From dd0a66ada0bd0ae6c96ea45cfa1581797e867a40 Mon Sep 17 00:00:00 2001 From: Dmitry Bogdanov Date: Thu, 28 Jul 2022 00:41:24 +0300 Subject: scsi: target: core: Fix race during ACL removal Under huge load there is a possibility of race condition in updating se_dev_entry object in ACL removal procedure: NIP [c0080000154093d0] transport_lookup_cmd_lun+0x1f8/0x3d0 [target_core_mod] LR [c00800001542ab34] target_submit_cmd_map_sgls+0x11c/0x300 [target_core_mod] Call Trace: target_submit_cmd_map_sgls+0x11c/0x300 [target_core_mod] target_submit_cmd+0x44/0x60 [target_core_mod] tcm_qla2xxx_handle_cmd+0x88/0xe0 [tcm_qla2xxx] qlt_do_work+0x2e4/0x3d0 [qla2xxx] process_one_work+0x298/0x5c Despite usage of RCU primitives with deve->se_lun pointer, it has not become dereference-safe because deve->se_lun is updated and not synchronized with a reader. That change might be in a release function called by synchronize_rcu(). But, in fact, there is no point in setting that pointer to NULL for deleting deve. All access to deve->se_lun is already under rcu_read_lock. And either deve->se_lun is always valid or deve is not valid itself and will not be found in the list_for_*. The same applicable for deve->se_lun_acl too. So a better solution is to remove that NULLing. Link: https://lore.kernel.org/r/20220727214125.19647-2-d.bogdanov@yadro.com Reviewed-by: Mike Christie Signed-off-by: Dmitry Bogdanov Signed-off-by: Martin K. Petersen --- drivers/target/target_core_device.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'drivers') diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c index 086ac9c9343c..88a844ae1fd0 100644 --- a/drivers/target/target_core_device.c +++ b/drivers/target/target_core_device.c @@ -434,9 +434,6 @@ void core_disable_device_list_for_node( kref_put(&orig->pr_kref, target_pr_kref_release); wait_for_completion(&orig->pr_comp); - rcu_assign_pointer(orig->se_lun, NULL); - rcu_assign_pointer(orig->se_lun_acl, NULL); - kfree_rcu(orig, rcu_head); core_scsi3_free_pr_reg_from_nacl(dev, nacl); -- cgit v1.2.3