FAILED: patch "[PATCH] vduse: fix VA/PA confusion in the coherent page fault path" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x bb2e6f166547838fd7c320b01c90918b736f76e2
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109202245-failed-5.15-bb2e6f166547@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From bb2e6f166547838fd7c320b01c90918b736f76e2 Mon Sep 17 00:00:00 2001
From: "chenglong.ma" <longpareto@gmail.com>
Date: Mon, 2 Nov 2026 12:08:55 -0500
Subject: [PATCH] vduse: fix VA/PA confusion in the coherent page fault path

vduse_domain_get_coherent_page() assumes that iotlb entries above
bounce_size were installed by vduse_domain_alloc_coherent(), so it
treats map->addr as a physical address. But vduse registers with
use_va = true, and when the device is bound to vhost_vdpa,
vhost_vdpa_va_map() stores a userspace virtual address in map->addr,
which vduse_domain_set_map() then copies into the same iotlb. A
process holding the domain file descriptor across a rebind can
therefore fault in an arbitrary physical page with read/write
access, ignoring the entry permissions.

Additionally, since the domain file mmap lacks VM_IO, the domain
file itself can be mapped and passed to vhost_vdpa_va_map(),
producing self-referential entries that bypass the coherent path
check.

To fix, only translate entries whose backing file is the domain
file itself in vduse_domain_get_coherent_page(), reject such
entries in vduse_domain_set_map() since only external mappings
should be imported, and set VM_IO on the domain file mmap so
vhost_vdpa_va_map() refuses to map it in the first place.

Fixes: 8c773d53fb7b ("vduse: Implement an MMU-based software IOTLB")
Cc: Xie Yongji <xieyongji@bytedance.com>
Cc: stable@vger.kernel.org
Reported-by: chenglong.ma <longpareto@gmail.com>
Signed-off-by: chenglong.ma <longpareto@gmail.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Co-Authored-By: Claude Code <noreply@anthropic.com>
---
 drivers/vdpa/vdpa_user/iova_domain.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c
index b6c958224b7ce..28a977248a0d3 100644
--- a/drivers/vdpa/vdpa_user/iova_domain.c
+++ b/drivers/vdpa/vdpa_user/iova_domain.c
@@ -76,6 +76,10 @@ int vduse_domain_set_map(struct vduse_iova_domain *domain,
 	for (map = vhost_iotlb_itree_first(iotlb, start, last); map;
 	     map = vhost_iotlb_itree_next(map, start, last)) {
 		map_file = (struct vdpa_map_file *)map->opaque;
+		if (!map_file || map_file->file == domain->file) {
+			ret = -EINVAL;
+			goto err;
+		}
 		ret = vduse_iotlb_add_range(domain, map->start, map->last,
 					    map->addr, map->perm,
 					    map_file->file,
@@ -226,6 +230,7 @@ vduse_domain_get_coherent_page(struct vduse_iova_domain *domain, u64 iova)
 {
 	u64 start = iova & PAGE_MASK;
 	u64 last = start + PAGE_SIZE - 1;
+	struct vdpa_map_file *map_file;
 	struct vhost_iotlb_map *map;
 	struct page *page = NULL;
 
@@ -234,6 +239,10 @@ vduse_domain_get_coherent_page(struct vduse_iova_domain *domain, u64 iova)
 	if (!map)
 		goto out;
 
+	map_file = (struct vdpa_map_file *)map->opaque;
+	if (!map_file || map_file->file != domain->file)
+		goto out;
+
 	page = pfn_to_page((map->addr + iova - map->start) >> PAGE_SHIFT);
 	get_page(page);
 out:
@@ -579,7 +588,7 @@ static int vduse_domain_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct vduse_iova_domain *domain = file->private_data;
 
-	vm_flags_set(vma, VM_DONTDUMP | VM_DONTEXPAND);
+	vm_flags_set(vma, VM_IO | VM_DONTDUMP | VM_DONTEXPAND);
 	vma->vm_private_data = domain;
 	vma->vm_ops = &vduse_domain_mmap_ops;
 
-- 
2.53.0