Subject: [syzbot ci] Re: virtio-net: add flow filter for receive timestamps

From: syzbot ci <[email-masked]>
Date: Thu, 29 Jan 2026 05:27:03 -0800

syzbot ci has tested the following series

[v2] virtio-net: add flow filter for receive timestamps
https://lore.kernel.org/all/[email-masked]
* [PATCH RFC v2 1/2] tun: support rx-tstamp
* [PATCH RFC v2 2/2] virtio-net: support receive timestamp

and found the following issue:
WARNING in __copy_overflow

Full report is available here:
https://ci.syzbot.org/series/0b35c8c9-603b-4126-ac04-0095faadb2f5

***

WARNING in __copy_overflow

tree:      net-next
URL:       https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net-next.git
base:      ffeafa65b2b26df2f5b5a6118d3174f17bd12ec5
arch:      amd64
compiler:  Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config:    https://ci.syzbot.org/builds/d8316da2-2688-4d74-bbf4-e8412e24d106/config
C repro:   https://ci.syzbot.org/findings/96af937a-787b-4fd5-baef-529fc80e0bb7/c_repro
syz repro: https://ci.syzbot.org/findings/96af937a-787b-4fd5-baef-529fc80e0bb7/syz_repro

------------[ cut here ]------------
Buffer overflow detected (32 < 1840)!
WARNING: mm/maccess.c:234 at __copy_overflow+0x17/0x30 mm/maccess.c:234, CPU#0: syz.0.17/5993
Modules linked in:
CPU: 0 UID: 0 PID: 5993 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:__copy_overflow+0x1c/0x30 mm/maccess.c:234
Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 53 48 89 f3 89 fd e8 60 b1 c4 ff 48 8d 3d 39 25 d5 0d 89 ee 48 89 da <67> 48 0f b9 3a 5b 5d c3 cc cc cc cc cc cc cc cc cc cc cc cc 90 90
RSP: 0018:ffffc90003b97888 EFLAGS: 00010293
RAX: ffffffff81fdcf50 RBX: 0000000000000730 RCX: ffff88810ccd9d40
RDX: 0000000000000730 RSI: 0000000000000020 RDI: ffffffff8fd2f490
RBP: 0000000000000020 R08: ffffffff8fcec777 R09: 1ffffffff1f9d8ee
R10: dffffc0000000000 R11: ffffffff81742230 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000730 R15: 1ffff92000772f30
FS:  00007f08c446a6c0(0000) GS:ffff88818e32d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f08c4448ff8 CR3: 000000010cec2000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 copy_overflow include/linux/ucopysize.h:41 [inline]
 check_copy_size include/linux/ucopysize.h:50 [inline]
 copy_to_iter include/linux/uio.h:219 [inline]
 tun_put_user drivers/net/tun.c:2089 [inline]
 tun_do_read+0x1f44/0x28a0 drivers/net/tun.c:2190
 tun_chr_read_iter+0x13b/0x260 drivers/net/tun.c:2214
 do_iter_readv_writev+0x619/0x8c0 fs/read_write.c:-1
 vfs_readv+0x288/0x840 fs/read_write.c:1018
 do_readv+0x154/0x2e0 fs/read_write.c:1080
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f08c359acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f08c446a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 00007f08c3815fa0 RCX: 00007f08c359acb9
RDX: 0000000000000002 RSI: 0000200000000080 RDI: 0000000000000003
RBP: 00007f08c3608bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f08c3816038 R14: 00007f08c3815fa0 R15: 00007fff6491da78
 </TASK>
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	90                   	nop
   2:	90                   	nop
   3:	90                   	nop
   4:	90                   	nop
   5:	90                   	nop
   6:	90                   	nop
   7:	90                   	nop
   8:	90                   	nop
   9:	90                   	nop
   a:	90                   	nop
   b:	90                   	nop
   c:	90                   	nop
   d:	90                   	nop
   e:	f3 0f 1e fa          	endbr64
  12:	55                   	push   %rbp
  13:	53                   	push   %rbx
  14:	48 89 f3             	mov    %rsi,%rbx
  17:	89 fd                	mov    %edi,%ebp
  19:	e8 60 b1 c4 ff       	call   0xffc4b17e
  1e:	48 8d 3d 39 25 d5 0d 	lea    0xdd52539(%rip),%rdi        # 0xdd5255e
  25:	89 ee                	mov    %ebp,%esi
  27:	48 89 da             	mov    %rbx,%rdx
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	5b                   	pop    %rbx
  30:	5d                   	pop    %rbp
  31:	c3                   	ret
  32:	cc                   	int3
  33:	cc                   	int3
  34:	cc                   	int3
  35:	cc                   	int3
  36:	cc                   	int3
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	cc                   	int3
  3c:	cc                   	int3
  3d:	cc                   	int3
  3e:	90                   	nop
  3f:	90                   	nop

***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
  Tested-by: [email-masked]

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at [email-masked].