Re: UBSAN: shift-out-of-bounds in choke_change

[Randy Dunlap]

Hi bot,

On 12/29/20 10:58 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    71c5f031 Merge tag 'docs-5.11-2' of git://git.lwn.net/linux
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15103693500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3e7e34a83d606100
> dashboard link: https://syzkaller.appspot.com/bug?extid=4eda8c01ca2315d1722e
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=143d33ff500000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13725277500000
> 
> Bisection is inconclusive: the issue happens on the oldest tested release.
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=137f60db500000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=10ff60db500000
> console output: https://syzkaller.appspot.com/x/log.txt?x=177f60db500000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+4eda8c01ca2315d1722e@xxxxxxxxxxxxxxxxxxxxxxxxx

#syz dup: UBSAN: shift-out-of-bounds in sfq_init

Fixed by:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=bd1248f1ddbc48b0c30565fce897a3b6423313b8


> netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
> ================================================================================
> UBSAN: shift-out-of-bounds in ./include/net/red.h:252:22
> shift exponent 96 is too large for 32-bit type 'int'
> CPU: 0 PID: 8513 Comm: syz-executor800 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]
>  choke_change.cold+0xce/0x115 net/sched/sch_choke.c:413
>  qdisc_create+0x4ba/0x13a0 net/sched/sch_api.c:1246
>  tc_modify_qdisc+0x4c8/0x1a30 net/sched/sch_api.c:1662
>  rtnetlink_rcv_msg+0x498/0xb80 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+0x907/0xe40 net/netlink/af_netlink.c:1919
>  sock_sendmsg_nosec net/socket.c:652 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:672
>  ____sys_sendmsg+0x6e8/0x810 net/socket.c:2345
>  ___sys_sendmsg+0xf3/0x170 net/socket.c:2399
>  __sys_sendmsg+0xe5/0x1b0 net/socket.c:2432
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x4437b9
> 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 eb 0d fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007fff205ca1d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004437b9
> RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000004
> RBP: 00007fff205ca1e0 R08: 0000000001bbbbbb R09: 0000000001bbbbbb
> R10: 0000000001bbbbbb R11: 0000000000000246 R12: 00007fff205ca1f0
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> ================================================================================
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches
> 


-- 
~Randy