[syzbot] [net?] KASAN: global-out-of-bounds Read in fib6_clean_node (2)

[syzbot <syzbot+ef84446be20ce6c5e514@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    4f79eaa2ceac kbuild: Properly disable -Wunterminated-strin..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=156a4814580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a9a25b7a36123454
dashboard link: https://syzkaller.appspot.com/bug?extid=ef84446be20ce6c5e514
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4108e43f4175/disk-4f79eaa2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/238784ec1e47/vmlinux-4f79eaa2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/670207e0b3e7/bzImage-4f79eaa2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ef84446be20ce6c5e514@syzkaller.appspotmail.com

netlink: 20 bytes leftover after parsing attributes in process `syz.0.4277'.
==================================================================
BUG: KASAN: global-out-of-bounds in fib6_clean_node+0x35d/0x590 net/ipv6/ip6_fib.c:2198
Read of size 8 at addr ffffffff99d13828 by task syz.0.4277/21355

CPU: 0 UID: 0 PID: 21355 Comm: syz.0.4277 Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xb4/0x290 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 fib6_clean_node+0x35d/0x590 net/ipv6/ip6_fib.c:2198
 fib6_walk_continue+0x67b/0x910 net/ipv6/ip6_fib.c:2124
 fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2172
 fib6_clean_tree net/ipv6/ip6_fib.c:2252 [inline]
 __fib6_clean_all+0x234/0x380 net/ipv6/ip6_fib.c:2268
 rt6_sync_up+0x128/0x160 net/ipv6/route.c:4837
 addrconf_notify+0xb1c/0x1010 net/ipv6/addrconf.c:3748
 notifier_call_chain+0x1b6/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
 call_netdevice_notifiers net/core/dev.c:2228 [inline]
 __dev_notify_flags+0x18d/0x2e0 net/core/dev.c:-1
 rtnl_configure_link net/core/rtnetlink.c:-1 [inline]
 rtnl_newlink_create+0x606/0xaf0 net/core/rtnetlink.c:3843
 __rtnl_newlink net/core/rtnetlink.c:3950 [inline]
 rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4065
 rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x21c/0x490 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:727
 ____sys_sendmsg+0x505/0x830 net/socket.c:2566
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
 __sys_sendmsg net/socket.c:2652 [inline]
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbfc4f8e969
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:00007fbfc5de2038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fbfc51b6080 RCX: 00007fbfc4f8e969
RDX: 0000000000000000 RSI: 0000200000000480 RDI: 0000000000000009
RBP: 00007fbfc5010ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbfc51b6080 R15: 00007fffda169088
 </TASK>

The buggy address belongs to the variable:
 binder_devices+0x8/0x20

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x19d13
flags: 0xfff00000002000(reserved|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000002000 ffffea00006744c8 ffffea00006744c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffffffff99d13700: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
 ffffffff99d13780: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>ffffffff99d13800: f9 f9 f9 f9 00 f9 f9 f9 00 00 f9 f9 00 00 00 00
                                  ^
 ffffffff99d13880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff99d13900: 00 00 00 00 00 00 00 00 00 00 04 f9 f9 f9 f9 f9
==================================================================


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