From 498e8bf51c633cc4496343e6113f340f8e9301ae Mon Sep 17 00:00:00 2001 From: Alexey Khoroshilov Date: Fri, 6 Jul 2018 23:50:06 +0300 Subject: [PATCH] sample: vfio-mdev: avoid deadlock in mdev_access() mdev_access() calls mbochs_get_page() with mdev_state->ops_lock held, while mbochs_get_page() locks the mutex by itself. It leads to unavoidable deadlock. Found by Linux Driver Verification project (linuxtesting.org). Signed-off-by: Alexey Khoroshilov Signed-off-by: Alex Williamson --- samples/vfio-mdev/mbochs.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c index d5d5a499160c..2535c3677c7b 100644 --- a/samples/vfio-mdev/mbochs.c +++ b/samples/vfio-mdev/mbochs.c @@ -178,6 +178,8 @@ static const char *vbe_name(u32 index) return "(invalid)"; } +static struct page *__mbochs_get_page(struct mdev_state *mdev_state, + pgoff_t pgoff); static struct page *mbochs_get_page(struct mdev_state *mdev_state, pgoff_t pgoff); @@ -394,7 +396,7 @@ static ssize_t mdev_access(struct mdev_device *mdev, char *buf, size_t count, MBOCHS_MEMORY_BAR_OFFSET + mdev_state->memsize) { pos -= MBOCHS_MMIO_BAR_OFFSET; poff = pos & ~PAGE_MASK; - pg = mbochs_get_page(mdev_state, pos >> PAGE_SHIFT); + pg = __mbochs_get_page(mdev_state, pos >> PAGE_SHIFT); map = kmap(pg); if (is_write) memcpy(map + poff, buf, count);