Re: [PATCH] Avoid that scsi_exit_rq() triggers a use-after-free

Scott Bauer
2017-05-02T23:00:35Z

On Tue, May 02, 2017 at 10:43:30AM -0700, Bart Van Assche wrote:
> This patch fixes the following KASAN complaint:
>
> ==================================================================
> BUG: KASAN: use-after-free in scsi_exit_rq+0xf3/0x120 at addr ffff8802b7fedf00
> Read of size 1 by task rcuos/5/53
> CPU: 7 PID: 53 Comm: rcuos/6 Not tainted 4.11.0-rc5+ #13
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0 ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
> Call Trace:
> dump_stack+0x63/0x8f
> kasan_object_err+0x21/0x70
> kasan_report.part.1+0x231/0x500
> __asan_report_load1_noabort+0x2e/0x30
> scsi_exit_rq+0xf3/0x120
> free_request_size+0x44/0x60
> mempool_destroy.part.6+0x9b/0x150
> mempool_destroy+0x13/0x20
> blk_exit_rl+0x36/0x40
> blkg_free+0x146/0x200
> __blkg_release_rcu+0x121/0x220
> rcu_nocb_kthread+0x61f/0xca0
> kthread+0x298/0x390
> ret_from_fork+0x2c/0x40
> Object at ffff8802b7fedd80, in cache kmalloc-2048 size: 2048
> Allocated:
> PID = 3992
> save_stack_trace+0x1b/0x20
> save_stack+0x46/0xd0
> kasan_kmalloc+0xad/0xe0
> __kmalloc+0x134/0x220
> scsi_host_alloc+0x6b/0x11c0
> 0xffffffffc101d94a
> driver_probe_device+0x49e/0xc60
> __device_attach_driver+0x1d3/0x2a0
> bus_for_each_drv+0x11a/0x1d0
> __device_attach+0x1e1/0x2c0
> device_initial_probe+0x13/0x20
> bus_probe_device+0x19b/0x240
> device_add+0x86d/0x1450
> device_register+0x1a/0x20
> 0xffffffffc10270ce
> 0xffffffffc1048a62
> do_one_initcall+0xa7/0x250
> do_init_module+0x1d0/0x55d
> load_module+0x7c9f/0x9850
> SYSC_finit_module+0x189/0x1c0
> SyS_finit_module+0xe/0x10
> entry_SYSCALL_64_fastpath+0x1a/0xa9
> Freed:
> PID = 4128
> save_stack_trace+0x1b/0x20
> save_stack+0x46/0xd0
> kasan_slab_free+0x71/0xb0
> kfree+0x8d/0x1b0
> scsi_host_dev_release+0x2cb/0x430
> device_release+0x76/0x1e0
> kobject_release+0x107/0x370
> kobject_put+0x56/0xb0
> put_device+0x17/0x20
> scsi_host_put+0x15/0x20
> 0xffffffffc101fcd7
> device_release_driver_internal+0x26a/0x4e0
> device_release_driver+0x12/0x20
> bus_remove_device+0x2d0/0x590
> device_del+0x55b/0x920
> device_unregister+0x1a/0xa0
> 0xffffffffc101e0ca
> 0xffffffffc102fccc
> SyS_delete_module+0x334/0x3e0
> entry_SYSCALL_64_fastpath+0x1a/0xa9
> Memory state around the buggy address:
> ffff8802b7fede00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8802b7fede80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff8802b7fedf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff8802b7fedf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8802b7fee000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
> Reported-by: Scott Bauer <scott.bauer@intel.com>
> Fixes: e9c787e65c0c ("scsi: allocate scsi_cmnd structures as part of struct request")
> Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Scott Bauer <scott.bauer@intel.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Hannes Reinecke <hare@suse.com>
> Cc: <stable@vger.kernel.org>
> ---
