KASAN: use-after-free Read in devlink_health_reporter_destroy

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 71930d61 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10c8d157100000
kernel config: https://syzkaller.appspot.com/x/.config?x=4c5bc87125719cf4
dashboard link: https://syzkaller.appspot.com/bug?extid=dd0040db0d77d52f98a5
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1421cd3f100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13ccfe4f100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+dd0040...@syzkaller.appspotmail.com

netdevsim netdevsim3 netdevsim0 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
==================================================================
BUG: KASAN: use-after-free in devlink_health_reporter_destroy+0x184/0x1d0 net/core/devlink.c:5476
Read of size 8 at addr ffff88808ca11c20 by task kworker/u4:1/21

CPU: 1 PID: 21 Comm: kworker/u4:1 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x18f/0x20d lib/dump_stack.c:118
print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
__kasan_report mm/kasan/report.c:513 [inline]
kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
devlink_health_reporter_destroy+0x184/0x1d0 net/core/devlink.c:5476
nsim_dev_health_exit+0x8b/0xe0 drivers/net/netdevsim/health.c:317
nsim_dev_reload_destroy+0x132/0x1e0 drivers/net/netdevsim/dev.c:1134
nsim_dev_reload_down+0x6e/0xd0 drivers/net/netdevsim/dev.c:712
devlink_reload+0xc1/0x3a0 net/core/devlink.c:2952
devlink_pernet_pre_exit+0xfb/0x190 net/core/devlink.c:9622
ops_pre_exit_list net/core/net_namespace.c:176 [inline]
cleanup_net+0x451/0xa00 net/core/net_namespace.c:591
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 6819:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
__kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
kmalloc include/linux/slab.h:555 [inline]
kzalloc include/linux/slab.h:669 [inline]
__devlink_health_reporter_create+0x91/0x2f0 net/core/devlink.c:5359
devlink_health_reporter_create+0xa1/0x1d0 net/core/devlink.c:5431
nsim_dev_health_init+0x95/0x3a0 drivers/net/netdevsim/health.c:279
nsim_dev_probe+0xada/0xf80 drivers/net/netdevsim/dev.c:1086
really_probe+0x282/0x8a0 drivers/base/dd.c:525
driver_probe_device+0xfe/0x1d0 drivers/base/dd.c:701
__device_attach_driver+0x1c2/0x220 drivers/base/dd.c:807
bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431
__device_attach+0x28d/0x3f0 drivers/base/dd.c:873
bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491
device_add+0xacf/0x1b00 drivers/base/core.c:2680
nsim_bus_dev_new drivers/net/netdevsim/bus.c:336 [inline]
new_device_store+0x374/0x5c0 drivers/net/netdevsim/bus.c:215
bus_attr_store+0x72/0xa0 drivers/base/bus.c:122
sysfs_kf_write+0x110/0x160 fs/sysfs/file.c:138
kernfs_fop_write+0x268/0x490 fs/kernfs/file.c:315
vfs_write+0x2b0/0x6b0 fs/read_write.c:576
ksys_write+0x12d/0x250 fs/read_write.c:631
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 21:
save_stack+0x1b/0x40 mm/kasan/common.c:48
set_track mm/kasan/common.c:56 [inline]
kasan_set_free_info mm/kasan/common.c:316 [inline]
__kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
__cache_free mm/slab.c:3426 [inline]
kfree+0x103/0x2c0 mm/slab.c:3757
devlink_health_reporter_free net/core/devlink.c:5449 [inline]
devlink_health_reporter_put+0xb7/0xf0 net/core/devlink.c:5456
__devlink_health_reporter_destroy net/core/devlink.c:5463 [inline]
devlink_health_reporter_destroy+0x143/0x1d0 net/core/devlink.c:5475
nsim_dev_health_exit+0x8b/0xe0 drivers/net/netdevsim/health.c:317
nsim_dev_reload_destroy+0x132/0x1e0 drivers/net/netdevsim/dev.c:1134
nsim_dev_reload_down+0x6e/0xd0 drivers/net/netdevsim/dev.c:712
devlink_reload+0xc1/0x3a0 net/core/devlink.c:2952
devlink_pernet_pre_exit+0xfb/0x190 net/core/devlink.c:9622
ops_pre_exit_list net/core/net_namespace.c:176 [inline]
cleanup_net+0x451/0xa00 net/core/net_namespace.c:591
process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
kthread+0x3b5/0x4a0 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff88808ca11c00
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 32 bytes inside of
512-byte region [ffff88808ca11c00, ffff88808ca11e00)
The buggy address belongs to the page:
page:ffffea0002328440 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88808ca11000
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00024ba648 ffffea0002a32788 ffff8880aa000a80
raw: ffff88808ca11000 ffff88808ca11000 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808ca11b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88808ca11b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808ca11c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88808ca11c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808ca11d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Ido Schimmel]

On Mon, Jul 13, 2020 at 03:55:21PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 71930d61 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10c8d157100000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4c5bc87125719cf4
> dashboard link: https://syzkaller.appspot.com/bug?extid=dd0040db0d77d52f98a5
> compiler: gcc (GCC) 10.1.0-syz 20200507
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1421cd3f100000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13ccfe4f100000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+dd0040...@syzkaller.appspotmail.com

#syz fix: devlink: Fix use-after-free when destroying health reporters