linux-kernel - Re: [syzbot] [tipc?] KMSAN: uninit-value in tipc

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Message-ID: <690d95aa.a70a0220.22f260.001f.GAE@google.com>
Date: Thu, 06 Nov 2025 22:46:02 -0800
From: syzbot <syzbot+9a4fbb77c9d4aacd3388@...kaller.appspotmail.com>
To: hariconscious@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [tipc?] KMSAN: uninit-value in tipc_rcv (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in tipc_rcv

=====================================================
BUG: KMSAN: uninit-value in tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_rcv+0x17fa/0x1ea0 net/tipc/node.c:2132
 tipc_l2_rcv_msg+0x213/0x320 net/tipc/bearer.c:668
 __netif_receive_skb_list_ptype net/core/dev.c:6127 [inline]
 __netif_receive_skb_list_core+0x133e/0x16b0 net/core/dev.c:6169
 __netif_receive_skb_list net/core/dev.c:6221 [inline]
 netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6312
 gro_normal_list include/net/gro.h:524 [inline]
 gro_flush_normal include/net/gro.h:532 [inline]
 napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6681
 napi_complete include/linux/netdevice.h:589 [inline]
 tun_get_user+0x5953/0x6d70 drivers/net/tun.c:1924
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
 do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
 x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4977 [inline]
 slab_alloc_node mm/slub.c:5280 [inline]
 kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5332
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:812
 napi_get_frags+0xab/0x250 net/core/gro.c:681
 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
 tun_get_user+0x1352/0x6d70 drivers/net/tun.c:1784
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1999
 do_iter_readv_writev+0x9e1/0xc20 fs/read_write.c:-1
 vfs_writev+0x52a/0x1500 fs/read_write.c:1057
 do_writev+0x1b5/0x580 fs/read_write.c:1103
 __do_sys_writev fs/read_write.c:1171 [inline]
 __se_sys_writev fs/read_write.c:1168 [inline]
 __x64_sys_writev+0x99/0xf0 fs/read_write.c:1168
 x64_sys_call+0x24b1/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 6553 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================


Tested on:

commit:         4a0c9b33 Merge tag 'probes-fixes-v6.18-rc4' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123c7012580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2901a6a99b67fbcc
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
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=104a332f980000