On 13.01.21 03:45, Shin'ichiro Kawasaki wrote:
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
Fixes: a35129024e88 ("scsi: target: tcmu: Use priv pointer in se_cmd")
Cc: stable@xxxxxxxxxxxxxxx # v5.9+
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
Thank you for the fix.
Acked-by: Bodo Stroesser <bostroesser@xxxxxxxxx>
