Re: KASAN: use-after-free Read in __list_add_valid (3)

[Eric Biggers]

On Wed, Jan 24, 2018 at 11:57:01PM -0800, syzbot wrote:
> Hello,
> 
> syzbot hit the following crash on upstream commit
> 1f07476ec143bbed7bf0b641749783b1094b4c4f (Tue Jan 23 20:45:40 2018 +0000)
> Merge tag 'pci-v4.15-fixes-3' of
> git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
> 
> So far this crash happened 6 times on upstream.
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+fbbedb95ed1d1e95781e@xxxxxxxxxxxxxxxxxxxxxxxxx
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> ==================================================================
> BUG: KASAN: use-after-free in __list_add_valid+0xb1/0xd0 lib/list_debug.c:23
> Read of size 8 at addr ffff8801bb5893d0 by task syz-executor1/28911
> 
> CPU: 0 PID: 28911 Comm: syz-executor1 Not tainted 4.15.0-rc9+ #277
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>  print_address_description+0x73/0x250 mm/kasan/report.c:252
>  kasan_report_error mm/kasan/report.c:351 [inline]
>  kasan_report+0x25b/0x340 mm/kasan/report.c:409
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
>  __list_add_valid+0xb1/0xd0 lib/list_debug.c:23
>  __list_add include/linux/list.h:60 [inline]
>  list_add include/linux/list.h:79 [inline]
>  __add_wait_queue include/linux/wait.h:156 [inline]
>  add_wait_queue+0xcf/0x290 kernel/sched/wait.c:30
>  vhost_poll_func+0x3d/0x50 drivers/vhost/vhost.c:165
>  poll_wait include/linux/poll.h:46 [inline]
>  eventfd_poll+0xe8/0x1f0 fs/eventfd.c:123
>  vhost_poll_start+0x97/0x1c0 drivers/vhost/vhost.c:212
>  vhost_vring_ioctl+0xe28/0x19b0 drivers/vhost/vhost.c:1556
>  vhost_net_ioctl+0x9df/0x1910 drivers/vhost/net.c:1320
>  vfs_ioctl fs/ioctl.c:46 [inline]
>  do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
>  SYSC_ioctl fs/ioctl.c:701 [inline]
>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>  entry_SYSCALL_64_fastpath+0x29/0xa0
> RIP: 0033:0x452f19
> RSP: 002b:00007f33da20dc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 00007f33da20e700 RCX: 0000000000452f19
> RDX: 00000000208ffff8 RSI: 000000004008af20 RDI: 0000000000000017
> RBP: 0000000000a2f850 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
> R13: 0000000000a2f7cf R14: 00007f33da20e9c0 R15: 0000000000000006
> 
> Allocated by task 28878:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
>  __do_kmalloc_node mm/slab.c:3672 [inline]
>  __kmalloc_node+0x47/0x70 mm/slab.c:3679
>  kmalloc_node include/linux/slab.h:541 [inline]
>  kvmalloc_node+0x64/0xd0 mm/util.c:397
>  kvmalloc include/linux/mm.h:541 [inline]
>  vhost_net_open+0x27/0x670 drivers/vhost/net.c:902
>  misc_open+0x382/0x500 drivers/char/misc.c:154
>  chrdev_open+0x257/0x730 fs/char_dev.c:417
>  do_dentry_open+0x667/0xd40 fs/open.c:752
>  vfs_open+0x107/0x220 fs/open.c:866
>  do_last fs/namei.c:3379 [inline]
>  path_openat+0x1151/0x3530 fs/namei.c:3519
>  do_filp_open+0x25b/0x3b0 fs/namei.c:3554
>  do_sys_open+0x502/0x6d0 fs/open.c:1059
>  SYSC_openat fs/open.c:1086 [inline]
>  SyS_openat+0x30/0x40 fs/open.c:1080
>  entry_SYSCALL_64_fastpath+0x29/0xa0
> 
> Freed by task 28878:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
>  __cache_free mm/slab.c:3488 [inline]
>  kfree+0xd6/0x260 mm/slab.c:3803
>  kvfree+0x36/0x60 mm/util.c:416
>  vhost_net_release+0x159/0x190 drivers/vhost/net.c:1012
>  __fput+0x327/0x7e0 fs/file_table.c:210
>  ____fput+0x15/0x20 fs/file_table.c:244
>  task_work_run+0x199/0x270 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>  exit_to_usermode_loop+0x296/0x310 arch/x86/entry/common.c:162
>  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
>  syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
>  entry_SYSCALL_64_fastpath+0x9e/0xa0
> 
> The buggy address belongs to the object at ffff8801bb589140
>  which belongs to the cache kmalloc-65536 of size 65536
> The buggy address is located 656 bytes inside of
>  65536-byte region [ffff8801bb589140, ffff8801bb599140)
> The buggy address belongs to the page:
> page:ffffea0006ed6000 count:1 mapcount:0 mapping:ffff8801bb589140 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffff8801bb589140 0000000000000000 0000000100000001
> raw: ffffea00068b0820 ffffea000693d020 ffff8801dac02500 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8801bb589280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801bb589300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff8801bb589380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                  ^
>  ffff8801bb589400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801bb589480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title

No reproducer for this one but I assume it was yet another report of the
vhost_net bug fixed by commit 4cd879515d68:

#syz fix: vhost_net: stop device during reset owner

- Eric