syzbot


KASAN: use-after-free Read in iotlb_access_ok

Status: fixed on 2018/08/28 17:48
Subsystems: kvm net virt
[Documentation on labels]
Reported-by: syzbot+c51e6736a1bf614b3272@syzkaller.appspotmail.com
Fix commit: b13f9c636437 vhost: reset metadata cache when initializing new IOTLB
First crash: 2116d, last: 2116d
Discussions (4)
Title Replies (including bot) Last reply
[PATCH 4.14 00/29] 4.14.66-stable review 33 (33) 2018/08/21 19:49
[PATCH 4.17 00/42] 4.17.18-stable review 46 (46) 2018/08/21 19:44
[PATCH net] vhost: reset metadata cache when initializing new IOTLB 2 (2) 2018/08/08 16:45
KASAN: use-after-free Read in iotlb_access_ok 1 (2) 2018/08/08 02:52

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in vhost_vq_meta_fetch drivers/vhost/vhost.c:702 [inline]
BUG: KASAN: use-after-free in iotlb_access_ok+0x5c9/0x600 drivers/vhost/vhost.c:1177
Read of size 8 at addr ffff880197df2fc0 by task vhost-8938/8941

CPU: 0 PID: 8941 Comm: vhost-8938 Not tainted 4.18.0-rc7+ #174
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 vhost_vq_meta_fetch drivers/vhost/vhost.c:702 [inline]
 iotlb_access_ok+0x5c9/0x600 drivers/vhost/vhost.c:1177
 vq_iotlb_prefetch+0x10e/0x230 drivers/vhost/vhost.c:1214
 handle_rx+0x247/0x1f80 drivers/vhost/net.c:799
 handle_rx_net+0x19/0x20 drivers/vhost/net.c:934
 vhost_worker+0x283/0x490 drivers/vhost/vhost.c:360
 kthread+0x345/0x410 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 8938:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
 kmalloc include/linux/slab.h:513 [inline]
 vhost_new_umem_range+0xcb/0x7c0 drivers/vhost/vhost.c:911
 vhost_process_iotlb_msg drivers/vhost/vhost.c:1000 [inline]
 vhost_chr_write_iter+0xe53/0x1a00 drivers/vhost/vhost.c:1043
 vhost_net_chr_write_iter+0x59/0x70 drivers/vhost/net.c:1399
 call_write_iter include/linux/fs.h:1793 [inline]
 new_sync_write fs/read_write.c:474 [inline]
 __vfs_write+0x6c6/0x9f0 fs/read_write.c:487
 vfs_write+0x1f8/0x560 fs/read_write.c:549
 ksys_write+0x101/0x260 fs/read_write.c:598
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write fs/read_write.c:607 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:607
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8950:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kfree+0xd9/0x260 mm/slab.c:3813
 vhost_umem_free+0x944/0x14d0 drivers/vhost/vhost.c:576
 vhost_umem_clean+0x83/0xf0 drivers/vhost/vhost.c:588
 vhost_init_device_iotlb+0x1d7/0x290 drivers/vhost/vhost.c:1568
 vhost_net_set_features drivers/vhost/net.c:1292 [inline]
 vhost_net_ioctl+0xff3/0x1a80 drivers/vhost/net.c:1357
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:684
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
 __do_sys_ioctl fs/ioctl.c:708 [inline]
 __se_sys_ioctl fs/ioctl.c:706 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff880197df2f80
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 64 bytes inside of
 96-byte region [ffff880197df2f80, ffff880197df2fe0)
The buggy address belongs to the page:
page:ffffea00065f7c80 count:1 mapcount:0 mapping:ffff8801dac004c0 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea0007530148 ffffea000663b888 ffff8801dac004c0
raw: 0000000000000000 ffff880197df2000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880197df2e80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff880197df2f00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff880197df2f80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                                           ^
 ffff880197df3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff880197df3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/08/03 08:00 upstream e30cb13c5a09 5b7e23bb .config console log report ci-upstream-kasan-gce-root
* Struck through repros no longer work on HEAD.