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 <khoroshilov@ispras.ru> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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@ -178,6 +178,8 @@ static const char *vbe_name(u32 index)
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return "(invalid)";
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return "(invalid)";
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}
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}
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static struct page *__mbochs_get_page(struct mdev_state *mdev_state,
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pgoff_t pgoff);
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static struct page *mbochs_get_page(struct mdev_state *mdev_state,
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static struct page *mbochs_get_page(struct mdev_state *mdev_state,
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pgoff_t pgoff);
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pgoff_t pgoff);
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@ -394,7 +396,7 @@ static ssize_t mdev_access(struct mdev_device *mdev, char *buf, size_t count,
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MBOCHS_MEMORY_BAR_OFFSET + mdev_state->memsize) {
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MBOCHS_MEMORY_BAR_OFFSET + mdev_state->memsize) {
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pos -= MBOCHS_MMIO_BAR_OFFSET;
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pos -= MBOCHS_MMIO_BAR_OFFSET;
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poff = pos & ~PAGE_MASK;
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poff = pos & ~PAGE_MASK;
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pg = mbochs_get_page(mdev_state, pos >> PAGE_SHIFT);
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pg = __mbochs_get_page(mdev_state, pos >> PAGE_SHIFT);
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map = kmap(pg);
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map = kmap(pg);
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if (is_write)
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if (is_write)
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memcpy(map + poff, buf, count);
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memcpy(map + poff, buf, count);
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