KASAN: global-out-of-bounds Write in record_print_text

KASAN: global-out-of-bounds Write in record_print_text

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    bc085f8f Add linux-next specific files for 20210121
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17a726a4d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1224bbf217b0bec8
dashboard link: https://syzkaller.appspot.com/bug?extid=db1faa35484efb6a54ea
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1173b294d00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1035c13b500000

The issue was bisected to:

commit f0e386ee0c0b71ea6f7238506a4d0965a2dbef11
Author: John Ogness <john.ogness@linutronix.de>
Date:   Thu Jan 14 17:04:12 2021 +0000

    printk: fix buffer overflow potential for print_text()

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=11671b84d00000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=13671b84d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=15671b84d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+db1faa35484efb6a54ea@syzkaller.appspotmail.com
Fixes: f0e386ee0c0b ("printk: fix buffer overflow potential for print_text()")

netdevsim netdevsim0 netdevsim3 (unregistering): unset [1, 0] type 2 family 0 port 6081 - 0
==================================================================
BUG: KASAN: global-out-of-bounds in record_print_text+0x33f/0x380 kernel/printk/printk.c:1401
Write of size 1 at addr ffffffff8f09f144 by task kworker/u4:0/9

CPU: 1 PID: 9 Comm: kworker/u4:0 Not tainted 5.11.0-rc4-next-20210121-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:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5/0x2f8 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:397 [inline]
 kasan_report.cold+0x79/0xd5 mm/kasan/report.c:414
 record_print_text+0x33f/0x380 kernel/printk/printk.c:1401
 console_unlock+0x318/0xbb0 kernel/printk/printk.c:2555
 vprintk_emit+0x189/0x490 kernel/printk/printk.c:2092
 dev_vprintk_emit+0x36e/0x3b2 drivers/base/core.c:4358
 dev_printk_emit+0xba/0xf1 drivers/base/core.c:4369
 __netdev_printk+0x1c6/0x27a net/core/dev.c:11073
 netdev_info+0xd7/0x109 net/core/dev.c:11128
 nsim_udp_tunnel_unset_port.cold+0x95/0xb8 drivers/net/netdevsim/udp_tunnels.c:64
 udp_tunnel_nic_device_sync_one net/ipv4/udp_tunnel_nic.c:225 [inline]
 udp_tunnel_nic_device_sync_by_port net/ipv4/udp_tunnel_nic.c:246 [inline]
 __udp_tunnel_nic_device_sync.part.0+0xa4c/0xcb0 net/ipv4/udp_tunnel_nic.c:289
 __udp_tunnel_nic_device_sync net/ipv4/udp_tunnel_nic.c:283 [inline]
 udp_tunnel_nic_flush+0x2b4/0x5e0 net/ipv4/udp_tunnel_nic.c:668
 udp_tunnel_nic_unregister net/ipv4/udp_tunnel_nic.c:869 [inline]
 udp_tunnel_nic_netdevice_event+0x65c/0x19a0 net/ipv4/udp_tunnel_nic.c:909
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:83
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:2040
 call_netdevice_notifiers_extack net/core/dev.c:2052 [inline]
 call_netdevice_notifiers net/core/dev.c:2066 [inline]
 rollback_registered_many+0x92e/0x14c0 net/core/dev.c:9513
 rollback_registered net/core/dev.c:9558 [inline]
 unregister_netdevice_queue+0x2dd/0x570 net/core/dev.c:10734
 unregister_netdevice include/linux/netdevice.h:2853 [inline]
 nsim_destroy+0x35/0x70 drivers/net/netdevsim/netdev.c:338
 __nsim_dev_port_del+0x144/0x1e0 drivers/net/netdevsim/dev.c:967
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:980 [inline]
 nsim_dev_reload_destroy+0xff/0x1e0 drivers/net/netdevsim/dev.c:1158
 nsim_dev_reload_down+0x6e/0xd0 drivers/net/netdevsim/dev.c:725
 devlink_reload+0x15a/0x5e0 net/core/devlink.c:3191
 devlink_pernet_pre_exit+0x154/0x220 net/core/devlink.c:10329
 ops_pre_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x451/0xb10 net/core/net_namespace.c:592
 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

The buggy address belongs to the variable:
 dmesg_restrict+0x24/0x40

Memory state around the buggy address:
 ffffffff8f09f000: f9 f9 f9 f9 01 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
 ffffffff8f09f080: f9 f9 f9 f9 01 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
>ffffffff8f09f100: f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
                                           ^
 ffffffff8f09f180: 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00
 ffffffff8f09f200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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