linux-kernel - [PATCH] xtensa: fix lock_mm_and_find

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Date:   Sat,  1 Jul 2023 03:31:55 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Chris Zankel <chris@...kel.net>,
        Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Max Filippov <jcmvbkbc@...il.com>
Subject: [PATCH] xtensa: fix lock_mm_and_find_vma in case VMA not found

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@...il.com>
---
 mm/nommu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index fdc392735ec6..c072a660ec2c 100644
--- 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;
 }
 
 /*
-- 
2.30.2