From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maurizio Lombardi Date: Wed, 07 Oct 2020 14:53:26 +0000 Subject: [PATCH 2/2] target: iscsi: fix a race condition when aborting a task Message-Id: <20201007145326.56850-3-mlombard@redhat.com> List-Id: References: <20201007145326.56850-1-mlombard@redhat.com> In-Reply-To: <20201007145326.56850-1-mlombard@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: martin.petersen@oracle.com Cc: linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, bvanassche@acm.org, michael.christie@oracle.com Archived-At: List-Archive: List-Post: The iscsit_release_commands_from_conn() function does the following operations: 1) locks the cmd_lock spinlock 2) Scans the list of commands and sets the CMD_T_FABRIC_STOP flag 3) Releases the cmd_lock spinlock 4) Rescans the list again and clears the i_conn_node link of each command If an abort task timer is fired between 3) and 4), it will find the CMD_T_FABRIC_STOP flag set and won't call list_del_init(); therefore it may end up calling __iscsit_free_cmd() with a non-empty i_conn_node list, thus triggering the warning. Considering that: - we expect list_del_init() to be executed by iscsit_release_commands_from_conn() when the CMD_T_FABRIC_STOP is set. - iscsit_aborted_task() is the only function that calls __iscsit_free_cmd() directly, while all the other functions call iscsit_free_cmd(). - the warning in __iscsit_free_cmd() is a duplicate (the same warning can be found in iscsit_free_cmd(). We can fix the bug by simply removing the warning from __iscsit_free_cmd() kernel: ------------[ cut here ]------------ kernel: WARNING: CPU: 1 PID: 21173 at drivers/target/iscsi/iscsi_target_util.c:720 __iscsit_free_cmd+0x26e/0x290 [iscsi_target_mod] ... kernel: CPU: 1 PID: 21173 Comm: kworker/u8:3 Kdump: loaded Not tainted 3.10.0-1062.4.1.el7.x86_64 #1 kernel: Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 09/17/2015 kernel: Workqueue: tmr-user target_tmr_work [target_core_mod] kernel: Call Trace: kernel: [] dump_stack+0x19/0x1b kernel: [] __warn+0xd8/0x100 kernel: [] warn_slowpath_null+0x1d/0x20 kernel: [] __iscsit_free_cmd+0x26e/0x290 [iscsi_target_mod] kernel: [] iscsit_aborted_task+0x64/0x70 [iscsi_target_mod] kernel: [] lio_aborted_task+0x2a/0x30 [iscsi_target_mod] kernel: [] transport_cmd_finish_abort+0x66/0xb0 [target_core_mod] kernel: [] core_tmr_abort_task+0x102/0x180 [target_core_mod] kernel: [] target_tmr_work+0x152/0x170 [target_core_mod] kernel: [] process_one_work+0x17f/0x440 kernel: [] worker_thread+0x126/0x3c0 kernel: [] ? manage_workers.isra.26+0x2a0/0x2a0 kernel: [] kthread+0xd1/0xe0 kernel: [] ? insert_kthread_work+0x40/0x40 kernel: [] ret_from_fork_nospec_begin+0x21/0x21 kernel: [] ? insert_kthread_work+0x40/0x40 kernel: ---[ end trace ed2119501826ec7a ]--- Signed-off-by: Maurizio Lombardi --- drivers/target/iscsi/iscsi_target_util.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target_util.c b/drivers/target/iscsi/iscsi_target_util.c index 3082f5bde9fa..61233755ece0 100644 --- a/drivers/target/iscsi/iscsi_target_util.c +++ b/drivers/target/iscsi/iscsi_target_util.c @@ -741,8 +741,6 @@ void __iscsit_free_cmd(struct iscsi_cmd *cmd, bool check_queues) { struct iscsi_conn *conn = cmd->conn; - WARN_ON(!list_empty(&cmd->i_conn_node)); - if (cmd->data_direction = DMA_TO_DEVICE) { iscsit_stop_dataout_timer(cmd); iscsit_free_r2ts_from_list(cmd); -- 2.26.2