Re: [syzbot] [netfilter?] KASAN: slab-use-after-free Read in ip_skb_dst_mtu

[syzbot <syzbot+e5167d7144a62715044c@syzkaller.appspotmail.com>]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in switchdev_deferred_process_work

INFO: task kworker/0:1:9 blocked for more than 143 seconds.
      Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:1     state:D stack:22136 pid:9     tgid:9     ppid:2      flags:0x00004000
Workqueue: events switchdev_deferred_process_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5400 [inline]
 __schedule+0x17d1/0x49f0 kernel/sched/core.c:6727
 __schedule_loop kernel/sched/core.c:6802 [inline]
 schedule+0x149/0x260 kernel/sched/core.c:6817
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6874
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a3/0xd70 kernel/locking/mutex.c:752
 switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
 worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243
 </TASK>
INFO: task kworker/1:2:930 blocked for more than 143 seconds.
      Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:2     state:D stack:21656 pid:930   tgid:930   ppid:2      flags:0x00004000
Workqueue: events linkwatch_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5400 [inline]
 __schedule+0x17d1/0x49f0 kernel/sched/core.c:6727
 __schedule_loop kernel/sched/core.c:6802 [inline]
 schedule+0x149/0x260 kernel/sched/core.c:6817
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6874
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a3/0xd70 kernel/locking/mutex.c:752
 linkwatch_event+0xe/0x60 net/core/link_watch.c:281
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
 worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243
 </TASK>
INFO: task dhcpcd:4736 blocked for more than 143 seconds.
      Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:dhcpcd          state:D stack:20504 pid:4736  tgid:4736  ppid:4735   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5400 [inline]
 __schedule+0x17d1/0x49f0 kernel/sched/core.c:6727
 __schedule_loop kernel/sched/core.c:6802 [inline]
 schedule+0x149/0x260 kernel/sched/core.c:6817
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6874
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a3/0xd70 kernel/locking/mutex.c:752
 rtnl_lock net/core/rtnetlink.c:79 [inline]
 rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
 netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
 netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
 netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
 ___sys_sendmsg net/socket.c:2638 [inline]
 __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f4199ba6a4b
RSP: 002b:00007fff84cbbcc8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f4199ace6c0 RCX: 00007f4199ba6a4b
RDX: 0000000000000000 RSI: 00007fff84ccfe78 RDI: 0000000000000018
RBP: 0000000000000018 R08: 0000000000000000 R09: 00007fff84ccfe78
R10: 0000000000000000 R11: 0000000000000246 R12: ffffffffffffffff
R13: 00007fff84ccfe78 R14: 0000000000000030 R15: 0000000000000001
 </TASK>
INFO: task syz-executor.0:14964 blocked for more than 144 seconds.
      Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.0  state:D stack:20984 pid:14964 tgid:14964 ppid:1      flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5400 [inline]
 __schedule+0x17d1/0x49f0 kernel/sched/core.c:6727
 __schedule_loop kernel/sched/core.c:6802 [inline]
 schedule+0x149/0x260 kernel/sched/core.c:6817
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6874
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x6a3/0xd70 kernel/locking/mutex.c:752
 rtnl_lock net/core/rtnetlink.c:79 [inline]
 rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614
 netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
 netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
 netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
 netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 __sys_sendto+0x3a4/0x4f0 net/socket.c:2191
 __do_sys_sendto net/socket.c:2203 [inline]
 __se_sys_sendto net/socket.c:2199 [inline]
 __x64_sys_sendto+0xde/0x100 net/socket.c:2199
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f49d9c7fa9c
RSP: 002b:00007ffe9fe96940 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f49da8d4620 RCX: 00007f49d9c7fa9c
RDX: 000000000000003c RSI: 00007f49da8d4670 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffe9fe96994 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f49da8d4670 R15: 0000000000000000
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/8:
 #0: ffff888029cdbd38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888029cdbd38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc900000d7d20 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc900000d7d20 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #2: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x19/0x30 net/ipv6/addrconf.c:4686
3 locks held by kworker/0:1/9:
 #0: ffff888014c78938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888014c78938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc900000e7d20 (deferred_process_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc900000e7d20 (deferred_process_work){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #2: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:104
1 lock held by khungtaskd/29:
 #0: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:298 [inline]
 #0: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:750 [inline]
 #0: ffffffff8e130be0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
2 locks held by kworker/u4:2/42:
 #0: ffff8880b953c958 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2a/0x140 kernel/sched/core.c:559
 #1: ffff8880b9528988 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x441/0x770 kernel/sched/psi.c:988
3 locks held by kworker/1:2/930:
 #0: ffff888014c78938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888014c78938 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc900042e7d20 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc900042e7d20 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #2: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xe/0x60 net/core/link_watch.c:281
5 locks held by kworker/u4:7/1097:
 #0: ffff888015ea4938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888015ea4938 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc9000495fd20 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc9000495fd20 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #2: ffffffff8f369810 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0xf5/0xb90 net/core/net_namespace.c:580
 #3: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: default_device_exit_batch+0xe8/0x9d0 net/core/dev.c:11583
 #4: ffffffff8e136578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
 #4: ffffffff8e136578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3a3/0x890 kernel/rcu/tree_exp.h:995
1 lock held by dhcpcd/4736:
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614
3 locks held by kworker/1:3/4809:
 #0: ffff888029cdbd38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888029cdbd38 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc9000356fd20 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc9000356fd20 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #2: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_verify_work+0x19/0x30 net/ipv6/addrconf.c:4686
2 locks held by getty/4822:
 #0: ffff88802a4a50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f062f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b4/0x1e10 drivers/tty/n_tty.c:2201
2 locks held by kworker/1:6/5082:
 #0: ffff888014c7a538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #0: ffff888014c7a538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
 #1: ffffc90004217d20 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2608 [inline]
 #1: ffffc90004217d20 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x825/0x1420 kernel/workqueue.c:2706
1 lock held by syz-executor.0/14964:
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614
1 lock held by syz-executor.0/14988:
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614
1 lock held by syz-executor.0/14995:
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
 #0: ffffffff8f375d88 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x82c/0x1040 net/core/rtnetlink.c:6614

