KASAN: use-after-free Read in vlan_dev_get_iflink

From: syzbot
Date: Thu Jul 23 2020 - 14:12:26 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 8c26c87b Merge tag 'sound-5.8-rc7' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=128af5ef100000
kernel config: https://syzkaller.appspot.com/x/.config?x=f87a5e4232fdb267
dashboard link: https://syzkaller.appspot.com/bug?extid=d702fd2351989927037c
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1567cae8900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=150631b4900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d702fd2351989927037c@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in vlan_dev_get_iflink+0x5f/0x70 net/8021q/vlan_dev.c:767
Read of size 4 at addr ffff888094a76100 by task syz-executor015/9454

CPU: 1 PID: 9454 Comm: syz-executor015 Not tainted 5.8.0-rc6-syzkaller #0
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+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
vlan_dev_get_iflink+0x5f/0x70 net/8021q/vlan_dev.c:767
dev_get_iflink+0x73/0xe0 net/core/dev.c:814
rfc2863_policy+0x243/0x2e0 net/core/link_watch.c:41
linkwatch_do_dev+0x2a/0x180 net/core/link_watch.c:160
linkwatch_forget_dev+0x16a/0x200 net/core/link_watch.c:237
netdev_wait_allrefs net/core/dev.c:9678 [inline]
netdev_run_todo+0x258/0xac0 net/core/dev.c:9774
rtnl_unlock net/core/rtnetlink.c:112 [inline]
rtnetlink_rcv_msg+0x45b/0xad0 net/core/rtnetlink.c:5461
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x446cf9
Code: Bad RIP value.
RSP: 002b:00007f4a27e29d98 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dbc78 RCX: 0000000000446cf9
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000006
RBP: 00000000006dbc70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dbc7c
R13: 0000000040000000 R14: 0000001000000000 R15: 0705001000000048

Allocated by task 9440:
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
kmalloc_node include/linux/slab.h:578 [inline]
kvmalloc_node+0x61/0xf0 mm/util.c:574
kvmalloc include/linux/mm.h:753 [inline]
kvzalloc include/linux/mm.h:761 [inline]
alloc_netdev_mqs+0x97/0xdc0 net/core/dev.c:9938
rtnl_create_link+0x219/0xad0 net/core/rtnetlink.c:3067
__rtnl_newlink+0xfa0/0x1730 net/core/rtnetlink.c:3329
rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3397
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5460
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 9461:
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
kvfree+0x42/0x50 mm/util.c:603
device_release+0x71/0x200 drivers/base/core.c:1579
kobject_cleanup lib/kobject.c:693 [inline]
kobject_release lib/kobject.c:722 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1c0/0x270 lib/kobject.c:739
netdev_run_todo+0x765/0xac0 net/core/dev.c:9797
rtnl_unlock net/core/rtnetlink.c:112 [inline]
rtnetlink_rcv_msg+0x45b/0xad0 net/core/rtnetlink.c:5461
netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
___sys_sendmsg+0xf3/0x170 net/socket.c:2406
__sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888094a76000
which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 256 bytes inside of
4096-byte region [ffff888094a76000, ffff888094a77000)
The buggy address belongs to the page:
page:ffffea0002529d80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea0002529d80 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea000251fe88 ffffea0002375c88 ffff8880aa002000
raw: 0000000000000000 ffff888094a76000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888094a76000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888094a76080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888094a76100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888094a76180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888094a76200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

---
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Next message: Marek BehÃn: "[PATCH RFC leds + net-next v2 1/1] net: phy: marvell: add support for PHY LEDs via LED class"
Previous message: Song Liu: "[PATCH v5 bpf-next 1/5] bpf: separate bpf_get_[stack|stackid] for perf events BPF"
Next in thread: Cong Wang: "Re: KASAN: use-after-free Read in vlan_dev_get_iflink"
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