Re: [syzbot] [net?] WARNING in ipv6_addr_prefix

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: syzbot <syzbot+9596c1b9df18e0ae7261@syzkaller.appspotmail.com>
Date: Thu, 01 May 2025 04:15:34 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    5565acd1e6c4 Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1178cecc580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2e3745cb659ef5d9
> dashboard link: https://syzkaller.appspot.com/bug?extid=9596c1b9df18e0ae7261
> compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=122efd9b980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e99574580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/80798769614c/disk-5565acd1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/435ecb0f1371/vmlinux-5565acd1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/7790d5f923b6/bzImage-5565acd1.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9596c1b9df18e0ae7261@syzkaller.appspotmail.com
> 
> UDPLite6: UDP-Lite is deprecated and scheduled to be removed in 2025, please contact the netdev mailing list
> ------------[ cut here ]------------
> memcpy: detected field-spanning write (size 898) of single field "pfx->in6_u.u6_addr8" at ./include/net/ipv6.h:614 (size 16)
> WARNING: CPU: 0 PID: 5838 at ./include/net/ipv6.h:614 ipv6_addr_prefix+0x124/0x1d0 include/net/ipv6.h:614
> Modules linked in:
> CPU: 0 UID: 0 PID: 5838 Comm: syz-executor414 Not tainted 6.15.0-rc3-syzkaller-00557-g5565acd1e6c4 #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> RIP: 0010:ipv6_addr_prefix+0x124/0x1d0 include/net/ipv6.h:614
> Code: cc e8 70 eb af f7 c6 05 b8 a8 59 05 01 90 b9 10 00 00 00 48 c7 c7 a0 86 7d 8c 4c 89 fe 48 c7 c2 c0 8d 7d 8c e8 4d 4a 74 f7 90 <0f> 0b 90 90 e9 33 ff ff ff e8 3e eb af f7 44 89 e6 48 c7 c7 c0 53
> RSP: 0018:ffffc90003eb7920 EFLAGS: 00010246
> RAX: 8f8f704687b6a900 RBX: ffff8880337f5c50 RCX: ffff88803326da00
> RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
> RBP: 0000000000000000 R08: ffffc90003eb7607 R09: 1ffff920007d6ec0
> R10: dffffc0000000000 R11: fffff520007d6ec1 R12: 0000000000000382
> R13: 1ffff920007d6f4e R14: ffffc90003eb7a84 R15: 0000000000000382
> FS:  0000555594768380(0000) GS:ffff8881260b2000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055d1681c9000 CR3: 0000000078e3e000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  ip6_route_info_create+0x5cc/0xa70 net/ipv6/route.c:3810
>  ip6_route_add+0x29/0x2f0 net/ipv6/route.c:3902
>  ipv6_route_ioctl+0x35c/0x480 net/ipv6/route.c:4539
>  inet6_ioctl+0x219/0x280 net/ipv6/af_inet6.c:577

This will fix it.
https://lore.kernel.org/netdev/20250501005335.53683-1-kuniyu@amazon.com/

so speculatively:

#syz fix: ipv6: Restore fib6_config validation for SIOCADDRT.