KASAN: use-after-free Read in relay_switch_subbuf

From: syzbot
Date: Wed Sep 26 2018 - 03:41:08 EST

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Hello,

syzbot found the following crash on:

HEAD commit: 2dd68cc7fd8c Merge gitolite.kernel.org:/pub/scm/linux/kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=105fe676400000
kernel config: https://syzkaller.appspot.com/x/.config?x=22a62640793a83c9
dashboard link: https://syzkaller.appspot.com/bug?extid=29093015c21333d1c46d
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+29093015c21333d1c46d@xxxxxxxxxxxxxxxxxxxxxxxxx

8021q: adding VLAN 0 to HW filter on device team0
device team0 left promiscuous mode
device team_slave_0 left promiscuous mode
device team_slave_1 left promiscuous mode
==================================================================
BUG: KASAN: use-after-free in relay_switch_subbuf+0xa0e/0xa70 kernel/relay.c:753
Read of size 8 at addr ffff8801b3c10778 by task kworker/0:3/5668

CPU: 0 PID: 5668 Comm: kworker/0:3 Not tainted 4.19.0-rc5+ #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events __blk_release_queue
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
relay_switch_subbuf+0xa0e/0xa70 kernel/relay.c:753
relay_flush+0x1c6/0x280 kernel/relay.c:881
__blk_trace_startstop.isra.20+0x2ae/0x8c0 kernel/trace/blktrace.c:668
blk_trace_shutdown+0x5b/0x80 kernel/trace/blktrace.c:751
__blk_release_queue+0x22d/0x500 block/blk-sysfs.c:852
process_one_work+0xc90/0x1b90 kernel/workqueue.c:2153
device team0 entered promiscuous mode
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
device team_slave_0 entered promiscuous mode
device team_slave_1 entered promiscuous mode
kthread+0x35a/0x420 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:413

Allocated by task 26646:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
8021q: adding VLAN 0 to HW filter on device team0
__d_alloc+0xc8/0xcc0 fs/dcache.c:1614
d_alloc+0x96/0x380 fs/dcache.c:1698
d_alloc_parallel+0x15a/0x1f40 fs/dcache.c:2441
__lookup_slow+0x1e6/0x540 fs/namei.c:1654
lookup_one_len+0x1d8/0x220 fs/namei.c:2543
start_creating+0xf2/0x220 fs/debugfs/inode.c:308
__debugfs_create_file+0x63/0x400 fs/debugfs/inode.c:347
debugfs_create_file+0x57/0x70 fs/debugfs/inode.c:399
blk_create_buf_file_callback+0x33/0x40 kernel/trace/blktrace.c:444
relay_create_buf_file+0xf6/0x150 kernel/relay.c:428
relay_open_buf.part.10+0x753/0xb20 kernel/relay.c:455
relay_open_buf kernel/relay.c:447 [inline]
relay_open+0x5e9/0xac0 kernel/relay.c:597
do_blk_trace_setup+0x4fb/0xda0 kernel/trace/blktrace.c:532
__blk_trace_setup+0xd5/0x180 kernel/trace/blktrace.c:577
blk_trace_ioctl+0x17a/0x2f0 kernel/trace/blktrace.c:716
blkdev_ioctl+0x8bc/0x2010 block/ioctl.c:587
block_ioctl+0xee/0x130 fs/block_dev.c:1883
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 26604:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x83/0x290 mm/slab.c:3756
__d_free+0x20/0x30 fs/dcache.c:257
__rcu_reclaim kernel/rcu/rcu.h:236 [inline]
rcu_do_batch kernel/rcu/tree.c:2576 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2880 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2847 [inline]
rcu_process_callbacks+0xf23/0x2670 kernel/rcu/tree.c:2864
__do_softirq+0x30b/0xad8 kernel/softirq.c:292

The buggy address belongs to the object at ffff8801b3c10720
which belongs to the cache dentry(81:syz1) of size 288
The buggy address is located 88 bytes inside of
288-byte region [ffff8801b3c10720, ffff8801b3c10840)
The buggy address belongs to the page:
page:ffffea0006cf0400 count:1 mapcount:0 mapping:ffff8801bb6ce300 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea00072adb88 ffffea0006800c48 ffff8801bb6ce300
raw: 0000000000000000 ffff8801b3c10040 000000010000000b ffff8801c7eb6100
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8801c7eb6100

Memory state around the buggy address:
ffff8801b3c10600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b3c10680: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc

ffff8801b3c10700: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb

^
ffff8801b3c10780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b3c10800: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================
kobject: 'loop1' (00000000f4503744): kobject_uevent_env
device team0 left promiscuous mode
kobject: 'loop1' (00000000f4503744): fill_kobj_path: path = '/devices/virtual/block/loop1'
device team_slave_0 left promiscuous mode
kobject: 'cpu0' (000000004fdcedbb): kobject_add_internal: parent: '0', set: '<NULL>'
device team_slave_1 left promiscuous mode
kobject: 'cpu1' (00000000e70df734): kobject_add_internal: parent: '0', set: '<NULL>'
kobject: 'kvm' (000000009a7db5f0): kobject_uevent_env
kobject: 'queue' (0000000084fcdfca): kobject_uevent_env
kobject: 'kvm' (000000009a7db5f0): fill_kobj_path: path = '/devices/virtual/misc/kvm'
kobject: 'queue' (0000000084fcdfca): kobject_uevent_env: filter function caused the event to drop!
device team0 entered promiscuous mode

---
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Next message: Nathan Chancellor: "Re: [PATCH] staging: rtl8723bs: Mark ACPI table declaration as maybe unused"
Previous message: syzbot: "WARNING in pfkey_sock_destruct"
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