Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  cifs: Fix busy dentry used after unmounting  Since commit 340cea84f691c ("cifs: open files should not hold ref on superblock"), cifs file only holds the dentry ref_cnt, the cifs file close work(cfile->deferred) could be executed after unmounting, which will trigger a warning in generic_shutdown_super:  BUG: Dentry 00000000a14a6845{i=c,n=file}  still in use (1) [unmount of  cifs cifs]  The detailed processs is:    process A           process B           kworker  fd = open(PATH)   vfs_open    file->__f_path = *path // dentry->d_lockref.count = 1    cifs_open     cifs_new_fileinfo      cfile->dentry = dget(dentry) // dentry->d_lockref.count = 2  close(fd)   __fput   cifs_close    queue_delayed_work(deferredclose_wq, cfile->deferred)   dput(dentry) // dentry->d_lockref.count = 1 			                 smb2_deferred_work_close 					  _cifsFileInfo_put 					   list_del(&cifs_file->flist)                     umount 		     cleanup_mnt 		      deactivate_super 		       cifs_kill_sb 		        cifs_close_all_deferred_files_sb 			 cifs_close_all_deferred_files 			  // cannot find cfile, skip _cifsFileInfo_put 			kill_anon_super 			 generic_shutdown_super 			  shrink_dcache_for_umount 			   umount_check 			    WARN ! // dentry->d_lockref.count = 1 					   cifsFileInfo_put_final 					    dput(cifs_file->dentry) 		                            // dentry->d_lockref.count = 0  Fix it by flushing 'deferredclose_wq' before calling kill_anon_super.  Fetch a reproducer in https://bugzilla.kernel.org/show_bug.cgi?id=221548.