Re: [syzbot] [io-uring] KMSAN: uninit-value in putname

[Jens Axboe <axboe@kernel.dk>]

On 4/28/25 3:38 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a33b5a08cbbd Merge tag 'sched_ext-for-6.15-rc3-fixes' of g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13f77fac580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=fca45111586bf9a6
> dashboard link: https://syzkaller.appspot.com/bug?extid=9b12063ba8beec94f5b8
> compiler:       Debian clang version 15.0.6, Debian LLD 15.0.6
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/e23fd3b01d5c/disk-a33b5a08.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d39e4ee184b3/vmlinux-a33b5a08.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/d4117549249f/bzImage-a33b5a08.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9b12063ba8beec94f5b8@syzkaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in putname+0x8f/0x1d0 fs/namei.c:285
>  putname+0x8f/0x1d0 fs/namei.c:285
>  io_statx_cleanup+0x57/0x80 io_uring/statx.c:70
>  io_clean_op+0x154/0x690 io_uring/io_uring.c:411
>  io_free_batch_list io_uring/io_uring.c:1424 [inline]
>  __io_submit_flush_completions+0x1b00/0x1cd0 io_uring/io_uring.c:1465
>  io_submit_flush_completions io_uring/io_uring.h:165 [inline]
>  io_fallback_req_func+0x28e/0x4e0 io_uring/io_uring.c:260
>  process_one_work kernel/workqueue.c:3238 [inline]
>  process_scheduled_works+0xc1d/0x1e80 kernel/workqueue.c:3319
>  worker_thread+0xea3/0x1500 kernel/workqueue.c:3400
>  kthread+0x6ce/0xf10 kernel/kthread.c:464
>  ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:153
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> 
> Uninit was created at:
>  slab_post_alloc_hook mm/slub.c:4167 [inline]
>  slab_alloc_node mm/slub.c:4210 [inline]
>  kmem_cache_alloc_noprof+0x926/0xe20 mm/slub.c:4217
>  getname_flags+0x102/0xa20 fs/namei.c:146
>  getname_uflags+0x3a/0x50 fs/namei.c:222
>  io_statx_prep+0x26f/0x430 io_uring/statx.c:39
>  io_init_req io_uring/io_uring.c:2140 [inline]
>  io_submit_sqe io_uring/io_uring.c:2187 [inline]
>  io_submit_sqes+0x10c1/0x2f50 io_uring/io_uring.c:2342
>  __do_sys_io_uring_enter io_uring/io_uring.c:3402 [inline]
>  __se_sys_io_uring_enter+0x410/0x4db0 io_uring/io_uring.c:3336
>  __x64_sys_io_uring_enter+0x11f/0x1a0 io_uring/io_uring.c:3336
>  x64_sys_call+0x2dbb/0x3c80 arch/x86/include/generated/asm/syscalls_64.h:427
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xcd/0x1b0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> CPU: 0 UID: 0 PID: 10442 Comm: kworker/0:3 Tainted: G        W           6.15.0-rc3-syzkaller-00008-ga33b5a08cbbd #0 PREEMPT(undef) 
> Tainted: [W]=WARN
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
> Workqueue: events io_fallback_req_func
> =====================================================

I took a look at this and there should be no way for this to happen.
Then I looked at the dmesg log, and there's a ton of failures prior
to this, including what looks like memory corruption due to UAF
on other pages.

#syz invalid

-- 
Jens Axboe