From: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx> commit 780e1384687d6ecdee9ca789a1027610484ac8a2 upstream. Commit a35129024e88 ("scsi: target: tcmu: Use priv pointer in se_cmd") modified tcmu_free_cmd() to set NULL to priv pointer in se_cmd. However, se_cmd can be already freed by work queue triggered in target_complete_cmd(). This caused BUG KASAN use-after-free [1]. To fix the bug, do not touch priv pointer in tcmu_free_cmd(). Instead, set NULL to priv pointer before target_complete_cmd() calls. Also, to avoid unnecessary priv pointer change in tcmu_queue_cmd(), modify priv pointer in the function only when tcmu_free_cmd() is not called. [1] BUG: KASAN: use-after-free in tcmu_handle_completions+0x1172/0x1770 [target_core_user] Write of size 8 at addr ffff88814cf79a40 by task cmdproc-uio0/14842 CPU: 2 PID: 14842 Comm: cmdproc-uio0 Not tainted 5.11.0-rc2 #1 Hardware name: Supermicro Super Server/X10SRL-F, BIOS 3.2 11/22/2019 Call Trace: dump_stack+0x9a/0xcc ? tcmu_handle_completions+0x1172/0x1770 [target_core_user] print_address_description.constprop.0+0x18/0x130 ? tcmu_handle_completions+0x1172/0x1770 [target_core_user] ? tcmu_handle_completions+0x1172/0x1770 [target_core_user] kasan_report.cold+0x7f/0x10e ? tcmu_handle_completions+0x1172/0x1770 [target_core_user] tcmu_handle_completions+0x1172/0x1770 [target_core_user] ? queue_tmr_ring+0x5d0/0x5d0 [target_core_user] tcmu_irqcontrol+0x28/0x60 [target_core_user] uio_write+0x155/0x230 ? uio_vma_fault+0x460/0x460 ? security_file_permission+0x4f/0x440 vfs_write+0x1ce/0x860 ksys_write+0xe9/0x1b0 ? __ia32_sys_read+0xb0/0xb0 ? syscall_enter_from_user_mode+0x27/0x70 ? trace_hardirqs_on+0x1c/0x110 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fcf8b61905f Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 b9 fc ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 0c fd ff ff 48 RSP: 002b:00007fcf7b3e6c30 EFLAGS: 00000293 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fcf8b61905f RDX: 0000000000000004 RSI: 00007fcf7b3e6c78 RDI: 000000000000000c RBP: 00007fcf7b3e6c80 R08: 0000000000000000 R09: 00007fcf7b3e6aa8 R10: 000000000b01c000 R11: 0000000000000293 R12: 00007ffe0c32a52e R13: 00007ffe0c32a52f R14: 0000000000000000 R15: 00007fcf7b3e7640 Allocated by task 383: kasan_save_stack+0x1b/0x40 ____kasan_kmalloc.constprop.0+0x84/0xa0 kmem_cache_alloc+0x142/0x330 tcm_loop_queuecommand+0x2a/0x4e0 [tcm_loop] scsi_queue_rq+0x12ec/0x2d20 blk_mq_dispatch_rq_list+0x30a/0x1db0 __blk_mq_do_dispatch_sched+0x326/0x830 __blk_mq_sched_dispatch_requests+0x2c8/0x3f0 blk_mq_sched_dispatch_requests+0xca/0x120 __blk_mq_run_hw_queue+0x93/0xe0 process_one_work+0x7b6/0x1290 worker_thread+0x590/0xf80 kthread+0x362/0x430 ret_from_fork+0x22/0x30 Freed by task 11655: kasan_save_stack+0x1b/0x40 kasan_set_track+0x1c/0x30 kasan_set_free_info+0x20/0x30 ____kasan_slab_free+0xec/0x120 slab_free_freelist_hook+0x53/0x160 kmem_cache_free+0xf4/0x5c0 target_release_cmd_kref+0x3ea/0x9e0 [target_core_mod] transport_generic_free_cmd+0x28b/0x2f0 [target_core_mod] target_complete_ok_work+0x250/0xac0 [target_core_mod] process_one_work+0x7b6/0x1290 worker_thread+0x590/0xf80 kthread+0x362/0x430 ret_from_fork+0x22/0x30 Last potentially related work creation: kasan_save_stack+0x1b/0x40 kasan_record_aux_stack+0xa3/0xb0 insert_work+0x48/0x2e0 __queue_work+0x4e8/0xdf0 