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xfaf/0xff0 kernel/hung_task.c:379
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 270 Comm: kworker/u4:5 Not tainted 6.8.0-rc7-syzkaller-gc381c89de180-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:get_current arch/x86/include/asm/current.h:42 [inline]
RIP: 0010:write_comp_data kernel/kcov.c:235 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x8/0x90 kernel/kcov.c:304
Code: 0a 20 c3 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 4c 8b 04 24 <65> 48 8b 15 b0 4b 70 7e 65 8b 05 b1 4b 70 7e a9 00 01 ff 00 74 10
RSP: 0018:ffffc9000316f758 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 1ffff9200062df35 RCX: ffff88801e230000
RDX: 0000000000000000 RSI: 0000000000004000 RDI: 0000000000000000
RBP: ffffc9000316f9ac R08: ffffffff8b63c78f R09: 0000000000000000
R10: ffffc9000316f960 R11: fffff5200062df37 R12: ffffc9000316f960
R13: 0000000000004000 R14: ffffc9000316f984 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d14f5ec028 CR3: 000000000df32000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 insn_get_modrm+0xbf/0x7a0 arch/x86/lib/insn.c:348
 insn_get_sib arch/x86/lib/insn.c:421 [inline]
 insn_get_displacement+0x13e/0x980 arch/x86/lib/insn.c:464
 insn_get_immediate+0x382/0x13e0 arch/x86/lib/insn.c:632
 insn_get_length arch/x86/lib/insn.c:707 [inline]
 insn_decode+0x370/0x500 arch/x86/lib/insn.c:747
 text_poke_loc_init+0xed/0x870 arch/x86/kernel/alternative.c:2401
 arch_jump_label_transform_queue+0x8f/0x100 arch/x86/kernel/jump_label.c:138
 __jump_label_update+0x177/0x3a0 kernel/jump_label.c:475
 static_key_disable_cpuslocked+0xce/0x1c0 kernel/jump_label.c:235
 static_key_disable+0x1a/0x20 kernel/jump_label.c:243
 toggle_allocation_gate+0x1b8/0x250 mm/kfence/core.c:831
 process_one_work kernel/workqueue.c:2633 [inline]
 process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
 worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
 kthread+0x2ef/0x390 kernel/kthread.c:388
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243
 </TASK>


Tested on:

commit:         c381c89d Merge tag 'spi-fix-v6.8-rc7' of git://git.ker..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git stable
console output: https://syzkaller.appspot.com/x/log.txt?x=13ede469180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c11c5c676adb61f0
dashboard link: https://syzkaller.appspot.com/bug?extid=e5167d7144a62715044c
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=16e50da6180000