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Date: Wed, 11 Apr 2018 10:35:40 +0800 From: Stefan Hajnoczi <stefanha@...hat.com> To: virtualization@...ts.linux-foundation.org Cc: Linus Torvalds <torvalds@...ux-foundation.org>, jasowang@...hat.com, mst@...hat.com, netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, Stefan Hajnoczi <stefanha@...hat.com> Subject: [PATCH v3 1/2] vhost: fix vhost_vq_access_ok() log check Commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ("vhost: validate log when IOTLB is enabled") introduced a regression. The logic was originally: if (vq->iotlb) return 1; return A && B; After the patch the short-circuit logic for A was inverted: if (A || vq->iotlb) return A; return B; This patch fixes the regression by rewriting the checks in the obvious way, no longer returning A when vq->iotlb is non-NULL (which is hard to understand). Reported-by: syzbot+65a84dde0214b0387ccd@...kaller.appspotmail.com Cc: Jason Wang <jasowang@...hat.com> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com> --- drivers/vhost/vhost.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index bec722e41f58..fc805b7fad9d 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1244,10 +1244,12 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq, /* Caller should have vq mutex and device mutex */ int vhost_vq_access_ok(struct vhost_virtqueue *vq) { - int ret = vq_log_access_ok(vq, vq->log_base); + if (!vq_log_access_ok(vq, vq->log_base)) + return 0; - if (ret || vq->iotlb) - return ret; + /* Access validation occurs at prefetch time with IOTLB */ + if (vq->iotlb) + return 1; return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used); } -- 2.14.3
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