[PATCH v6.6] udmabuf: use vmf_insert_pfn and VM_PFNMAP for handling mmap

[Andrey Kalachev]

From: Vivek Kasireddy <vivek.kasireddy at intel.com>

[ Upstream commit 7d79cd784470395539bda91bf0b3505ff5b2ab6d ]

Add VM_PFNMAP to vm_flags in the mmap handler to ensure that the mappings
would be managed without using struct page.

And, in the vm_fault handler, use vmf_insert_pfn to share the page's pfn
to userspace instead of directly sharing the page (via struct page *).

Link: https://lkml.kernel.org/r/20240624063952.1572359-6-vivek.kasireddy@intel.com
Signed-off-by: Vivek Kasireddy <vivek.kasireddy at intel.com>
Suggested-by: David Hildenbrand <david at redhat.com>
Acked-by: David Hildenbrand <david at redhat.com>
Acked-by: Dave Airlie <airlied at redhat.com>
Acked-by: Gerd Hoffmann <kraxel at redhat.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Hugh Dickins <hughd at google.com>
Cc: Peter Xu <peterx at redhat.com>
Cc: Jason Gunthorpe <jgg at nvidia.com>
Cc: Dongwon Kim <dongwon.kim at intel.com>
Cc: Junxiao Chang <junxiao.chang at intel.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Christoph Hellwig <hch at infradead.org>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Matthew Wilcox (Oracle) <willy at infradead.org>
Cc: Mike Kravetz <mike.kravetz at oracle.com>
Cc: Oscar Salvador <osalvador at suse.de>
Cc: Shuah Khan <shuah at kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Reported-by: syzbot+3d218f7b6c5511a83a79 at syzkaller.appspotmail.com
---
 drivers/dma-buf/udmabuf.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index c40645999648..820c993c8659 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -35,12 +35,13 @@ static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)
 	struct vm_area_struct *vma = vmf->vma;
 	struct udmabuf *ubuf = vma->vm_private_data;
 	pgoff_t pgoff = vmf->pgoff;
+	unsigned long pfn;
 
 	if (pgoff >= ubuf->pagecount)
 		return VM_FAULT_SIGBUS;
-	vmf->page = ubuf->pages[pgoff];
-	get_page(vmf->page);
-	return 0;
+
+	pfn = page_to_pfn(ubuf->pages[pgoff]);
+	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
 static const struct vm_operations_struct udmabuf_vm_ops = {
@@ -56,6 +57,7 @@ static int mmap_udmabuf(struct dma_buf *buf, struct vm_area_struct *vma)
 
 	vma->vm_ops = &udmabuf_vm_ops;
 	vma->vm_private_data = ubuf;
+	vm_flags_set(vma, VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP);
 	return 0;
 }
 
-- 
2.30.2