Date:   Tue, 1 Feb 2022 08:50:49 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+476bd1c816c8c9c340d7@...kaller.appspotmail.com>
Cc:     axboe@...nel.dk, josef@...icpanda.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, nbd@...er.debian.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Read in recv_work (2)

On Tue, 1 Feb 2022 at 08:48, syzbot
<syzbot+476bd1c816c8c9c340d7@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    0280e3c58f92 Merge tag 'nfs-for-5.17-1' of git://git.linux..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11b3dde4700000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=916d34c0d501b86
> dashboard link: https://syzkaller.appspot.com/bug?extid=476bd1c816c8c9c340d7
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+476bd1c816c8c9c340d7@...kaller.appspotmail.com

There seems to be something with stacks reported by KASAN. The older
report looked more consistent (matching stacks):
https://syzkaller.appspot.com/bug?id=a2ca32319e8cd0cf8688611b1b69de781796d44e
but looks like the same problem(?)


BUG: KASAN: use-after-free in recv_work+0x2a2/0x2c0 drivers/block/nbd.c:787
Read of size 8 at addr ffff88801181ed20 by task kworker/u5:2/8465

CPU: 1 PID: 8465 Comm: kworker/u5:2 Not tainted
5.11.0-rc5-next-20210129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011
Workqueue: knbd5-recv recv_work
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:232
 __kasan_report mm/kasan/report.c:399 [inline]
 kasan_report.cold+0x7c/0xd8 mm/kasan/report.c:416
 recv_work+0x2a2/0x2c0 drivers/block/nbd.c:787
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Allocated by task 17044:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:403 [inline]
 ____kasan_kmalloc mm/kasan/common.c:434 [inline]
 ____kasan_kmalloc.constprop.0+0xa0/0xd0 mm/kasan/common.c:406
 kasan_slab_alloc include/linux/kasan.h:208 [inline]
 slab_post_alloc_hook mm/slab.h:516 [inline]
 slab_alloc_node mm/slub.c:2907 [inline]
 slab_alloc mm/slub.c:2915 [inline]
 __kmalloc_track_caller+0x16c/0x2e0 mm/slub.c:4550
 __do_krealloc mm/slab_common.c:1149 [inline]
 krealloc+0x60/0xa0 mm/slab_common.c:1178
 nbd_add_socket+0x263/0x6a0 drivers/block/nbd.c:1044
 __nbd_ioctl drivers/block/nbd.c:1369 [inline]
 nbd_ioctl+0x388/0xa50 drivers/block/nbd.c:1425
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:576
 block_ioctl+0xf9/0x140 fs/block_dev.c:1650
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 17044:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:357
 ____kasan_slab_free.part.0+0xe1/0x110 mm/kasan/common.c:364
 kasan_slab_free include/linux/kasan.h:191 [inline]
 slab_free_hook mm/slub.c:1562 [inline]
 slab_free_freelist_hook+0x82/0x1d0 mm/slub.c:1600
 slab_free mm/slub.c:3161 [inline]
 kfree+0xe5/0x7b0 mm/slub.c:4202
 krealloc+0x45/0xa0 mm/slab_common.c:1180
 nbd_add_socket+0x263/0x6a0 drivers/block/nbd.c:1044
 __nbd_ioctl drivers/block/nbd.c:1369 [inline]
 nbd_ioctl+0x388/0xa50 drivers/block/nbd.c:1425
 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:576
 block_ioctl+0xf9/0x140 fs/block_dev.c:1650
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9




