[syzbot] [net?] KASAN: null-ptr-deref Write in dst_cache_per_cpu_get (3)

[syzbot <syzbot+c71bf8ad5b74c29baa2f@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    fc96b232f8e7 Merge tag 'pci-v6.15-fixes-2' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1049063f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=170d968a88ba5c06
dashboard link: https://syzkaller.appspot.com/bug?extid=c71bf8ad5b74c29baa2f
compiler:       Debian clang version 15.0.6, Debian LLD 15.0.6

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fd977d7e57de/disk-fc96b232.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ffa0a3b5b655/vmlinux-fc96b232.xz
kernel image: https://storage.googleapis.com/syzbot-assets/44df3bd100d2/bzImage-fc96b232.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c71bf8ad5b74c29baa2f@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: null-ptr-deref in atomic_add_negative_relaxed include/linux/atomic/atomic-instrumented.h:1475 [inline]
BUG: KASAN: null-ptr-deref in rcuref_get include/linux/rcuref.h:67 [inline]
BUG: KASAN: null-ptr-deref in dst_hold include/net/dst.h:238 [inline]
BUG: KASAN: null-ptr-deref in dst_cache_per_cpu_get+0x7d/0x2b0 net/core/dst_cache.c:50
Write of size 4 at addr 0000000000000043 by task kworker/1:0/24

CPU: 1 UID: 0 PID: 24 Comm: kworker/1:0 Not tainted 6.15.0-rc2-syzkaller-00278-gfc96b232f8e7 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: wg-crypt-wg2 wg_packet_tx_worker
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_report+0xe3/0x5b0 mm/kasan/report.c:524
 kasan_report+0x143/0x180 mm/kasan/report.c:634
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x28f/0x2a0 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
 atomic_add_negative_relaxed include/linux/atomic/atomic-instrumented.h:1475 [inline]
 rcuref_get include/linux/rcuref.h:67 [inline]
 dst_hold include/net/dst.h:238 [inline]
 dst_cache_per_cpu_get+0x7d/0x2b0 net/core/dst_cache.c:50
 dst_cache_get_ip6+0x8c/0xf0 net/core/dst_cache.c:133
 send6+0x466/0xbf0 drivers/net/wireguard/socket.c:129
 wg_socket_send_skb_to_peer+0x115/0x1d0 drivers/net/wireguard/socket.c:178
 wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
 wg_packet_tx_worker+0x1bf/0x810 drivers/net/wireguard/send.c:276
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xac3/0x18e0 kernel/workqueue.c:3319
 worker_thread+0x870/0xd50 kernel/workqueue.c:3400
 kthread+0x7b7/0x940 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
==================================================================


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