cifs: set DFS root session in cifs_get_smb_ses()

Set the DFS root session pointer earlier when creating a new SMB
session to prevent racing with smb2_reconnect(), cifs_reconnect_tcon()
and DFS cache refresher.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Cc: stable@vger.kernel.org # 6.2
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/cifs_dfs_ref.c

@@ -179,6 +179,7 @@ static struct vfsmount *cifs_dfs_do_automount(struct path *path)
  tmp.source = full_path;
  tmp.leaf_fullpath = NULL;
  tmp.UNC = tmp.prepath = NULL;
+ tmp.dfs_root_ses = NULL;
 
  rc = smb3_fs_context_dup(ctx, &tmp);
  if (rc) {

fs/cifs/cifsglob.h

@@ -1749,7 +1749,6 @@ struct cifs_mount_ctx {
  struct TCP_Server_Info *server;
  struct cifs_ses *ses;
  struct cifs_tcon *tcon;
- struct cifs_ses *root_ses;
  uuid_t mount_id;
  char *origin_fullpath, *leaf_fullpath;
 };

fs/cifs/connect.c

@@ -2229,6 +2229,7 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
  * need to lock before changing something in the session.
  */
  spin_lock(&cifs_tcp_ses_lock);
+ ses->dfs_root_ses = ctx->dfs_root_ses;
  list_add(&ses->smb_ses_list, &server->smb_ses_list);
  spin_unlock(&cifs_tcp_ses_lock);
 

fs/cifs/dfs.c

@@ -95,25 +95,22 @@ static int get_session(struct cifs_mount_ctx *mnt_ctx, const char *full_path)
  ctx->leaf_fullpath = (char *)full_path;
  rc = cifs_mount_get_session(mnt_ctx);
  ctx->leaf_fullpath = NULL;
- if (!rc) {
- struct cifs_ses *ses = mnt_ctx->ses;
 
- mutex_lock(&ses->session_mutex);
- ses->dfs_root_ses = mnt_ctx->root_ses;
- mutex_unlock(&ses->session_mutex);
- }
  return rc;
 }
 
 static void set_root_ses(struct cifs_mount_ctx *mnt_ctx)
 {
- if (mnt_ctx->ses) {
+ struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
+ struct cifs_ses *ses = mnt_ctx->ses;
+
+ if (ses) {
  spin_lock(&cifs_tcp_ses_lock);
- mnt_ctx->ses->ses_count++;
+ ses->ses_count++;
  spin_unlock(&cifs_tcp_ses_lock);
- dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, mnt_ctx->ses);
+ dfs_cache_add_refsrv_session(&mnt_ctx->mount_id, ses);
  }
- mnt_ctx->root_ses = mnt_ctx->ses;
+ ctx->dfs_root_ses = mnt_ctx->ses;
 }
 
 static int get_dfs_conn(struct cifs_mount_ctx *mnt_ctx, const char *ref_path, const char *full_path,
@@ -260,7 +257,7 @@ int dfs_mount_share(struct cifs_mount_ctx *mnt_ctx, bool *isdfs)
  rc = get_session(mnt_ctx, NULL);
  if (rc)
  return rc;
- mnt_ctx->root_ses = mnt_ctx->ses;
+ ctx->dfs_root_ses = mnt_ctx->ses;
  /*
  * If called with 'nodfs' mount option, then skip DFS resolving. Otherwise unconditionally
  * try to get an DFS referral (even cached) to determine whether it is an DFS mount.

fs/cifs/dfs.h

@@ -22,9 +22,10 @@ static inline char *dfs_get_path(struct cifs_sb_info *cifs_sb, const char *path)
 static inline int dfs_get_referral(struct cifs_mount_ctx *mnt_ctx, const char *path,
  struct dfs_info3_param *ref, struct dfs_cache_tgt_list *tl)
 {
+ struct smb3_fs_context *ctx = mnt_ctx->fs_ctx;
  struct cifs_sb_info *cifs_sb = mnt_ctx->cifs_sb;
 
- return dfs_cache_find(mnt_ctx->xid, mnt_ctx->root_ses, cifs_sb->local_nls,
+ return dfs_cache_find(mnt_ctx->xid, ctx->dfs_root_ses, cifs_sb->local_nls,
  cifs_remap(cifs_sb), path, ref, tl);
 }
 

fs/cifs/fs_context.h

@@ -265,6 +265,7 @@ struct smb3_fs_context {
  bool rootfs:1; /* if it's a SMB root file system */
  bool witness:1; /* use witness protocol */
  char *leaf_fullpath;
+ struct cifs_ses *dfs_root_ses;
 };
 
 extern const struct fs_parameter_spec smb3_fs_parameters[];