[syzbot] KMSAN: uninit-value in io_fallback_req_func

[syzbot] KMSAN: uninit-value in io_fallback_req_func

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    33d9269ef6e0 Revert "kernel: kmsan: don't instrument stack..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=12a4e62cf00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f8f2668b971cd508
dashboard link: https://syzkaller.appspot.com/bug?extid=5ca552d10251920ab7e2
compiler:       clang version 14.0.0 (/usr/local/google/src/llvm-git-monorepo 2b554920f11c8b763cd9ed9003f4e19b919b8e1f), GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11a2e148f00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1332bce8f00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5ca552d10251920ab7e2@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in io_fallback_req_func+0x218/0x5f7 fs/io_uring.c:1399
 io_fallback_req_func+0x218/0x5f7 fs/io_uring.c:1399
 process_one_work+0xdb6/0x1820 kernel/workqueue.c:2307
 worker_thread+0x10b3/0x21e0 kernel/workqueue.c:2454
 kthread+0x3c7/0x500 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:737 [inline]
 kmem_cache_alloc_bulk+0xe98/0x1530 mm/slub.c:3744
 __io_alloc_req_refill+0x482/0x867 fs/io_uring.c:2072
 io_alloc_req_refill fs/io_uring.c:2098 [inline]
 io_submit_sqes+0x7d4/0x1a00 fs/io_uring.c:7441
 __do_sys_io_uring_enter fs/io_uring.c:10162 [inline]
 __se_sys_io_uring_enter+0x62f/0x23a0 fs/io_uring.c:10104
 __x64_sys_io_uring_enter+0x19d/0x200 fs/io_uring.c:10104
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x44/0xae

CPU: 0 PID: 3552 Comm: kworker/0:4 Not tainted 5.17.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Comput


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