[PATCH 5.10 044/102] udmabuf: add back sanity check

[Greg Kroah-Hartman]

From: Gerd Hoffmann <kraxel@xxxxxxxxxx>

[ Upstream commit 05b252cccb2e5c3f56119d25de684b4f810ba40a ]

Check vm_fault->pgoff before using it.  When we removed the warning, we
also removed the check.

Fixes: 7b26e4e2119d ("udmabuf: drop WARN_ON() check.")
Reported-by: zdi-disclosures@xxxxxxxxxxxxxx
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/dma-buf/udmabuf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
index cfbf10128aae..2e3b76519b49 100644
--- a/drivers/dma-buf/udmabuf.c
+++ b/drivers/dma-buf/udmabuf.c
@@ -26,8 +26,11 @@ 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;
 
-	vmf->page = ubuf->pages[vmf->pgoff];
+	if (pgoff >= ubuf->pagecount)
+		return VM_FAULT_SIGBUS;
+	vmf->page = ubuf->pages[pgoff];
 	get_page(vmf->page);
 	return 0;
 }
-- 
2.35.1