linux-kernel - [PATCH] vfio: Fix double free for caps->buf

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Date:   Tue, 28 Jun 2022 13:07:11 +0800
From:   Schspa Shi <schspa@...il.com>
To:     alex.williamson@...hat.com, cohuck@...hat.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        zhaohui.shi@...izon.ai, Schspa Shi <schspa@...il.com>
Subject: [PATCH] vfio: Fix double free for caps->buf

There is a double free, if vfio_iommu_dma_avail_build_caps
calls failed.

The following call path will call vfio_info_cap_add multiple times

vfio_iommu_type1_get_info
	if (!ret)
		ret = vfio_iommu_dma_avail_build_caps(iommu, &caps);

	if (!ret)
		ret = vfio_iommu_iova_build_caps(iommu, &caps);

If krealloc failed on vfio_info_cap_add, there will be a double free.

Signed-off-by: Schspa Shi <schspa@...il.com>
---
 drivers/vfio/vfio.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 61e71c1154be..a0fb93866f61 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1812,6 +1812,7 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
 	buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
 	if (!buf) {
 		kfree(caps->buf);
+		caps->buf = NULL;
 		caps->size = 0;
 		return ERR_PTR(-ENOMEM);
 	}
-- 
2.29.0