After batched used ring updating was introduced in commit e2b3b35eb9
("vhost_net: batch used ring update in rx"). We tend to batch heads in
vq->heads for more than one packet. But the quota passed to
get_rx_bufs() was not correctly limited, which can result a OOB write
in vq->heads.
headcount = get_rx_bufs(vq, vq->heads + nvq->done_idx,
vhost_len, &in, vq_log, &log,
likely(mergeable) ? UIO_MAXIOV : 1);
UIO_MAXIOV was still used which is wrong since we could have batched
used in vq->heads, this will cause OOB if the next buffer needs more
than 960 (1024 (UIO_MAXIOV) - 64 (VHOST_NET_BATCH)) heads after we've
batched 64 (VHOST_NET_BATCH) heads:
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
=============================================================================
BUG kmalloc-8k (Tainted: G B ): Redzone overwritten
-----------------------------------------------------------------------------
INFO: 0x00000000fd93b7a2-0x00000000f0713384. First byte 0xa9 instead of 0xcc
INFO: Allocated in alloc_pd+0x22/0x60 age=3933677 cpu=2 pid=2674
kmem_cache_alloc_trace+0xbb/0x140
alloc_pd+0x22/0x60
gen8_ppgtt_create+0x11d/0x5f0
i915_ppgtt_create+0x16/0x80
i915_gem_create_context+0x248/0x390
i915_gem_context_create_ioctl+0x4b/0xe0
drm_ioctl_kernel+0xa5/0xf0
drm_ioctl+0x2ed/0x3a0
do_vfs_ioctl+0x9f/0x620
ksys_ioctl+0x6b/0x80
__x64_sys_ioctl+0x11/0x20
do_syscall_64+0x43/0xf0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
INFO: Slab 0x00000000d13e87af objects=3 used=3 fp=0x (null) flags=0x200000000010201
INFO: Object 0x0000000003278802 @offset=17064 fp=0x00000000e2e6652b
Fixing this by allocating UIO_MAXIOV + VHOST_NET_BATCH iovs for
vhost-net. This is done through set the limitation through
vhost_dev_init(), then set_owner can allocate the number of iov in a
per device manner.
This fixes CVE-2018-16880.
Fixes: e2b3b35eb9 ("vhost_net: batch used ring update in rx")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
b46a0bf78a