Messages in this thread | | | Date | Tue, 17 Apr 2018 11:19:57 +0200 | From | Oleksandr Natalenko <> | Subject | Re: usercopy whitelist woe in scsi_sense_cache |
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Hi.
17.04.2018 05:12, Kees Cook wrote: >> Turning off HARDENED_USERCOPY and turning on KASAN, I see the same >> report: >> >> [ 38.274106] BUG: KASAN: slab-out-of-bounds in >> _copy_to_user+0x42/0x60 >> [ 38.274841] Read of size 22 at addr ffff8800122b8c4b by task >> smartctl/1064 >> [ 38.275630] >> [ 38.275818] CPU: 2 PID: 1064 Comm: smartctl Not tainted >> 4.17.0-rc1-ARCH+ #266 >> [ 38.276631] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), >> BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 >> [ 38.277690] Call Trace: >> [ 38.277988] dump_stack+0x71/0xab >> [ 38.278397] ? _copy_to_user+0x42/0x60 >> [ 38.278833] print_address_description+0x6a/0x270 >> [ 38.279368] ? _copy_to_user+0x42/0x60 >> [ 38.279800] kasan_report+0x243/0x360 >> [ 38.280221] _copy_to_user+0x42/0x60 >> [ 38.280635] sg_io+0x459/0x660 >> ... >> >> Though we get slightly more details (some we already knew): >> >> [ 38.301330] Allocated by task 329: >> [ 38.301734] kmem_cache_alloc_node+0xca/0x220 >> [ 38.302239] scsi_mq_init_request+0x64/0x130 [scsi_mod] >> [ 38.302821] blk_mq_alloc_rqs+0x2cf/0x370 >> [ 38.303265] blk_mq_sched_alloc_tags.isra.4+0x7d/0xb0 >> [ 38.303820] blk_mq_init_sched+0xf0/0x220 >> [ 38.304268] elevator_switch+0x17a/0x2c0 >> [ 38.304705] elv_iosched_store+0x173/0x220 >> [ 38.305171] queue_attr_store+0x72/0xb0 >> [ 38.305602] kernfs_fop_write+0x188/0x220 >> [ 38.306049] __vfs_write+0xb6/0x330 >> [ 38.306436] vfs_write+0xe9/0x240 >> [ 38.306804] ksys_write+0x98/0x110 >> [ 38.307181] do_syscall_64+0x6d/0x1d0 >> [ 38.307590] entry_SYSCALL_64_after_hwframe+0x44/0xa9 >> [ 38.308142] >> [ 38.308316] Freed by task 0: >> [ 38.308652] (stack is not available) >> [ 38.309060] >> [ 38.309243] The buggy address belongs to the object at >> ffff8800122b8c00 >> [ 38.309243] which belongs to the cache scsi_sense_cache of size 96 >> [ 38.310625] The buggy address is located 75 bytes inside of >> [ 38.310625] 96-byte region [ffff8800122b8c00, ffff8800122b8c60) > > With a hardware watchpoint, I've isolated the corruption to here: > > bfq_dispatch_request+0x2be/0x1610: > __bfq_dispatch_request at block/bfq-iosched.c:3902 > 3900 if (rq) { > 3901 inc_in_driver_start_rq: > 3902 bfqd->rq_in_driver++; > 3903 start_rq: > 3904 rq->rq_flags |= RQF_STARTED; > 3905 } > > Through some race condition(?), rq_in_driver is also sense_buffer, and > it can get incremented. > … > I still haven't figured this out, though... any have a moment to look > at this?
By any chance, have you tried to simplify the reproducer environment, or it still needs my complex layout to trigger things even with KASAN?
Regards, Oleksandr
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