queue_work_on+0x78/0x80 tcmu_handle_completions+0xad0/0x1770 [target_core_user] tcmu_irqcontrol+0x28/0x60 [target_core_user] uio_write+0x155/0x230 vfs_write+0x1ce/0x860 ksys_write+0xe9/0x1b0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Second to last potentially related work creation: kasan_save_stack+0x1b/0x40 kasan_record_aux_stack+0xa3/0xb0 insert_work+0x48/0x2e0 __queue_work+0x4e8/0xdf0 queue_work_on+0x78/0x80 tcm_loop_queuecommand+0x1c3/0x4e0 [tcm_loop] scsi_queue_rq+0x12ec/0x2d20 blk_mq_dispatch_rq_list+0x30a/0x1db0 __blk_mq_do_dispatch_sched+0x326/0x830 __blk_mq_sched_dispatch_requests+0x2c8/0x3f0 blk_mq_sched_dispatch_requests+0xca/0x120 __blk_mq_run_hw_queue+0x93/0xe0 process_one_work+0x7b6/0x1290 worker_thread+0x590/0xf80 kthread+0x362/0x430 ret_from_fork+0x22/0x30 The buggy address belongs to the object at ffff88814cf79800 which belongs to the cache tcm_loop_cmd_cache of size 896. Link: https://lore.kernel.org/r/20210113024508.1264992-1-shinichiro.kawasaki@xxxxxxx Fixes: a35129024e88 ("scsi: target: tcmu: Use priv pointer in se_cmd") Cc: stable@xxxxxxxxxxxxxxx # v5.9+ Acked-by: Bodo Stroesser <bostroesser@xxxxxxxxx> Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/target/target_core_user.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/drivers/target/target_core_user.c +++ b/drivers/target/target_core_user.c @@ -562,8 +562,6 @@ tcmu_get_block_page(struct tcmu_dev *ude static inline void tcmu_free_cmd(struct tcmu_cmd *tcmu_cmd) { - if (tcmu_cmd->se_cmd) - tcmu_cmd->se_cmd->priv = NULL; kfree(tcmu_cmd->dbi); kmem_cache_free(tcmu_cmd_cache, tcmu_cmd); } @@ -1188,11 +1186,12 @@ tcmu_queue_cmd(struct se_cmd *se_cmd) return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE; mutex_lock(&udev->cmdr_lock); - se_cmd->priv = tcmu_cmd; if (!(se_cmd->transport_state & CMD_T_ABORTED)) ret = queue_cmd_ring(tcmu_cmd, &scsi_ret); if (ret < 0) tcmu_free_cmd(tcmu_cmd); + else + se_cmd->priv = tcmu_cmd; mutex_unlock(&udev->cmdr_lock); return scsi_ret; } @@ -1255,6 +1254,7 @@ tcmu_tmr_notify(struct se_device *se_dev list_del_init(&cmd->queue_entry); tcmu_free_cmd(cmd); + se_cmd->priv = NULL; target_complete_cmd(se_cmd, SAM_STAT_TASK_ABORTED); unqueued = true; } @@ -1346,6 +1346,7 @@ static void tcmu_handle_completion(struc } done: + se_cmd->priv = NULL; if (read_len_valid) { pr_debug("read_len = %d\n", read_len); target_complete_cmd_with_length(cmd->se_cmd, @@ -1492,6 +1493,7 @@ static void tcmu_check_expired_queue_cmd se_cmd = cmd->se_cmd; tcmu_free_cmd(cmd); + se_cmd->priv = NULL; target_complete_cmd(se_cmd, SAM_STAT_TASK_SET_FULL); } @@ -1606,6 +1608,7 @@ static void run_qfull_queue(struct tcmu_ * removed then LIO core will do the right thing and * fail the retry. */ + tcmu_cmd->se_cmd->priv = NULL; target_complete_cmd(tcmu_cmd->se_cmd, SAM_STAT_BUSY); tcmu_free_cmd(tcmu_cmd); continue; @@ -1619,6 +1622,7 @@ static void run_qfull_queue(struct tcmu_ * Ignore scsi_ret for now. target_complete_cmd * drops it. */ + tcmu_cmd->se_cmd->priv = NULL; target_complete_cmd(tcmu_cmd->se_cmd, SAM_STAT_CHECK_CONDITION); tcmu_free_cmd(tcmu_cmd); @@ -2226,6 +2230,7 @@ static void tcmu_reset_ring(struct tcmu_ if (!test_bit(TCMU_CMD_BIT_EXPIRED, &cmd->flags)) { WARN_ON(!cmd->se_cmd); list_del_init(&cmd->queue_entry); + cmd->se_cmd->priv = NULL; if (err_level == 1) { /* * Userspace was not able to start the