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

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Message-ID: <688f2e51.050a0220.1fc43d.0002.GAE@google.com>
Date: Sun, 03 Aug 2025 02:39:29 -0700
From: syzbot <syzbot+9a4fbb77c9d4aacd3388@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, 
	jmaloy@...hat.com, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com, 
	tipc-discussion@...ts.sourceforge.net
Subject: Re: [syzbot] [tipc?] KMSAN: uninit-value in tipc_rcv (2)

syzbot has found a reproducer for the following issue on:

HEAD commit:    89748acdf226 Merge tag 'drm-next-2025-08-01' of https://gi..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1395bcf0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7ff65239b4835001
dashboard link: https://syzkaller.appspot.com/bug?extid=9a4fbb77c9d4aacd3388
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1625ff82580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=131bb834580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ce090dd92dc2/disk-89748acd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/32b5903a7759/vmlinux-89748acd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dc68a867773d/bzImage-89748acd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9a4fbb77c9d4aacd3388@...kaller.appspotmail.com

tipc: Started in network mode
tipc: Node identity 4689370d27fe, cluster identity 4711
tipc: Enabled bearer <eth:syzkaller0>, priority 0
=====================================================
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:6027 [inline]
 __netif_receive_skb_list_core+0x133b/0x16b0 net/core/dev.c:6069
 __netif_receive_skb_list net/core/dev.c:6121 [inline]
 netif_receive_skb_list_internal+0xee7/0x1530 net/core/dev.c:6212
 gro_normal_list include/net/gro.h:532 [inline]
 gro_flush_normal include/net/gro.h:540 [inline]
 napi_complete_done+0x3fb/0x7d0 net/core/dev.c:6581
 napi_complete include/linux/netdevice.h:589 [inline]
 tun_get_user+0x4c0d/0x6ca0 drivers/net/tun.c:1921
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 do_iter_readv_writev+0x947/0xba0 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+0x24b1/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 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:4186 [inline]
 slab_alloc_node mm/slub.c:4229 [inline]
 kmem_cache_alloc_node_noprof+0x818/0xf00 mm/slub.c:4281
 kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:578
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:669
 napi_alloc_skb+0xc1/0x740 net/core/skbuff.c:811
 napi_get_frags+0xab/0x250 net/core/gro.c:673
 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
 tun_get_user+0x134f/0x6ca0 drivers/net/tun.c:1784
 tun_chr_write_iter+0x3e9/0x5c0 drivers/net/tun.c:1996
 do_iter_readv_writev+0x947/0xba0 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+0x24b1/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5808 Comm: syz-executor123 Not tainted 6.16.0-syzkaller-10499-g89748acdf226 #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
=====================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.