cifs: Handle race conditions during rename

When rename is executed on directory which has files for which
close is deferred, then rename will fail with EACCES.

This patch will try to close all deferred files when EACCES is received
and retry rename on a directory.

Signed-off-by: Rohith Surabattula <rohiths@microsoft.com>
Cc: stable@vger.kernel.org # 5.13
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index b96b253..65f8a70 100644 (file)
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1625,7 +1625,7 @@ int cifs_unlink(struct inode *dir, struct dentry *dentry)
                goto unlink_out;
        }
 
-       cifs_close_all_deferred_files(tcon);
+       cifs_close_deferred_file(CIFS_I(inode));
        if (cap_unix(tcon->ses) && (CIFS_UNIX_POSIX_PATH_OPS_CAP &
                                le64_to_cpu(tcon->fsUnixInfo.Capability))) {
                rc = CIFSPOSIXDelFile(xid, tcon, full_path,
@@ -2084,6 +2084,7 @@ cifs_rename2(struct user_namespace *mnt_userns, struct inode *source_dir,
        FILE_UNIX_BASIC_INFO *info_buf_target;
        unsigned int xid;
        int rc, tmprc;
+       int retry_count = 0;
 
        if (flags & ~RENAME_NOREPLACE)
                return -EINVAL;
@@ -2113,10 +2114,24 @@ cifs_rename2(struct user_namespace *mnt_userns, struct inode *source_dir,
                goto cifs_rename_exit;
        }
 
-       cifs_close_all_deferred_files(tcon);
+       cifs_close_deferred_file(CIFS_I(d_inode(source_dentry)));
+       if (d_inode(target_dentry) != NULL)
+               cifs_close_deferred_file(CIFS_I(d_inode(target_dentry)));
+
        rc = cifs_do_rename(xid, source_dentry, from_name, target_dentry,
                            to_name);
 
+       if (rc == -EACCES) {
+               while (retry_count < 3) {
+                       cifs_close_all_deferred_files(tcon);
+                       rc = cifs_do_rename(xid, source_dentry, from_name, target_dentry,
+                                           to_name);
+                       if (rc != -EACCES)
+                               break;
+                       retry_count++;
+               }
+       }
+
        /*
         * No-replace is the natural behavior for CIFS, so skip unlink hacks.
         */

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index 844abeb..cdb1ec1 100644 (file)
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -723,13 +723,19 @@ void
 cifs_close_deferred_file(struct cifsInodeInfo *cifs_inode)
 {
        struct cifsFileInfo *cfile = NULL;
-       struct cifs_deferred_close *dclose;
+
+       if (cifs_inode == NULL)
+               return;
 
        list_for_each_entry(cfile, &cifs_inode->openFileList, flist) {
-               spin_lock(&cifs_inode->deferred_lock);
-               if (cifs_is_deferred_close(cfile, &dclose))
-                       mod_delayed_work(deferredclose_wq, &cfile->deferred, 0);
-               spin_unlock(&cifs_inode->deferred_lock);
+               if (delayed_work_pending(&cfile->deferred)) {
+                       /*
+                        * If there is no pending work, mod_delayed_work queues new work.
+                        * So, Increase the ref count to avoid use-after-free.
+                        */
+                       if (!mod_delayed_work(deferredclose_wq, &cfile->deferred, 0))
+                               cifsFileInfo_get(cfile);
+               }
        }
 }