[syzbot] [net?] KMSAN: uninit-value in cmsghdr_from_user_compat_to_kern

Hello,

syzbot found the following issue on:

HEAD commit:    7367539ad4b0 Merge tag 'cxl-fixes-6.9-rc7' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1444078b180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bbf567496022057b
dashboard link: https://syzkaller.appspot.com/bug?extid=bbafcc77279b6c156e52
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b037b3fdb412/disk-7367539a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/715a45b086cb/vmlinux-7367539a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a13ab40a70b3/bzImage-7367539a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bbafcc77279b6c156e52@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in cmsghdr_from_user_compat_to_kern+0x568/0x10d0 net/compat.c:154
 cmsghdr_from_user_compat_to_kern+0x568/0x10d0 net/compat.c:154
 ____sys_sendmsg+0x222/0xb60 net/socket.c:2546
 __sys_sendmsg_sock+0x42/0x60 net/socket.c:2650
 io_sendmsg+0x47a/0x1020 io_uring/net.c:453
 io_issue_sqe+0x371/0x1150 io_uring/io_uring.c:1897
 io_wq_submit_work+0xa17/0xeb0 io_uring/io_uring.c:2006
 io_worker_handle_work+0xc3a/0x2050 io_uring/io-wq.c:596
 io_wq_worker+0x5a1/0x1370 io_uring/io-wq.c:649
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
 io_sendmsg+0x6a4/0x1020 io_uring/net.c:435
 io_issue_sqe+0x371/0x1150 io_uring/io_uring.c:1897
 io_wq_submit_work+0xa17/0xeb0 io_uring/io_uring.c:2006
 io_worker_handle_work+0xc3a/0x2050 io_uring/io-wq.c:596
 io_wq_worker+0x5a1/0x1370 io_uring/io-wq.c:649
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
 __alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598
 __alloc_pages_node include/linux/gfp.h:238 [inline]
 alloc_pages_node include/linux/gfp.h:261 [inline]
 alloc_slab_page mm/slub.c:2175 [inline]
 allocate_slab mm/slub.c:2338 [inline]
 new_slab+0x2de/0x1400 mm/slub.c:2391
 ___slab_alloc+0x1184/0x33d0 mm/slub.c:3525
 __kmem_cache_alloc_bulk mm/slub.c:4555 [inline]
 kmem_cache_alloc_bulk+0x503/0x13e0 mm/slub.c:4629
 __io_alloc_req_refill+0x248/0x780 io_uring/io_uring.c:1101
 io_alloc_req io_uring/io_uring.h:405 [inline]
 io_submit_sqes+0xaba/0x2fe0 io_uring/io_uring.c:2481
 __do_sys_io_uring_enter io_uring/io_uring.c:3668 [inline]
 __se_sys_io_uring_enter+0x407/0x4400 io_uring/io_uring.c:3603
 __ia32_sys_io_uring_enter+0x11d/0x1a0 io_uring/io_uring.c:3603
 ia32_sys_call+0x2c0/0x40a0 arch/x86/include/generated/asm/syscalls_32.h:427
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0xb4/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x38/0x80 arch/x86/entry/common.c:411
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:449
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

CPU: 1 PID: 20102 Comm: iou-wrk-20100 Tainted: G        W          6.9.0-rc6-syzkaller-00234-g7367539ad4b0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
=====================================================


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