[PATCH 5.15.y 4/4] VDUSE: avoid leaking information to userspace

[Sasha Levin <sashal@kernel.org>]

From: Jason Wang <jasowang@redhat.com>

[ Upstream commit 9c1523803445ee0348f62b77793266dd981596e0 ]

The bounceing is not necessarily page aligned, so current VDUSE can
leak kernel information through mapping bounce pages to
userspace. Allocate bounce pages with __GFP_ZERO to avoid leaking
information to userspace.

Fixes: 8c773d53fb7b ("vduse: Implement an MMU-based software IOTLB")
Cc: stable@vger.kernel.org
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Xie Yongji <xieyongji@bytedance.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20260130050750.4050-1-jasowang@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/vdpa/vdpa_user/iova_domain.c | 2 +-
 drivers/vdpa/vdpa_user/vduse_dev.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c
index 26f3fb5e0b0677..783319f1607619 100644
--- a/drivers/vdpa/vdpa_user/iova_domain.c
+++ b/drivers/vdpa/vdpa_user/iova_domain.c
@@ -124,7 +124,7 @@ static int vduse_domain_map_bounce_page(struct vduse_iova_domain *domain,
 		if (!map->bounce_page) {
 			head_map = &domain->bounce_maps[(iova & PAGE_MASK) >> BOUNCE_MAP_SHIFT];
 			if (!head_map->bounce_page) {
-				tmp_page = alloc_page(GFP_ATOMIC);
+				tmp_page = alloc_page(GFP_ATOMIC | __GFP_ZERO);
 				if (!tmp_page)
 					return -ENOMEM;
 				if (cmpxchg(&head_map->bounce_page, NULL, tmp_page))
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 8f05d1bfdb1076..ce84b0fb8428d3 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -776,7 +776,7 @@ static void *vduse_dev_alloc_coherent(struct device *dev, size_t size,
 
 	*dma_addr = DMA_MAPPING_ERROR;
 
-	addr = alloc_pages_exact(size, flag);
+	addr = alloc_pages_exact(size, flag | __GFP_ZERO);
 	if (!addr)
 		return NULL;
 
-- 
2.53.0