syzbot


BUG: soft lockup in tc_modify_qdisc (2)

Status: premoderation: reported on 2025/07/27 15:57
Reported-by: syzbot+20433cfd4a1dcc9e70bf@syzkaller.appspotmail.com
First crash: 31d, last: 1d05h
Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 BUG: soft lockup in tc_modify_qdisc 1 C done done 53 639d 671d 0/2 auto-obsoleted due to no activity on 2024/02/06 04:01
android-5-15 BUG: soft lockup in tc_modify_qdisc origin:lts 1 C done done 254 728d 783d 0/2 auto-obsoleted due to no activity on 2023/11/09 01:01
linux-5.15 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 C error 1 817d 817d 0/3 auto-obsoleted due to no activity on 2023/09/11 01:53
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc 1 3 409d 448d 0/3 auto-obsoleted due to no activity on 2024/10/23 00:42
linux-6.1 BUG: soft lockup in tc_modify_qdisc origin:upstream 1 C done 1 816d 816d 3/3 fixed on 2023/07/10 11:22
android-5-10 BUG: soft lockup in tc_modify_qdisc 1 C done done 314 730d 783d 0/2 auto-obsoleted due to no activity on 2023/11/07 07:54
upstream INFO: rcu detected stall in tc_modify_qdisc net 1 C done 595 8d08h 1856d 0/29 upstream: reported C repro on 2020/07/29 05:53
linux-6.1 INFO: rcu detected stall in tc_modify_qdisc (2) origin:upstream 1 C 10 25d 293d 0/3 upstream: reported C repro on 2024/11/08 00:04
linux-5.15 INFO: rcu detected stall in tc_modify_qdisc origin:lts-only 1 C error 11 20d 379d 0/3 upstream: reported C repro on 2024/08/13 15:46
linux-6.6 INFO: rcu detected stall in tc_modify_qdisc 1 1 69d 69d 0/2 upstream: reported on 2025/06/19 23:42

Sample crash report:
RBP: 00007f103ab2ae19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f103accf038 R14: 00007f103accefa0 R15: 00007ffe2e2c2cb8
watchdog: BUG: soft lockup - CPU#1 stuck for 123s! [syz.4.2009:7351]
Modules linked in:
CPU: 1 PID: 7351 Comm: syz.4.2009 Tainted: G        W         5.10.240-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
RIP: 0010:qdisc_tree_reduce_backlog+0xb9/0x340 net/sched/sch_api.c:791
Code: 8b 1b 89 de 83 e6 40 31 ff e8 83 f9 b8 fd 83 e3 40 0f 85 70 02 00 00 49 8d bf a8 00 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 <84> c0 0f 85 db 01 00 00 41 8b 87 a8 00 00 00 89 45 d0 49 83 c7 40
RSP: 0018:ffffc900041fef28 EFLAGS: 00000a02
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: ffff888135592780 RSI: 0000000000000000 RDI: ffff888119a510a8
RBP: ffffc900041fef70 R08: ffff888135592780 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000fffffff1
R13: ffff888119a510cc R14: dffffc0000000000 R15: ffff888119a51000
FS:  00007f10395106c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000001200 CR3: 0000000111f66000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 fq_change+0xb9e/0x10a0 net/sched/sch_fq.c:915
 fq_init+0x3e3/0x5d0 net/sched/sch_fq.c:963
 qdisc_create+0x780/0x1040 net/sched/sch_api.c:1265
 tc_modify_qdisc+0x8da/0x14c0 net/sched/sch_api.c:1725
 rtnetlink_rcv_msg+0x9db/0xb90 net/core/rtnetlink.c:5610
 netlink_rcv_skb+0x1e0/0x430 net/netlink/af_netlink.c:2503
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5628
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x88d/0xb30 net/netlink/af_netlink.c:1914
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 ____sys_sendmsg+0x5a2/0x8c0 net/socket.c:2376
 ___sys_sendmsg+0x1f0/0x260 net/socket.c:2430
 __sys_sendmsg net/socket.c:2459 [inline]
 __do_sys_sendmsg net/socket.c:2468 [inline]
 __se_sys_sendmsg net/socket.c:2466 [inline]
 __x64_sys_sendmsg+0x1e2/0x2a0 net/socket.c:2466
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f103aaa7be9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1039510038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f103accefa0 RCX: 00007f103aaa7be9
RDX: 0000000000000000 RSI: 0000200000001200 RDI: 0000000000000005
RBP: 00007f103ab2ae19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f103accf038 R14: 00007f103accefa0 R15: 00007ffe2e2c2cb8
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline]
NMI backtrace for cpu 0 skipped: idling at default_idle+0x12/0x20 arch/x86/kernel/process.c:717

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/27 05:27 android13-5.10-lts 1154f779f3f3 e12e5ba4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 BUG: soft lockup in tc_modify_qdisc
2025/08/16 21:54 android13-5.10-lts 1154f779f3f3 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 BUG: soft lockup in tc_modify_qdisc
2025/08/15 06:35 android13-5.10-lts 1154f779f3f3 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 BUG: soft lockup in tc_modify_qdisc
2025/07/27 15:56 android13-5.10-lts ad9a98ef27a4 fb8f743d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 BUG: soft lockup in tc_modify_qdisc
* Struck through repros no longer work on HEAD.