> drivers/scsi/scsi_lib.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 15c9fe766071..d698364df072 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -2095,11 +2095,14 @@ static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
> struct Scsi_Host *shost = q->rq_alloc_data;
> struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
>
> + if (!scsi_host_get(shost))
> + goto fail;
> +
> memset(cmd, 0, sizeof(*cmd));
>
> cmd->sense_buffer = scsi_alloc_sense_buffer(shost, gfp, NUMA_NO_NODE);
> if (!cmd->sense_buffer)
> - goto fail;
> + goto put;
> cmd->req.sense = cmd->sense_buffer;
>
> if (scsi_host_get_prot(shost) >= SHOST_DIX_TYPE0_PROTECTION) {
> @@ -2112,6 +2115,8 @@ static int scsi_init_rq(struct request_queue *q, struct request *rq, gfp_t gfp)
>
> fail_free_sense:
> scsi_free_sense_buffer(shost, cmd->sense_buffer);
> +put:
> + scsi_host_put(shost);
> fail:
> return -ENOMEM;
> }
> @@ -2124,6 +2129,7 @@ static void scsi_exit_rq(struct request_queue *q, struct request *rq)
> if (cmd->prot_sdb)
> kmem_cache_free(scsi_sdb_cache, cmd->prot_sdb);
> scsi_free_sense_buffer(shost, cmd->sense_buffer);
> + scsi_host_put(shost);
> }
>
> struct request_queue *scsi_alloc_queue(struct scsi_device *sdev)
> --
> 2.12.2
>

I've applied this on-top of Jens' For-Linus and re-ran the test. I get the following scheduling
while atomic BUG() splat:

[ 30.686851] run fstests generic/108 at 2017-05-02 16:56:42
[ 30.953920] XFS (nvme1n1): Unmounting Filesystem
[ 31.020543] scsi host2: scsi_debug: version 1.86 [20160430]
[ 31.020543] dev_size_mb=128, opts=0x0, submit_queues=1, statistics=0
[ 31.022341] scsi 2:0:0:0: Direct-Access Linux scsi_debug 0186 PQ: 0 ANSI: 7
[ 31.074668] sd 2:0:0:0: Attached scsi generic sg1 type 0
[ 31.083077] sd 2:0:0:0: [sda] 262144 512-byte logical blocks: (134 MB/128 MiB)
[ 31.088168] sd 2:0:0:0: [sda] Write Protect is off
[ 31.088829] sd 2:0:0:0: [sda] Mode Sense: 73 00 10 08
[ 31.097875] sd 2:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[ 31.195672] sd 2:0:0:0: [sda] Attached SCSI disk
[ 34.039198] XFS (dm-0): Mounting V5 Filesystem
[ 34.066635] XFS (dm-0): Ending clean mount
[ 34.244127] sd 2:0:0:0: rejecting I/O to offline device
[ 34.244530] sd 2:0:0:0: rejecting I/O to offline device
[ 34.244991] sd 2:0:0:0: rejecting I/O to offline device
[ 34.245363] sd 2:0:0:0: rejecting I/O to offline device
[ 34.246094] sd 2:0:0:0: rejecting I/O to offline device
[ 34.246711] sd 2:0:0:0: rejecting I/O to offline device
[ 34.247336] sd 2:0:0:0: rejecting I/O to offline device
[ 34.247705] sd 2:0:0:0: rejecting I/O to offline device
[ 34.249195] sd 2:0:0:0: rejecting I/O to offline device
[ 34.249561] blk_update_request: I/O error, dev sda, sector 0
[ 34.286197] XFS (dm-0): Unmounting Filesystem
[ 35.672931] sd 2:0:0:0: [sda] Synchronizing SCSI cache
[ 35.753764] BUG: scheduling while atomic: swapper/0/0/0x00000100
[ 35.754333] Modules linked in: xfs binfmt_misc ppdev joydev input_leds serio_raw i2c_piix4 parport_pc parport mac_hid ib_iser rdma_cm iw_cm ib_cm ib_core configfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear psmouse nvme nvme_core pata_acpi floppy [last unloaded: scsi_debug]
