fs/smb/server/server.c:283:5-24: WARNING: atomic_dec_and_test variation before object free at line 284.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8
commit: 9a8c5d89d327ff58e9b2517f8a6afb4181d32c6e ksmbd: fix use-after-free in SMB request handling
date:   3 weeks ago
config: parisc-randconfig-r053-20241215 (https://download.01.org/0day-ci/archive/20241216/202412161024.LgGt4s2G-lkp@xxxxxxxxx/config)
compiler: hppa-linux-gcc (GCC) 14.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412161024.LgGt4s2G-lkp@xxxxxxxxx/

cocci warnings: (new ones prefixed by >>)
>> fs/smb/server/server.c:283:5-24: WARNING: atomic_dec_and_test variation before object free at line 284.

vim +283 fs/smb/server/server.c

   255	
   256	/**
   257	 * handle_ksmbd_work() - process pending smb work requests
   258	 * @wk:	smb work containing request command buffer
   259	 *
   260	 * called by kworker threads to processing remaining smb work requests
   261	 */
   262	static void handle_ksmbd_work(struct work_struct *wk)
   263	{
   264		struct ksmbd_work *work = container_of(wk, struct ksmbd_work, work);
   265		struct ksmbd_conn *conn = work->conn;
   266	
   267		atomic64_inc(&conn->stats.request_served);
   268	
   269		__handle_ksmbd_work(work, conn);
   270	
   271		ksmbd_conn_try_dequeue_request(work);
   272		ksmbd_free_work_struct(work);
   273		atomic_dec(&conn->mux_smb_requests);
   274		/*
   275		 * Checking waitqueue to dropping pending requests on
   276		 * disconnection. waitqueue_active is safe because it
   277		 * uses atomic operation for condition.
   278		 */
   279		atomic_inc(&conn->refcnt);
   280		if (!atomic_dec_return(&conn->r_count) && waitqueue_active(&conn->r_count_q))
   281			wake_up(&conn->r_count_q);
   282	
 > 283		if (atomic_dec_and_test(&conn->refcnt))
 > 284			kfree(conn);
   285	}
   286	

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