linux-kernel - Re: [syzbot] [nbd?] KASAN: slab-use-after-free Write in recv

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Message-ID: <690818d4.a70a0220.37351b.0015.GAE@google.com>
Date: Sun, 02 Nov 2025 18:52:04 -0800
From: syzbot <syzbot+56fbf4c7ddf65e95c7cc@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, lizhi.xu@...driver.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [nbd?] KASAN: slab-use-after-free Write in recv_work (3)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in get_data

------------[ cut here ]------------
WARNING: kernel/printk/printk_ringbuffer.c:1278 at get_data+0x48a/0x840 kernel/printk/printk_ringbuffer.c:1278, CPU#1: syz.0.527/8152
Modules linked in:
CPU: 1 UID: 0 PID: 8152 Comm: syz.0.527 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:get_data+0x48a/0x840 kernel/printk/printk_ringbuffer.c:1278
Code: 83 c4 f8 48 b8 00 00 00 00 00 fc ff df 41 0f b6 04 07 84 c0 0f 85 ee 01 00 00 44 89 65 00 49 83 c5 08 eb 13 e8 b7 d6 1e 00 90 <0f> 0b 90 eb 05 e8 ac d6 1e 00 45 31 ed 4c 89 e8 48 83 c4 28 5b 41
RSP: 0018:ffffc9000d8f6760 EFLAGS: 00010293
RAX: ffffffff81a1ff09 RBX: 00003fffffffffff RCX: ffff888027288000
RDX: 0000000000000000 RSI: 00003fffffffffff RDI: 0000000000000000
RBP: 0000000000000012 R08: 00000000000010f0 R09: 00000030039f1912
R10: 00000030039f1912 R11: 00001fd8c200001e R12: 0000000000000012
R13: 0000000000000000 R14: ffffc9000d8f68a8 R15: 1ffffffff1c4ab06
FS:  00007f678b3656c0(0000) GS:ffff888125b9c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f678b343f98 CR3: 000000002b512000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 copy_data kernel/printk/printk_ringbuffer.c:1857 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1966 [inline]
 _prb_read_valid+0x672/0xa90 kernel/printk/printk_ringbuffer.c:2143
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2215
 printk_get_next_message+0x15c/0x7b0 kernel/printk/printk.c:2978
 console_emit_next_record kernel/printk/printk.c:3062 [inline]
 console_flush_one_record kernel/printk/printk.c:3194 [inline]
 console_flush_all+0x4cc/0xb10 kernel/printk/printk.c:3268
 __console_flush_and_unlock kernel/printk/printk.c:3298 [inline]
 console_unlock+0xbb/0x190 kernel/printk/printk.c:3338
 vprintk_emit+0x4c5/0x590 kernel/printk/printk.c:2423
 dev_vprintk_emit+0x337/0x3f0 drivers/base/core.c:4914
 dev_printk_emit+0xe0/0x130 drivers/base/core.c:4925
 _dev_info+0x10a/0x160 drivers/base/core.c:4983
 nbd_genl_reconfigure+0x106d/0x1a50 drivers/block/nbd.c:2439
 genl_family_rcv_msg_doit+0x215/0x300 net/netlink/genetlink.c:1115
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0x60e/0x790 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x208/0x470 net/netlink/af_netlink.c:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x82f/0x9e0 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x21c/0x270 net/socket.c:746
 ____sys_sendmsg+0x505/0x830 net/socket.c:2634
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2688
 __sys_sendmsg net/socket.c:2720 [inline]
 __do_sys_sendmsg net/socket.c:2725 [inline]
 __se_sys_sendmsg net/socket.c:2723 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2723
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f678a58efc9
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:00007f678b365038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f678a7e5fa0 RCX: 00007f678a58efc9
RDX: 0000000000000000 RSI: 00002000000002c0 RDI: 0000000000000008
RBP: 00007f678a611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f678a7e6038 R14: 00007f678a7e5fa0 R15: 00007fffd7aaf958
 </TASK>


Tested on:

commit:         98bd8b16 Add linux-next specific files for 20251031
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15ad4532580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=55e89517f3847929
dashboard link: https://syzkaller.appspot.com/bug?extid=56fbf4c7ddf65e95c7cc
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
patch:          https://syzkaller.appspot.com/x/patch.diff?x=153ba012580000