> ==================================================================
> BUG: KASAN: use-after-free in recv_work+0x840/0x8b0 drivers/block/nbd.c:863
> Read of size 8 at addr ffff88801886e9b0 by task kworker/u5:5/3653
>
> CPU: 0 PID: 3653 Comm: kworker/u5:5 Not tainted 5.17.0-rc1-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Workqueue: nbd1-recv recv_work
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>  print_address_description.constprop.0.cold+0x8d/0x336 mm/kasan/report.c:255
>  __kasan_report mm/kasan/report.c:442 [inline]
>  kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
>  recv_work+0x840/0x8b0 drivers/block/nbd.c:863
>  process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
>  worker_thread+0x657/0x1110 kernel/workqueue.c:2454
>  kthread+0x2e9/0x3a0 kernel/kthread.c:377
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>  </TASK>
>
> Allocated by task 7763:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:45 [inline]
>  set_alloc_info mm/kasan/common.c:436 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:515 [inline]
>  ____kasan_kmalloc mm/kasan/common.c:474 [inline]
>  __kasan_kmalloc+0xa9/0xd0 mm/kasan/common.c:524
>  kmalloc_node include/linux/slab.h:604 [inline]
>  __vmalloc_area_node mm/vmalloc.c:2948 [inline]
>  __vmalloc_node_range+0x444/0x1060 mm/vmalloc.c:3107
>  __vmalloc_node mm/vmalloc.c:3157 [inline]
>  vzalloc+0x67/0x80 mm/vmalloc.c:3227
>  do_ipt_get_ctl+0x60d/0x9d0 net/ipv4/netfilter/ip_tables.c:801
>  nf_getsockopt+0x72/0xd0 net/netfilter/nf_sockopt.c:116
>  ip_getsockopt net/ipv4/ip_sockglue.c:1786 [inline]
>  ip_getsockopt+0x164/0x1c0 net/ipv4/ip_sockglue.c:1765
>  tcp_getsockopt+0x86/0xd0 net/ipv4/tcp.c:4284
>  __sys_getsockopt+0x21f/0x5f0 net/socket.c:2224
>  __do_sys_getsockopt net/socket.c:2239 [inline]
>  __se_sys_getsockopt net/socket.c:2236 [inline]
>  __x64_sys_getsockopt+0xba/0x150 net/socket.c:2236
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> Freed by task 29418:
>  kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x21/0x30 mm/kasan/common.c:45
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
>  ____kasan_slab_free mm/kasan/common.c:366 [inline]
>  ____kasan_slab_free+0x130/0x160 mm/kasan/common.c:328
>  kasan_slab_free include/linux/kasan.h:236 [inline]
>  slab_free_hook mm/slub.c:1728 [inline]
>  slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1754
>  slab_free mm/slub.c:3509 [inline]
>  kfree+0xcb/0x280 mm/slub.c:4562
>  krealloc+0x69/0xf0 mm/slab_common.c:1219
>  nbd_add_socket+0x2cb/0x810 drivers/block/nbd.c:1130
>  __nbd_ioctl drivers/block/nbd.c:1454 [inline]
>  nbd_ioctl+0x38c/0xb10 drivers/block/nbd.c:1511
>  blkdev_ioctl+0x37a/0x800 block/ioctl.c:588
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:874 [inline]
>  __se_sys_ioctl fs/ioctl.c:860 [inline]
>  __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The buggy address belongs to the object at ffff88801886e9b0
>  which belongs to the cache kmalloc-8 of size 8
> The buggy address is located 0 bytes inside of
>  8-byte region [ffff88801886e9b0, ffff88801886e9b8)
> The buggy address belongs to the page:
> page:ffffea0000621b80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1886e
> flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
> raw: 00fff00000000200 ffffea0001d57400 dead000000000002 ffff888010c41280
> raw: 0000000000000000 0000000080660066 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> page_owner tracks the page as allocated
> page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY), pid 3634, ts 181715914950, free_ts 181667651758
>  prep_new_page mm/page_alloc.c:2434 [inline]
