UBSAN: shift-out-of-bounds in gred_change

Status: fixed on 2021/03/10 01:48
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+1819b70451246ed8cf57@syzkaller.appspotmail.com
Fix commit: bd1248f1ddbc net: sched: prevent invalid Scell_log shift count
First crash: 2037d, last: 1978d
Cause bisection: introduced by (bisect log) [release commit]:
commit 4d856f72c10ecb060868ed10ff1b1453943fc6c8
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sun Sep 15 21:19:32 2019 +0000

  Linux 5.3

Crash: UBSAN: undefined-behaviour in gred_change (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
UBSAN: shift-out-of-bounds in gred_change 1 (2) 2021/01/05 23:33

Sample crash report:
IPVS: ftp: loaded support on port[0] = 21
================================================================================
UBSAN: shift-out-of-bounds in ./include/net/red.h:252:22
shift exponent 255 is too large for 32-bit type 'int'
CPU: 0 PID: 8465 Comm: syz-executor194 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:395
 red_set_parms include/net/red.h:252 [inline]
 gred_change_vq net/sched/sch_gred.c:506 [inline]
 gred_change.cold+0xce/0xe2 net/sched/sch_gred.c:702
 qdisc_change net/sched/sch_api.c:1331 [inline]
 tc_modify_qdisc+0xd4e/0x1a30 net/sched/sch_api.c:1633
 rtnetlink_rcv_msg+0x493/0xb40 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x907/0xe10 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xd3/0x130 net/socket.c:672
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2336
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2390
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2423
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x440e69
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 0b 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fff634be6d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004a2730 RCX: 0000000000440e69
RDX: 0000000000000000 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00007fff634be6e0 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000120080522 R11: 0000000000000246 R12: 00000000004a2730
R13: 0000000000402390 R14: 0000000000000000 R15: 0000000000000000
================================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2020/12/27 21:37 net-next-old 3db1a3fa9880 2242f77f .config console log report syz C ci-upstream-net-kasan-gce
2021/02/24 11:04 net-next-old d310ec03a34e fcc6d71b .config console log report info ci-upstream-net-kasan-gce UBSAN: shift-out-of-bounds in gred_change
2021/01/18 03:54 net-next-old 213b97b12580 fd103621 .config console log report info ci-upstream-net-kasan-gce UBSAN: shift-out-of-bounds in gred_change
2021/01/02 20:40 net-next-old 3db1a3fa9880 79264ae3 .config console log report info ci-upstream-net-kasan-gce
2020/12/27 21:05 net-next-old 3db1a3fa9880 2242f77f .config console log report info ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.