[syzbot] [io-uring?] KMSAN: uninit-value in io_rw_fail (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1743d3e4180000
kernel config: https://syzkaller.appspot.com/x/.config?x=656820e61b758b15
dashboard link: https://syzkaller.appspot.com/bug?extid=0198afa90d8c29ef9557
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d9f2f4b065/disk-9f8413c4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cbc68430d9c6/vmlinux-9f8413c4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9740ad9fc172/bzImage-9f8413c4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0198af...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in io_fixup_rw_res io_uring/rw.c:311 [inline]
BUG: KMSAN: uninit-value in io_rw_fail+0x1a7/0x1b0 io_uring/rw.c:1099
io_fixup_rw_res io_uring/rw.c:311 [inline]
io_rw_fail+0x1a7/0x1b0 io_uring/rw.c:1099
io_req_defer_failed+0x217/0x3e0 io_uring/io_uring.c:1065
io_queue_sqe_fallback+0x1f4/0x260 io_uring/io_uring.c:2100
io_submit_state_end io_uring/io_uring.c:2345 [inline]
io_submit_sqes+0x2b85/0x2ff0 io_uring/io_uring.c:2463
__do_sys_io_uring_enter io_uring/io_uring.c:3712 [inline]
__se_sys_io_uring_enter+0x40c/0x42d0 io_uring/io_uring.c:3647
__x64_sys_io_uring_enter+0x11b/0x1a0 io_uring/io_uring.c:3647
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
slab_alloc_node mm/slub.c:3478 [inline]
__kmem_cache_alloc_node+0x5c9/0x970 mm/slub.c:3517
__do_kmalloc_node mm/slab_common.c:1006 [inline]
__kmalloc+0x121/0x3c0 mm/slab_common.c:1020
kmalloc include/linux/slab.h:604 [inline]
io_alloc_async_data io_uring/io_uring.c:1780 [inline]
io_req_prep_async+0x384/0x5a0 io_uring/io_uring.c:1801
io_queue_sqe_fallback+0x95/0x260 io_uring/io_uring.c:2097
io_submit_state_end io_uring/io_uring.c:2345 [inline]
io_submit_sqes+0x2b85/0x2ff0 io_uring/io_uring.c:2463
__do_sys_io_uring_enter io_uring/io_uring.c:3712 [inline]
__se_sys_io_uring_enter+0x40c/0x42d0 io_uring/io_uring.c:3647
__x64_sys_io_uring_enter+0x11b/0x1a0 io_uring/io_uring.c:3647
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 5401 Comm: syz-executor.4 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================


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[Jens Axboe]

On 2/9/24 3:10 PM, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1743d3e4180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=656820e61b758b15
> dashboard link: https://syzkaller.appspot.com/bug?extid=0198afa90d8c29ef9557
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

This was fixed a while back, not sure why an old kernel is being tested. But
in any case, the result of this was just garbage in cqe->res for a request
that was prematurely errored. Nothing to worry about. In any case:

#syz fix: io_uring/rw: ensure io->bytes_done is always initialized

--
Jens Axboe

[Alexander Potapenko]

> This was fixed a while back, not sure why an old kernel is being tested. But
> in any case, the result of this was just garbage in cqe->res for a request
> that was prematurely errored. Nothing to worry about. In any case:

Unfortunately KMSAN is broken at head, we're waiting for
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=558c04d9535d9d8911162db4d0d758f8f4cda37b
to reach mainline.