>  get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
>  __alloc_pages+0x1b2/0x500 mm/page_alloc.c:5389
>  alloc_pages+0x1aa/0x310 mm/mempolicy.c:2271
>  alloc_slab_page mm/slub.c:1799 [inline]
>  allocate_slab mm/slub.c:1944 [inline]
>  new_slab+0x28a/0x3b0 mm/slub.c:2004
>  ___slab_alloc+0x87c/0xe90 mm/slub.c:3018
>  __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3105
>  slab_alloc_node mm/slub.c:3196 [inline]
>  slab_alloc mm/slub.c:3238 [inline]
>  __kmalloc+0x2fb/0x340 mm/slub.c:4420
>  kmalloc_array include/linux/slab.h:621 [inline]
>  kcalloc include/linux/slab.h:652 [inline]
>  nsim_fib6_event_init drivers/net/netdevsim/fib.c:807 [inline]
>  nsim_fib6_prepare_event drivers/net/netdevsim/fib.c:940 [inline]
>  nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:991 [inline]
>  nsim_fib_event_nb+0x2f1/0xc50 drivers/net/netdevsim/fib.c:1028
>  call_fib_notifier+0x32/0x70 net/core/fib_notifier.c:24
>  call_fib6_entry_notifier net/ipv6/ip6_fib.c:373 [inline]
>  fib6_rt_dump net/ipv6/ip6_fib.c:452 [inline]
>  fib6_node_dump+0x1c4/0x2d0 net/ipv6/ip6_fib.c:462
>  fib6_walk_continue+0x3e9/0x6c0 net/ipv6/ip6_fib.c:2112
>  fib6_walk+0x182/0x370 net/ipv6/ip6_fib.c:2160
>  fib6_table_dump net/ipv6/ip6_fib.c:474 [inline]
>  fib6_tables_dump+0x1dc/0x340 net/ipv6/ip6_fib.c:503
>  fib6_dump+0x47/0x60 net/ipv6/fib6_notifier.c:39
>  fib_net_dump net/core/fib_notifier.c:71 [inline]
>  register_fib_notifier+0x1fc/0x7b0 net/core/fib_notifier.c:109
>  nsim_fib_create+0x7a5/0xa60 drivers/net/netdevsim/fib.c:1557
> page last free stack trace:
>  reset_page_owner include/linux/page_owner.h:24 [inline]
>  free_pages_prepare mm/page_alloc.c:1352 [inline]
>  free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404
>  free_unref_page_prepare mm/page_alloc.c:3325 [inline]
>  free_unref_page+0x19/0x690 mm/page_alloc.c:3404
>  qlink_free mm/kasan/quarantine.c:157 [inline]
>  qlist_free_all+0x6d/0x160 mm/kasan/quarantine.c:176
>  kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:283
>  __kasan_slab_alloc+0xa2/0xc0 mm/kasan/common.c:446
>  kasan_slab_alloc include/linux/kasan.h:260 [inline]
>  slab_post_alloc_hook mm/slab.h:732 [inline]
>  slab_alloc_node mm/slub.c:3230 [inline]
>  kmem_cache_alloc_node+0x255/0x3f0 mm/slub.c:3266
>  __alloc_skb+0x215/0x340 net/core/skbuff.c:414
>  alloc_skb include/linux/skbuff.h:1158 [inline]
>  nlmsg_new include/net/netlink.h:953 [inline]
>  devlink_param_notify+0xba/0x230 net/core/devlink.c:4729
>  devlink_notify_register net/core/devlink.c:9112 [inline]
>  devlink_register+0x398/0x4a0 net/core/devlink.c:9164
>  nsim_drv_probe+0xd81/0x11c0 drivers/net/netdevsim/dev.c:1604
>  call_driver_probe drivers/base/dd.c:517 [inline]
>  really_probe+0x245/0xcc0 drivers/base/dd.c:596
>  __driver_probe_device+0x338/0x4d0 drivers/base/dd.c:752
>  driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:782
>  __device_attach_driver+0x20b/0x2f0 drivers/base/dd.c:899
>  bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:427
>  __device_attach+0x228/0x4a0 drivers/base/dd.c:970
>
> Memory state around the buggy address:
>  ffff88801886e880: fc fc fc fa fc fc fc fc fa fc fc fc fc fb fc fc
>  ffff88801886e900: fc fc fa fc fc fc fc fa fc fc fc fc fa fc fc fc
> >ffff88801886e980: fc fa fc fc fc fc fa fc fc fc fc fa fc fc fc fc
>                                      ^
>  ffff88801886ea00: fa fc fc fc fc fa fc fc fc fc fb fc fc fc fc fa
>  ffff88801886ea80: fc fc fc fc fa fc fc fc fc fb fc fc fc fc fa fc
> ==================================================================
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
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