs/cifs/smb2inode.c
+++ b/fs/cifs/smb2inode.c
@@ -527,12 +527,13 @@ int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
                         struct cifs_sb_info *cifs_sb, const char *full_path,
                         struct cifs_open_info_data *data, bool *adjust_tz, bool *reparse)
 {
-       int rc;
        __u32 create_options = 0;
        struct cifsFileInfo *cfile;
        struct cached_fid *cfid = NULL;
        struct kvec err_iov[3] = {};
        int err_buftype[3] = {};
+       bool islink;
+       int rc, rc2;
 
        *adjust_tz = false;
        *reparse = false;
@@ -580,15 +581,15 @@ int smb2_query_path_info(const unsigned int xid, struct cifs_tcon *tcon,
                                              SMB2_OP_QUERY_INFO, cfile, NULL, NULL,
                                              NULL, NULL);
                        goto out;
-               } else if (rc != -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) &&
-                          hdr->Status == STATUS_OBJECT_NAME_INVALID) {
-                       /*
-                        * Handle weird Windows SMB server behaviour. It responds with
-                        * STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
-                        * for "\<server>\<dfsname>\<linkpath>" DFS reference,
-                        * where <dfsname> contains non-ASCII unicode symbols.
-                        */
-                       rc = -EREMOTE;
+               } else if (rc != -EREMOTE && hdr->Status == STATUS_OBJECT_NAME_INVALID) {
+                       rc2 = cifs_inval_name_dfs_link_error(xid, tcon, cifs_sb,
+                                                            full_path, &islink);
+                       if (rc2) {
+                               rc = rc2;
+                               goto out;
+                       }
+                       if (islink)
+                               rc = -EREMOTE;
                }
                if (rc == -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) && cifs_sb &&
                    (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS))

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f79b075..6dfb865 100644 (file)
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -796,7 +796,6 @@ static int
 smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
                        struct cifs_sb_info *cifs_sb, const char *full_path)
 {
-       int rc;
        __le16 *utf16_path;
        __u8 oplock = SMB2_OPLOCK_LEVEL_NONE;
        int err_buftype = CIFS_NO_BUFFER;
@@ -804,6 +803,8 @@ smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
        struct kvec err_iov = {};
        struct cifs_fid fid;
        struct cached_fid *cfid;
+       bool islink;
+       int rc, rc2;
 
        rc = open_cached_dir(xid, tcon, full_path, cifs_sb, true, &cfid);
        if (!rc) {
@@ -833,15 +834,17 @@ smb2_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
 
                if (unlikely(!hdr || err_buftype == CIFS_NO_BUFFER))
                        goto out;
-               /*
-                * Handle weird Windows SMB server behaviour. It responds with
-                * STATUS_OBJECT_NAME_INVALID code to SMB2 QUERY_INFO request
-                * for "\<server>\<dfsname>\<linkpath>" DFS reference,
-                * where <dfsname> contains non-ASCII unicode symbols.
-                */
-               if (rc != -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) &&
-                   hdr->Status == STATUS_OBJECT_NAME_INVALID)
-                       rc = -EREMOTE;
+
+               if (rc != -EREMOTE && hdr->Status == STATUS_OBJECT_NAME_INVALID) {
+                       rc2 = cifs_inval_name_dfs_link_error(xid, tcon, cifs_sb,
+                                                            full_path, &islink);
+                       if (rc2) {
+                               rc = rc2;
+                               goto out;
+                       }
+                       if (islink)
+                               rc = -EREMOTE;
+               }
                if (rc == -EREMOTE && IS_ENABLED(CONFIG_CIFS_DFS_UPCALL) && cifs_sb &&
                    (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS))
                        rc = -EOPNOTSUPP;