syzbot


general protection fault in qdisc_tree_reduce_backlog

Status: upstream: reported on 2025/07/16 18:27
Reported-by: syzbot+6f98c635b71269f74ec1@syzkaller.appspotmail.com
First crash: 7d17h, last: 7d17h
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 general protection fault in qdisc_tree_reduce_backlog origin:lts 2 C 10 3d15h 8d01h 0/2 upstream: reported C repro on 2025/07/16 10:37
upstream general protection fault in qdisc_tree_reduce_backlog net 8 C done 255 7d10h 20d 27/29 upstream: reported C repro on 2025/07/04 05:20
linux-6.1 BUG: unable to handle kernel paging request in qdisc_tree_reduce_backlog origin:lts-only 8 C error 8 7d18h 13d 0/3 upstream: reported C repro on 2025/07/10 22:10
linux-5.15 BUG: unable to handle kernel paging request in qdisc_tree_reduce_backlog origin:lts-only 8 C 10 7d22h 11d 0/3 upstream: reported C repro on 2025/07/13 10:38

Sample crash report:
general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027]
CPU: 0 PID: 12677 Comm: syz.3.2229 Not tainted 6.6.98-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:qdisc_tree_reduce_backlog+0x220/0x470 net/sched/sch_api.c:805
Code: 74 08 48 89 ef e8 90 45 56 f9 4d 89 ef 85 db 74 0a e8 a4 96 fd f8 4c 89 f5 eb 7a 48 8b 6d 00 48 8d 45 20 48 89 c3 48 c1 eb 03 <42> 80 3c 33 00 48 89 04 24 74 0d 48 8b 3c 24 e8 5c 45 56 f9 48 8b
RSP: 0018:ffffc9000362edc8 EFLAGS: 00010202
RAX: 0000000000000020 RBX: 0000000000000004 RCX: 0000000000000002
RDX: ffff888022ffbc00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff888022ffbc00 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000000affe0
R13: ffff88807ecea800 R14: dffffc0000000000 R15: ffff88807ecea800
FS:  00007ff96f5d06c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3b0d30 CR3: 000000006c4d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 codel_change+0x974/0xdb0 net/sched/sch_codel.c:177
 codel_init+0x1fd/0x3e0 net/sched/sch_codel.c:196
 qdisc_create+0x8eb/0x1050 net/sched/sch_api.c:1322
 tc_modify_qdisc+0xb13/0x1be0 net/sched/sch_api.c:-1
 rtnetlink_rcv_msg+0x7c7/0xf10 net/core/rtnetlink.c:6475
 netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
 netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
 netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
 netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg net/socket.c:745 [inline]
 ____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
 ___sys_sendmsg+0x220/0x290 net/socket.c:2649
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2687 [inline]
 __se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7ff96e78e929
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:00007ff96f5d0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007ff96e9b5fa0 RCX: 00007ff96e78e929
RDX: 0000000000004000 RSI: 0000200000000280 RDI: 0000000000000003
RBP: 00007ff96e810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff96e9b5fa0 R15: 00007ffffdedc278
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:qdisc_tree_reduce_backlog+0x220/0x470 net/sched/sch_api.c:805
Code: 74 08 48 89 ef e8 90 45 56 f9 4d 89 ef 85 db 74 0a e8 a4 96 fd f8 4c 89 f5 eb 7a 48 8b 6d 00 48 8d 45 20 48 89 c3 48 c1 eb 03 <42> 80 3c 33 00 48 89 04 24 74 0d 48 8b 3c 24 e8 5c 45 56 f9 48 8b
RSP: 0018:ffffc9000362edc8 EFLAGS: 00010202
RAX: 0000000000000020 RBX: 0000000000000004 RCX: 0000000000000002
RDX: ffff888022ffbc00 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff888022ffbc00 R09: 0000000000000002
R10: 00000000ffffffff R11: 0000000000000002 R12: 00000000000affe0
R13: ffff88807ecea800 R14: dffffc0000000000 R15: ffff88807ecea800
FS:  00007ff96f5d06c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3b0d30 CR3: 000000006c4d2000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000001000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	74 08                	je     0xa
   2:	48 89 ef             	mov    %rbp,%rdi
   5:	e8 90 45 56 f9       	call   0xf956459a
   a:	4d 89 ef             	mov    %r13,%r15
   d:	85 db                	test   %ebx,%ebx
   f:	74 0a                	je     0x1b
  11:	e8 a4 96 fd f8       	call   0xf8fd96ba
  16:	4c 89 f5             	mov    %r14,%rbp
  19:	eb 7a                	jmp    0x95
  1b:	48 8b 6d 00          	mov    0x0(%rbp),%rbp
  1f:	48 8d 45 20          	lea    0x20(%rbp),%rax
  23:	48 89 c3             	mov    %rax,%rbx
  26:	48 c1 eb 03          	shr    $0x3,%rbx
* 2a:	42 80 3c 33 00       	cmpb   $0x0,(%rbx,%r14,1) <-- trapping instruction
  2f:	48 89 04 24          	mov    %rax,(%rsp)
  33:	74 0d                	je     0x42
  35:	48 8b 3c 24          	mov    (%rsp),%rdi
  39:	e8 5c 45 56 f9       	call   0xf956459a
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/07/16 18:26 linux-6.6.y 9247f4e6573a 124ec9cc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan general protection fault in qdisc_tree_reduce_backlog
* Struck through repros no longer work on HEAD.