udmabuf: add back sanity check

kraxel · torvalds · commit 05b252cccb2e · 2022-06-20T08:38:29.000-05:00
Check vm_fault->pgoff before using it. When we removed the warning, we also removed the check. Fixes: 7b26e4e ("udmabuf: drop WARN_ON() check.") Reported-by: zdi-disclosures@trendmicro.com Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c
@@ -32,8 +32,11 @@ 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;
 }

Original file line number	Diff line number	Diff line change
`@@ -32,8 +32,11 @@ static vm_fault_t udmabuf_vm_fault(struct vm_fault *vmf)`
`32`	`32`	`{`
`33`	`33`	`struct vm_area_struct *vma = vmf->vma;`
`34`	`34`	`struct udmabuf *ubuf = vma->vm_private_data;`
	`35`	`+ pgoff_t pgoff = vmf->pgoff;`
`35`	`36`
`36`		`- vmf->page = ubuf->pages[vmf->pgoff];`
	`37`	`+ if (pgoff >= ubuf->pagecount)`
	`38`	`+ return VM_FAULT_SIGBUS;`
	`39`	`+ vmf->page = ubuf->pages[pgoff];`
`37`	`40`	`get_page(vmf->page);`
`38`	`41`	`return 0;`
`39`	`42`	`}`