netdev - Re: [syzbot] [sctp?] KMSAN: uninit-value in sctp_assoc_bh

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Message-ID: <68869950.a00a0220.b12ec.006c.GAE@google.com>
Date: Sun, 27 Jul 2025 14:25:36 -0700
From: syzbot <syzbot+773e51afe420baaf0e2b@...kaller.appspotmail.com>
To: davem@...emloft.net, edumazet@...gle.com, horms@...nel.org, 
	kuba@...nel.org, linux-kernel@...r.kernel.org, linux-sctp@...r.kernel.org, 
	lucien.xin@...il.com, marcelo.leitner@...il.com, netdev@...r.kernel.org, 
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [sctp?] KMSAN: uninit-value in sctp_assoc_bh_rcv

syzbot has found a reproducer for the following issue on:

HEAD commit:    ec2df4364666 Merge tag 'spi-fix-v6.16-rc7' of git://git.ke..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=126d74f0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7753c32e11ff6a95
dashboard link: https://syzkaller.appspot.com/bug?extid=773e51afe420baaf0e2b
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=14e838a2580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1084a782580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3f86f1075111/disk-ec2df436.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c90594c19d7f/vmlinux-ec2df436.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8eac8db13156/bzImage-ec2df436.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+773e51afe420baaf0e2b@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in sctp_assoc_bh_rcv+0x34e/0xbc0 net/sctp/associola.c:987
 sctp_assoc_bh_rcv+0x34e/0xbc0 net/sctp/associola.c:987
 sctp_inq_push+0x2a3/0x350 net/sctp/inqueue.c:88
 sctp_backlog_rcv+0x3c7/0xda0 net/sctp/input.c:331
 sk_backlog_rcv+0x142/0x420 include/net/sock.h:1148
 __release_sock+0x1d3/0x330 net/core/sock.c:3213
 release_sock+0x6b/0x270 net/core/sock.c:3767
 sctp_wait_for_connect+0x458/0x820 net/sctp/socket.c:9367
 sctp_sendmsg_to_asoc+0x223a/0x2260 net/sctp/socket.c:1886
 sctp_sendmsg+0x3910/0x49f0 net/sctp/socket.c:2032
 inet_sendmsg+0x269/0x2a0 net/ipv4/af_inet.c:851
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x278/0x3d0 net/socket.c:727
 __sys_sendto+0x593/0x720 net/socket.c:2180
 __do_sys_sendto net/socket.c:2187 [inline]
 __se_sys_sendto net/socket.c:2183 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2183
 x64_sys_call+0x3c0b/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:45
 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:4154 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_node_track_caller_noprof+0x96d/0x12f0 mm/slub.c:4347
 kmalloc_reserve+0x22f/0x4b0 net/core/skbuff.c:601
 __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
 alloc_skb include/linux/skbuff.h:1336 [inline]
 sctp_packet_pack net/sctp/output.c:472 [inline]
 sctp_packet_transmit+0x18a1/0x46d0 net/sctp/output.c:621
 sctp_outq_flush_transports net/sctp/outqueue.c:1173 [inline]
 sctp_outq_flush+0x1c7d/0x67c0 net/sctp/outqueue.c:1221
 sctp_outq_uncork+0x9e/0xc0 net/sctp/outqueue.c:764
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1204 [inline]
 sctp_do_sm+0x8c8e/0x9720 net/sctp/sm_sideeffect.c:1175
 sctp_assoc_bh_rcv+0x88b/0xbc0 net/sctp/associola.c:1034
 sctp_inq_push+0x2a3/0x350 net/sctp/inqueue.c:88
 sctp_backlog_rcv+0x3c7/0xda0 net/sctp/input.c:331
 sk_backlog_rcv+0x142/0x420 include/net/sock.h:1148
 __release_sock+0x1d3/0x330 net/core/sock.c:3213
 release_sock+0x6b/0x270 net/core/sock.c:3767
 sctp_wait_for_connect+0x458/0x820 net/sctp/socket.c:9367
 sctp_sendmsg_to_asoc+0x223a/0x2260 net/sctp/socket.c:1886
 sctp_sendmsg+0x3910/0x49f0 net/sctp/socket.c:2032
 inet_sendmsg+0x269/0x2a0 net/ipv4/af_inet.c:851
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x278/0x3d0 net/socket.c:727
 __sys_sendto+0x593/0x720 net/socket.c:2180
 __do_sys_sendto net/socket.c:2187 [inline]
 __se_sys_sendto net/socket.c:2183 [inline]
 __x64_sys_sendto+0x130/0x200 net/socket.c:2183
 x64_sys_call+0x3c0b/0x3db0 arch/x86/include/generated/asm/syscalls_64.h:45
 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: 0 UID: 0 PID: 5812 Comm: syz-executor343 Not tainted 6.16.0-rc7-syzkaller-00140-gec2df4364666 #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
=====================================================


---
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#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.