Forwarded: Re: [syzbot] [sctp?] KMSAN: uninit-value in sctp_inq_pop (3)

[syzbot <syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [sctp?] KMSAN: uninit-value in sctp_inq_pop (3)
Author: vnranganath.20@gmail.com

#syz test

On Wed, Oct 22, 2025 at 5:23 PM syzbot <
syzbot+d101e12bccd4095460e7@syzkaller.appspotmail.com> wrote:

> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still
> triggering an issue:
> KMSAN: uninit-value in sctp_inq_pop
>
> =====================================================
> BUG: KMSAN: uninit-value in sctp_inq_pop+0x159c/0x1aa0
> net/sctp/inqueue.c:213
>  sctp_inq_pop+0x159c/0x1aa0 net/sctp/inqueue.c:213
>  sctp_assoc_bh_rcv+0x1a0/0xbc0 net/sctp/associola.c:980
>  sctp_inq_push+0x2a6/0x350 net/sctp/inqueue.c:88
>  sctp_backlog_rcv+0x3c7/0xda0 net/sctp/input.c:331
>  sk_backlog_rcv+0x142/0x420 include/net/sock.h:1158
>  __release_sock+0x1ef/0x380 net/core/sock.c:3180
>  release_sock+0x6b/0x270 net/core/sock.c:3735
>  sctp_sendmsg+0x3a2b/0x49f0 net/sctp/socket.c:2036
>  inet_sendmsg+0x26c/0x2a0 net/ipv4/af_inet.c:853
>  sock_sendmsg_nosec net/socket.c:727 [inline]
>  __sock_sendmsg+0x278/0x3d0 net/socket.c:742
>  sock_sendmsg+0x170/0x280 net/socket.c:765
>  splice_to_socket+0x10e6/0x1a60 fs/splice.c:886
>  do_splice_from fs/splice.c:938 [inline]
>  do_splice+0x1fd2/0x30d0 fs/splice.c:1351
>  __do_splice fs/splice.c:1433 [inline]
>  __do_sys_splice fs/splice.c:1636 [inline]
>  __se_sys_splice+0x549/0x8c0 fs/splice.c:1618
>  __x64_sys_splice+0x114/0x1a0 fs/splice.c:1618
>  x64_sys_call+0x3140/0x3e30
> arch/x86/include/generated/asm/syscalls_64.h:276
>  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 stored to memory at:
>  sctp_inq_pop+0x150b/0x1aa0 net/sctp/inqueue.c:209
>  sctp_assoc_bh_rcv+0x1a0/0xbc0 net/sctp/associola.c:980
>  sctp_inq_push+0x2a6/0x350 net/sctp/inqueue.c:88
>  sctp_backlog_rcv+0x3c7/0xda0 net/sctp/input.c:331
>  sk_backlog_rcv+0x142/0x420 include/net/sock.h:1158
>  __release_sock+0x1ef/0x380 net/core/sock.c:3180
>  release_sock+0x6b/0x270 net/core/sock.c:3735
>  sctp_sendmsg+0x3a2b/0x49f0 net/sctp/socket.c:2036
>  inet_sendmsg+0x26c/0x2a0 net/ipv4/af_inet.c:853
>  sock_sendmsg_nosec net/socket.c:727 [inline]
>  __sock_sendmsg+0x278/0x3d0 net/socket.c:742
>  sock_sendmsg+0x170/0x280 net/socket.c:765
>  splice_to_socket+0x10e6/0x1a60 fs/splice.c:886
>  do_splice_from fs/splice.c:938 [inline]
>  do_splice+0x1fd2/0x30d0 fs/splice.c:1351
>  __do_splice fs/splice.c:1433 [inline]
>  __do_sys_splice fs/splice.c:1636 [inline]
>  __se_sys_splice+0x549/0x8c0 fs/splice.c:1618
>  __x64_sys_splice+0x114/0x1a0 fs/splice.c:1618
>  x64_sys_call+0x3140/0x3e30
> arch/x86/include/generated/asm/syscalls_64.h:276
>  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:4969 [inline]
>  slab_alloc_node mm/slub.c:5272 [inline]
>  kmem_cache_alloc_node_noprof+0x989/0x16b0 mm/slub.c:5324
>  kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:579
>  __alloc_skb+0x347/0x7d0 net/core/skbuff.c:670
>  alloc_skb include/linux/skbuff.h:1383 [inline]
>  sctp_packet_transmit+0x44b/0x46d0 net/sctp/output.c:598
>  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_primitive_SEND+0xd7/0x110 net/sctp/primitive.c:163
>  sctp_sendmsg_to_asoc+0x1db8/0x2250 net/sctp/socket.c:1873
>  sctp_sendmsg+0x3910/0x49f0 net/sctp/socket.c:2031
>  inet_sendmsg+0x26c/0x2a0 net/ipv4/af_inet.c:853
>  sock_sendmsg_nosec net/socket.c:727 [inline]
>  __sock_sendmsg+0x278/0x3d0 net/socket.c:742
>  sock_sendmsg+0x170/0x280 net/socket.c:765
>  splice_to_socket+0x10e6/0x1a60 fs/splice.c:886
>  do_splice_from fs/splice.c:938 [inline]
>  do_splice+0x1fd2/0x30d0 fs/splice.c:1351
>  __do_splice fs/splice.c:1433 [inline]
>  __do_sys_splice fs/splice.c:1636 [inline]
>  __se_sys_splice+0x549/0x8c0 fs/splice.c:1618
>  __x64_sys_splice+0x114/0x1a0 fs/splice.c:1618
>  x64_sys_call+0x3140/0x3e30
> arch/x86/include/generated/asm/syscalls_64.h:276
>  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: 6609 Comm: syz.0.18 Not tainted syzkaller #0
> PREEMPT(none)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 10/02/2025
> =====================================================
>
>
> Tested on:
>
> commit:         552c5071 Merge tag 'vfio-v6.18-rc3' of https://github...
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=145e2d42580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bbd3e7f3c2e28265
> dashboard link:
> https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7
> 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=165fd734580000
>
>