[ 35.757226] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.11.0+ #1
[ 35.757708] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
[ 35.758462] Call Trace:
[ 35.758630] <IRQ>
[ 35.758783] dump_stack+0x63/0x82
[ 35.759017] __schedule_bug+0xe9/0x120
[ 35.759278] __schedule+0x126b/0x1c50
[ 35.759534] ? save_stack+0xb5/0xd0
[ 35.759772] ? pci_mmcfg_check_reserved+0x110/0x110
[ 35.760107] ? scsi_host_dev_release+0xb4/0x430
[ 35.760419] ? device_release+0x76/0x1e0
[ 35.760685] ? kobject_put+0x56/0xb0
[ 35.760930] ? scsi_host_put+0x15/0x20
[ 35.761185] ? scsi_exit_rq+0xe9/0x120
[ 35.761444] schedule+0x8d/0x1a0
[ 35.761675] schedule_timeout+0x557/0x8a0
[ 35.761958] ? flush_workqueue_prep_pwqs+0x2e8/0x400
[ 35.762303] ? cpu_startup_entry+0xcf/0xe0
[ 35.762587] ? usleep_range+0x120/0x120
[ 35.762862] ? kvm_sched_clock_read+0x1e/0x30
[ 35.763174] ? sched_clock+0x9/0x10
[ 35.763426] ? __x2apic_send_IPI_dest.constprop.4+0x31/0x40
[ 35.763820] ? x2apic_send_IPI+0x72/0xa0
[ 35.764097] wait_for_completion+0x1ae/0x310
[ 35.764396] ? wait_for_completion+0x1ae/0x310
[ 35.764707] ? bit_wait_io_timeout+0x130/0x130
[ 35.765018] ? wake_up_q+0xe0/0xe0
[ 35.765264] kthread_stop+0xa1/0x300
[ 35.765522] destroy_workqueue+0x2db/0x560
[ 35.765844] scsi_host_dev_release+0xe7/0x430
[ 35.766155] device_release+0x76/0x1e0
[ 35.766425] kobject_release+0x107/0x370
[ 35.766706] kobject_put+0x56/0xb0
[ 35.766962] put_device+0x17/0x20
[ 35.767201] scsi_host_put+0x15/0x20
[ 35.767457] scsi_exit_rq+0xe9/0x120
[ 35.767720] free_request_size+0x44/0x60
[ 35.768008] mempool_destroy.part.6+0x9b/0x150
[ 35.768326] ? kasan_slab_free+0x87/0xb0
[ 35.768607] mempool_destroy+0x13/0x20
[ 35.768879] blk_exit_rl+0x36/0x40
[ 35.769121] blkg_free+0xcd/0x190
[ 35.769349] __blkg_release_rcu+0x121/0x220
[ 35.769636] rcu_process_callbacks+0x831/0xfb0
[ 35.769947] __do_softirq+0x1a9/0x558
[ 35.770199] irq_exit+0x14e/0x180
[ 35.770424] smp_apic_timer_interrupt+0x7b/0xa0
[ 35.770732] apic_timer_interrupt+0x89/0x90
[ 35.771021] RIP: 0010:native_safe_halt+0x6/0x10
[ 35.771328] RSP: 0018:ffffffffa7407d08 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
[ 35.771843] RAX: 0000000000000000 RBX: ffffffffa7416d80 RCX: 0000000000000000
[ 35.772342] RDX: 1ffffffff4e82db0 RSI: 0000000000000000 RDI: 0000000000000000
[ 35.772832] RBP: ffffffffa7407d08 R08: 000000084fa5bc00 R09: 00000000fffefde4
[ 35.773306] R10: ffff880333fec010 R11: 000005e17de691b5 R12: ffffffffa7416d80
[ 35.773793] R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
[ 35.774287] </IRQ>
[ 35.774484] default_idle+0x22/0x210
[ 35.774738] arch_cpu_idle+0xf/0x20
[ 35.774992] default_idle_call+0x3b/0x60
[ 35.775273] do_idle+0x1fd/0x2d0
[ 35.775515] cpu_startup_entry+0xcf/0xe0
[ 35.775798] ? cpu_in_idle+0x20/0x20
[ 35.776056] rest_init+0x9e/0xb0
[ 35.776300] start_kernel+0x691/0x6cd
[ 35.776564] ? thread_stack_cache_init+0x6/0x6
[ 35.776881] ? early_idt_handler_array+0x120/0x120
[ 35.777222] x86_64_start_reservations+0x24/0x26
[ 35.777551] x86_64_start_kernel+0x148/0x16b
[ 35.777866] start_cpu+0x14/0x14
[ 35.778259] bad: scheduling from the idle thread!
