[syzbot] [net?] KASAN: null-ptr-deref Write in rcuref_put (4)

[syzbot <syzbot+27d7cfbc93457e472e00@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    a52a3c18cdf3 Merge tag 'ntb-6.15' of https://github.com/jo..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15764be4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=695196aa2bd08d99
dashboard link: https://syzkaller.appspot.com/bug?extid=27d7cfbc93457e472e00
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/326c7eeab15a/disk-a52a3c18.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/10c3ccb3546c/vmlinux-a52a3c18.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0bd8832c1d9c/bzImage-a52a3c18.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+27d7cfbc93457e472e00@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_sub_return_release include/linux/atomic/atomic-instrumented.h:326 [inline]
BUG: KASAN: null-ptr-deref in __rcuref_put include/linux/rcuref.h:89 [inline]
BUG: KASAN: null-ptr-deref in rcuref_put+0x1a1/0x240 include/linux/rcuref.h:153
Write of size 4 at addr 0000000000000041 by task udevd/6807

CPU: 1 UID: 0 PID: 6807 Comm: udevd Not tainted 6.14.0-syzkaller-13389-ga52a3c18cdf3 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <IRQ>
 __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_sub_return_release include/linux/atomic/atomic-instrumented.h:326 [inline]
 __rcuref_put include/linux/rcuref.h:89 [inline]
 rcuref_put+0x1a1/0x240 include/linux/rcuref.h:153
 dst_release+0x24/0x1b0 net/core/dst.c:167
 dst_cache_reset_now+0x1b0/0x220 net/core/dst_cache.c:183
 wg_socket_clear_peer_endpoint_src+0x40/0x50 drivers/net/wireguard/socket.c:312
 wg_expired_retransmit_handshake+0xd3/0x2d0 drivers/net/wireguard/timers.c:73
 call_timer_fn+0x189/0x650 kernel/time/timer.c:1789
 expire_timers kernel/time/timer.c:1840 [inline]
 __run_timers kernel/time/timer.c:2414 [inline]
 __run_timer_base+0x66e/0x8e0 kernel/time/timer.c:2426
 run_timer_base kernel/time/timer.c:2435 [inline]
 run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2445
 handle_softirqs+0x2d6/0x9b0 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xfb/0x220 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xd9/0x140 kernel/locking/spinlock.c:194
Code: 9c 8f 44 24 20 42 80 3c 2b 00 74 08 4c 89 f7 e8 3d bd ff f5 f6 44 24 21 02 75 55 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 32 58 65 f5 65 8b 05 0b 1e 3a 07 85 c0 74 46 48 c7 04 24 0e 36
RSP: 0018:ffffc90003f97280 EFLAGS: 00000206
RAX: ba8754475f048600 RBX: 1ffff920007f2e54 RCX: ffffffff81cb37bc
RDX: 0000000000000000 RSI: ffffffff8e687288 RDI: 0000000000000001
RBP: ffffc90003f97310 R08: ffffffff905eac77 R09: 1ffffffff20bd58e
R10: dffffc0000000000 R11: fffffbfff20bd58f R12: 1ffff920007f2e50
R13: dffffc0000000000 R14: ffffc90003f972a0 R15: 0000000000000246
 __debug_check_no_obj_freed lib/debugobjects.c:1108 [inline]
 debug_check_no_obj_freed+0x572/0x590 lib/debugobjects.c:1129
 free_pages_prepare mm/page_alloc.c:1269 [inline]
 free_unref_folios+0x576/0x17e0 mm/page_alloc.c:2737
 folios_put_refs+0x70a/0x800 mm/swap.c:992
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x595/0x1820 mm/shmem.c:1125
 shmem_truncate_range mm/shmem.c:1237 [inline]
 shmem_evict_inode+0x29d/0xa80 mm/shmem.c:1365
 evict+0x4f9/0x9b0 fs/inode.c:810
 __dentry_kill+0x20d/0x630 fs/dcache.c:660
 dput+0x19f/0x2b0 fs/dcache.c:902
 __fput+0x60b/0x9f0 fs/file_table.c:473
 task_work_run+0x251/0x310 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x13f/0x340 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8f833170a8
Code: 48 8b 05 83 9d 0d 00 64 c7 00 16 00 00 00 83 c8 ff 48 83 c4 20 5b c3 64 8b 04 25 18 00 00 00 85 c0 75 20 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 76 5b 48 8b 15 51 9d 0d 00 f7 d8 64 89 02 48 83
RSP: 002b:00007ffc3678eaf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 00007f8f83761ae0 RCX: 00007f8f833170a8
RDX: 00005574fff315c8 RSI: 00007ffc3678e2f8 RDI: 0000000000000008
RBP: 00005571a8e7a620 R08: 0000000000000006 R09: cd47be37b8f960f8
R10: 000000000000010f R11: 0000000000000246 R12: 0000000000000002
R13: 00005571a8e8a890 R14: 0000000000000008 R15: 00005571a8e73910
 </TASK>
==================================================================
----------------
Code disassembly (best guess):
   0:	9c                   	pushf
   1:	8f 44 24 20          	pop    0x20(%rsp)
   5:	42 80 3c 2b 00       	cmpb   $0x0,(%rbx,%r13,1)
   a:	74 08                	je     0x14
   c:	4c 89 f7             	mov    %r14,%rdi
   f:	e8 3d bd ff f5       	call   0xf5ffbd51
  14:	f6 44 24 21 02       	testb  $0x2,0x21(%rsp)
  19:	75 55                	jne    0x70
  1b:	41 f7 c7 00 02 00 00 	test   $0x200,%r15d
  22:	74 01                	je     0x25
  24:	fb                   	sti
  25:	bf 01 00 00 00       	mov    $0x1,%edi
* 2a:	e8 32 58 65 f5       	call   0xf5655861 <-- trapping instruction
  2f:	65 8b 05 0b 1e 3a 07 	mov    %gs:0x73a1e0b(%rip),%eax        # 0x73a1e41
  36:	85 c0                	test   %eax,%eax
  38:	74 46                	je     0x80
  3a:	48                   	rex.W
  3b:	c7                   	.byte 0xc7
  3c:	04 24                	add    $0x24,%al
  3e:	0e                   	(bad)
  3f:	36                   	ss


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