UPSTREAM: mm/mprotect: replace can_modify_mm with can_modify_vma

Avoid taking an extra trip down the mmap tree by checking the vmas
directly.  mprotect (per POSIX) tolerates partial failure.

Link: https://lkml.kernel.org/r/[email protected]
Change-Id: I519796354b9c88444854e53a8eea105e3e824010
Signed-off-by: Pedro Falcato <[email protected]>
Reviewed-by: Liam R. Howlett <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Cc: Jeff Xu <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
(cherry picked from commit 4a2dd02)

Author: heatd

mm/mprotect.c

@@ -587,6 +587,9 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
 	pgoff_t pgoff;
 	int error;
 
+	if (!can_modify_vma(vma))
+		return -EPERM;
+
 	if (newflags == oldflags) {
 		*pprev = vma;
 		return 0;
@@ -756,15 +759,6 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		}
 	}
 
-	/*
-	 * checking if memory is sealed.
-	 * can_modify_mm assumes we have acquired the lock on MM.
-	 */
-	if (unlikely(!can_modify_mm(current->mm, start, end))) {
-		error = -EPERM;
-		goto out;
-	}
-
 	prev = vma_prev(&vmi);
 	if (start > vma->vm_start)
 		prev = vma;