[ 35.778852] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 4.11.0+ #1
[ 35.779622] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014
[ 35.780437] Call Trace:
[ 35.780658] <IRQ>
[ 35.780847] dump_stack+0x63/0x82
[ 35.781143] dequeue_task_idle+0x2c/0x40
[ 35.781516] deactivate_task+0x125/0x2e0
[ 35.781936] __schedule+0x9d4/0x1c50
[ 35.782214] ? pci_mmcfg_check_reserved+0x110/0x110
[ 35.782652] ? __switch_to+0x639/0xd30
[ 35.782984] schedule+0x8d/0x1a0
[ 35.783236] schedule_timeout+0x557/0x8a0
[ 35.783620] ? usleep_range+0x120/0x120
[ 35.783937] ? pci_mmcfg_check_reserved+0x110/0x110
[ 35.784345] ? sched_clock+0x9/0x10
[ 35.784638] ? x2apic_send_IPI+0x72/0xa0
[ 35.785147] wait_for_completion+0x1ae/0x310
[ 35.785876] ? wait_for_completion+0x1ae/0x310
[ 35.786314] ? bit_wait_io_timeout+0x130/0x130
[ 35.786641] ? wake_up_q+0xe0/0xe0
[ 35.786900] ? put_pwq+0xa6/0xf0
[ 35.787141] kthread_stop+0xa1/0x300
[ 35.787405] scsi_host_dev_release+0x114/0x430
[ 35.787729] device_release+0x76/0x1e0
[ 35.788004] kobject_release+0x107/0x370
[ 35.788291] kobject_put+0x56/0xb0
[ 35.788540] put_device+0x17/0x20
[ 35.788786] scsi_host_put+0x15/0x20
[ 35.789048] scsi_exit_rq+0xe9/0x120
[ 35.789311] free_request_size+0x44/0x60
[ 35.789598] mempool_destroy.part.6+0x9b/0x150
[ 35.789945] ? kasan_slab_free+0x87/0xb0
[ 35.790237] mempool_destroy+0x13/0x20
[ 35.790515] blk_exit_rl+0x36/0x40
[ 35.790763] blkg_free+0xcd/0x190
[ 35.791011] __blkg_release_rcu+0x121/0x220
[ 35.791412] rcu_process_callbacks+0x831/0xfb0
[ 35.791997] __do_softirq+0x1a9/0x558
[ 35.792551] irq_exit+0x14e/0x180
[ 35.793006] smp_apic_timer_interrupt+0x7b/0xa0
[ 35.793655] apic_timer_interrupt+0x89/0x90
[ 35.794128] RIP: 0010:native_safe_halt+0x6/0x10
[ 35.794461] RSP: 0018:ffffffffa7407d08 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff10
[ 35.795015] RAX: 0000000000000000 RBX: ffffffffa7416d80 RCX: 0000000000000000
[ 35.795525] RDX: 1ffffffff4e82db0 RSI: 0000000000000000 RDI: 0000000000000000
[ 35.796036] RBP: ffffffffa7407d08 R08: 000000084fa5bc00 R09: 00000000fffefde4
[ 35.796549] R10: ffff880333fec010 R11: 000005e17de691b5 R12: ffffffffa7416d80
[ 35.797060] R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
[ 35.797573] </IRQ>
[ 35.797766] default_idle+0x22/0x210
[ 35.798027] arch_cpu_idle+0xf/0x20
[ 35.798278] default_idle_call+0x3b/0x60
[ 35.798560] do_idle+0x1fd/0x2d0
[ 35.798798] cpu_startup_entry+0xcf/0xe0
[ 35.799076] ? cpu_in_idle+0x20/0x20
[ 35.799335] rest_init+0x9e/0xb0
[ 35.799586] start_kernel+0x691/0x6cd
[ 35.799865] ? thread_stack_cache_init+0x6/0x6
[ 35.800221] ? early_idt_handler_array+0x120/0x120
[ 35.800601] x86_64_start_reservations+0x24/0x26
[ 35.800939] x86_64_start_kernel+0x148/0x16b
[ 35.801259] start_cpu+0x14/0x14
[ 35.801634] softirq: huh, entered softirq 9 RCU ffffffffa52a7600 with preempt_count 00000100, exited with 00000000?
[ 35.802651] ------------[ cut here ]------------