[PATCH 6.4 01/13] xtensa: fix lock_mm_and_find_vma in case VMA not found

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Max Filippov <jcmvbkbc@gmail.com>

commit 03f889378f33aa9a9d8e5f49ba94134cf6158090 upstream.

MMU version of lock_mm_and_find_vma releases the mm lock before
returning when VMA is not found. Do the same in noMMU version.
This fixes hang on an attempt to handle protection fault.

Fixes: d85a143b69ab ("xtensa: fix NOMMU build with lock_mm_and_find_vma() conversion")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/nommu.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -637,8 +637,13 @@ EXPORT_SYMBOL(find_vma);
 struct vm_area_struct *lock_mm_and_find_vma(struct mm_struct *mm,
 			unsigned long addr, struct pt_regs *regs)
 {
+	struct vm_area_struct *vma;
+
 	mmap_read_lock(mm);
-	return vma_lookup(mm, addr);
+	vma = vma_lookup(mm, addr);
+	if (!vma)
+		mmap_read_unlock(mm);
+	return vma;
 }
 
 /*