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

[Randy Dunlap]

On 12/31/20 1:09 PM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    3db1a3fa Merge tag 'staging-5.11-rc1' of git://git.kernel...
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=155708db500000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2ae878fbf640b72b
> dashboard link: https://syzkaller.appspot.com/bug?extid=1819b70451246ed8cf57
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=176b78c0d00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12993797500000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1819b70451246ed8cf57@xxxxxxxxxxxxxxxxxxxxxxxxx

#syz fix: net: sched: prevent invalid Scell_log shift count

> 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
> ================================================================================


-- 
~Randy