Re: [syzbot] [virtualization?] KMSAN: uninit-value in virtqueue_add (4)

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jan 01, 2024 at 05:38:24AM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    fbafc3e621c3 Merge tag 'for_linus' of git://git.kernel.org..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=173df3e9e80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e0c7078a6b901aa3
> dashboard link: https://syzkaller.appspot.com/bug?extid=d7521c1e3841ed075a42
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1300b4a1e80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=130b0379e80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/1520f7b6daa4/disk-fbafc3e6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/8b490af009d5/vmlinux-fbafc3e6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/202ca200f4a4/bzImage-fbafc3e6.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d7521c1e3841ed075a42@syzkaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in vring_map_one_sg drivers/virtio/virtio_ring.c:380 [inline]
> BUG: KMSAN: uninit-value in virtqueue_add_split drivers/virtio/virtio_ring.c:614 [inline]
> BUG: KMSAN: uninit-value in virtqueue_add+0x21c6/0x6530 drivers/virtio/virtio_ring.c:2210
>  vring_map_one_sg drivers/virtio/virtio_ring.c:380 [inline]
>  virtqueue_add_split drivers/virtio/virtio_ring.c:614 [inline]
>  virtqueue_add+0x21c6/0x6530 drivers/virtio/virtio_ring.c:2210
>  virtqueue_add_sgs+0x186/0x1a0 drivers/virtio/virtio_ring.c:2244
>  __virtscsi_add_cmd drivers/scsi/virtio_scsi.c:467 [inline]
>  virtscsi_add_cmd+0x838/0xad0 drivers/scsi/virtio_scsi.c:501
>  virtscsi_queuecommand+0x896/0xa60 drivers/scsi/virtio_scsi.c:598
>  scsi_dispatch_cmd drivers/scsi/scsi_lib.c:1516 [inline]
>  scsi_queue_rq+0x4874/0x5790 drivers/scsi/scsi_lib.c:1758
>  blk_mq_dispatch_rq_list+0x13f8/0x3600 block/blk-mq.c:2049
>  __blk_mq_do_dispatch_sched block/blk-mq-sched.c:170 [inline]
>  blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
>  __blk_mq_sched_dispatch_requests+0x10af/0x2500 block/blk-mq-sched.c:309
>  blk_mq_sched_dispatch_requests+0x160/0x2d0 block/blk-mq-sched.c:333
>  blk_mq_run_work_fn+0xd0/0x280 block/blk-mq.c:2434
>  process_one_work kernel/workqueue.c:2627 [inline]
>  process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2700
>  worker_thread+0xf45/0x1490 kernel/workqueue.c:2781
>  kthread+0x3ed/0x540 kernel/kthread.c:388
>  ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
> 
> Uninit was created at:
>  __alloc_pages+0x9a4/0xe00 mm/page_alloc.c:4591
>  alloc_pages_mpol+0x62b/0x9d0 mm/mempolicy.c:2133
>  alloc_pages mm/mempolicy.c:2204 [inline]
>  folio_alloc+0x1da/0x380 mm/mempolicy.c:2211
>  filemap_alloc_folio+0xa5/0x430 mm/filemap.c:974
>  __filemap_get_folio+0xa5a/0x1760 mm/filemap.c:1918
>  ext4_da_write_begin+0x7f8/0xec0 fs/ext4/inode.c:2891
>  generic_perform_write+0x3f5/0xc40 mm/filemap.c:3918
>  ext4_buffered_write_iter+0x564/0xaa0 fs/ext4/file.c:299
>  ext4_file_write_iter+0x20f/0x3460
>  __kernel_write_iter+0x329/0x930 fs/read_write.c:517
>  dump_emit_page fs/coredump.c:888 [inline]
>  dump_user_range+0x593/0xcd0 fs/coredump.c:915
>  elf_core_dump+0x528d/0x5a40 fs/binfmt_elf.c:2077
>  do_coredump+0x32c9/0x4920 fs/coredump.c:764
>  get_signal+0x2185/0x2d10 kernel/signal.c:2890
>  arch_do_signal_or_restart+0x53/0xca0 arch/x86/kernel/signal.c:309
>  exit_to_user_mode_loop+0xe8/0x320 kernel/entry/common.c:168
>  exit_to_user_mode_prepare+0x163/0x220 kernel/entry/common.c:204
>  irqentry_exit_to_user_mode+0xd/0x30 kernel/entry/common.c:309
>  irqentry_exit+0x16/0x40 kernel/entry/common.c:412
>  exc_page_fault+0x246/0x6f0 arch/x86/mm/fault.c:1564
>  asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:570
> 
> Bytes 0-4095 of 4096 are uninitialized
> Memory access of size 4096 starts at ffff88812c79c000
> 
> CPU: 0 PID: 997 Comm: kworker/0:1H Not tainted 6.7.0-rc7-syzkaller-00003-gfbafc3e621c3 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
> Workqueue: kblockd blk_mq_run_work_fn
> =====================================================
> 
> 
> ---
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> 
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> If you want to undo deduplication, reply with:
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