KASAN: global-out-of-bounds Read in __hw_addr_add_ex

Hello,

syzbot found the following issue on:

HEAD commit:    7932b172ac7e Revert "riscv: mm: accelerate pagefault when ..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=138db30c980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=71e27a66e3476b52
dashboard link: https://syzkaller.appspot.com/bug?extid=91161fe81857b396c8a0
compiler:       riscv64-linux-gnu-gcc (Debian 12.2.0-13) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: riscv64

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/a741b348759c/non_bootable_disk-7932b172.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/484dae64ac53/vmlinux-7932b172.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0917f9215e08/Image-7932b172.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

==================================================================

BUG: KASAN: global-out-of-bounds in memcmp+0xc0/0xca lib/string.c:676
Read of size 1 at addr ffffffff8905f080 by task syz-executor.1/3813

CPU: 1 PID: 3813 Comm: syz-executor.1 Not tainted 6.10.0-rc1-syzkaller-g7932b172ac7e #0
Hardware name: riscv-virtio,qemu (DT)
Call Trace:
[<ffffffff8000f6f8>] dump_backtrace+0x2e/0x3c arch/riscv/kernel/stacktrace.c:129
[<ffffffff85c29e64>] show_stack+0x34/0x40 arch/riscv/kernel/stacktrace.c:135
[<ffffffff85c83b6c>] __dump_stack lib/dump_stack.c:88 [inline]
[<ffffffff85c83b6c>] dump_stack_lvl+0x122/0x196 lib/dump_stack.c:114
[<ffffffff85c341cc>] print_address_description mm/kasan/report.c:377 [inline]
[<ffffffff85c341cc>] print_report+0x288/0x596 mm/kasan/report.c:488
[<ffffffff8091ed98>] kasan_report+0xec/0x118 mm/kasan/report.c:601
[<ffffffff80920be2>] __asan_report_load1_noabort+0x12/0x1a mm/kasan/report_generic.c:378
[<ffffffff85c00d1e>] memcmp+0xc0/0xca lib/string.c:676
[<ffffffff84a203e2>] __hw_addr_add_ex+0xee/0x676 net/core/dev_addr_lists.c:88
[<ffffffff84a233e2>] __dev_mc_add net/core/dev_addr_lists.c:867 [inline]
[<ffffffff84a233e2>] dev_mc_add+0xac/0x108 net/core/dev_addr_lists.c:885
[<ffffffff84bb54ee>] mrp_init_applicant+0xe8/0x56e net/802/mrp.c:873
[<ffffffff8578898e>] vlan_mvrp_init_applicant+0x26/0x30 net/8021q/vlan_mvrp.c:57
[<ffffffff8577ec66>] register_vlan_dev+0x1b4/0x922 net/8021q/vlan.c:170
[<ffffffff8577f922>] register_vlan_device net/8021q/vlan.c:277 [inline]
[<ffffffff8577f922>] vlan_ioctl_handler+0x54e/0x956 net/8021q/vlan.c:621
[<ffffffff84952e12>] sock_ioctl+0x1f6/0x61a net/socket.c:1305
[<ffffffff80a0f314>] vfs_ioctl fs/ioctl.c:51 [inline]
[<ffffffff80a0f314>] __do_sys_ioctl fs/ioctl.c:907 [inline]
[<ffffffff80a0f314>] __se_sys_ioctl fs/ioctl.c:893 [inline]
[<ffffffff80a0f314>] __riscv_sys_ioctl+0x186/0x1d6 fs/ioctl.c:893
[<ffffffff8000e200>] syscall_handler+0x94/0x118 arch/riscv/include/asm/syscall.h:90
[<ffffffff85c85e24>] do_trap_ecall_u+0x14c/0x214 arch/riscv/kernel/traps.c:330
[<ffffffff85ca872c>] ret_from_exception+0x0/0x64 arch/riscv/kernel/entry.S:112

The buggy address belongs to the variable:
 vlan_mrp_app+0x60/0x3e80

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x8925f
flags: 0xffe000000002000(reserved|node=0|zone=0|lastcpupid=0x7ff)
raw: 0ffe000000002000 ff1c0000002497c8 ff1c0000002497c8 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:
 ffffffff8905ef80: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8905f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff8905f080: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
                   ^
 ffffffff8905f100: 00 00 00 00 00 00 00 00 f9 f9 f9 f9 00 00 00 00
 ffffffff8905f180: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

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