e2ae38cf3d
In vhost_iotlb_add_range_ctx(), range size can overflow to 0 when start is 0 and last is ULONG_MAX. One instance where it can happen is when userspace sends an IOTLB message with iova=size=uaddr=0 (vhost_process_iotlb_msg). So, an entry with size = 0, start = 0, last = ULONG_MAX ends up in the iotlb. Next time a packet is sent, iotlb_access_ok() loops indefinitely due to that erroneous entry. Call Trace: <TASK> iotlb_access_ok+0x21b/0x3e0 drivers/vhost/vhost.c:1340 vq_meta_prefetch+0xbc/0x280 drivers/vhost/vhost.c:1366 vhost_transport_do_send_pkt+0xe0/0xfd0 drivers/vhost/vsock.c:104 vhost_worker+0x23d/0x3d0 drivers/vhost/vhost.c:372 kthread+0x2e9/0x3a0 kernel/kthread.c:377 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 </TASK> Reported by syzbot at: https://syzkaller.appspot.com/bug?extid=0abd373e2e50d704db87 To fix this, do two things: 1. Return -EINVAL in vhost_chr_write_iter() when userspace asks to map a range with size 0. 2. Fix vhost_iotlb_add_range_ctx() to handle the range [0, ULONG_MAX] by splitting it into two entries. Fixes: 0bbe30668d89e ("vhost: factor out IOTLB") Reported-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com Tested-by: syzbot+0abd373e2e50d704db87@syzkaller.appspotmail.com Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com> Link: https://lore.kernel.org/r/20220305095525.5145-1-mail@anirudhrb.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.