From 7e9480b480a57fb4ef2e4d2c2cddbb1a31d56b33 Mon Sep 17 00:00:00 2001 From: yongduan Date: Wed, 11 Sep 2019 17:44:24 +0800 Subject: [PATCH] vhost: make sure log_num < in_num commit 060423bfdee3f8bc6e2c1bac97de24d5415e2bc4 upstream. The code assumes log_num < in_num everywhere, and that is true as long as in_num is incremented by descriptor iov count, and log_num by 1. However this breaks if there's a zero sized descriptor. As a result, if a malicious guest creates a vring desc with desc.len = 0, it may cause the host kernel to crash by overflowing the log array. This bug can be triggered during the VM migration. There's no need to log when desc.len = 0, so just don't increment log_num in this case. Fixes: 3a4d5c94e959 ("vhost_net: a kernel-level virtio server") Cc: stable@vger.kernel.org Reviewed-by: Lidong Chen Signed-off-by: ruippan Signed-off-by: yongduan Acked-by: Michael S. Tsirkin Reviewed-by: Tyler Hicks Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman --- drivers/vhost/vhost.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 88fa81c482e8..3d7bea15c57b 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2066,7 +2066,7 @@ static int get_indirect(struct vhost_virtqueue *vq, /* If this is an input descriptor, increment that count. */ if (access == VHOST_ACCESS_WO) { *in_num += ret; - if (unlikely(log)) { + if (unlikely(log && ret)) { log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); log[*log_num].len = vhost32_to_cpu(vq, desc.len); ++*log_num; @@ -2209,7 +2209,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq, /* If this is an input descriptor, * increment that count. */ *in_num += ret; - if (unlikely(log)) { + if (unlikely(log && ret)) { log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); log[*log_num].len = vhost32_to_cpu(vq, desc.len); ++*log_num; -- 2.20.1