linux-kernel - [PATCH] filemap: fix error pointer dereference in filemap

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Message-Id: <20240716022518.430237-1-make24@iscas.ac.cn>
Date: Tue, 16 Jul 2024 10:25:18 +0800
From: Ma Ke <make24@...as.ac.cn>
To: willy@...radead.org,
	akpm@...ux-foundation.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Ma Ke <make24@...as.ac.cn>
Subject: [PATCH] filemap: fix error pointer dereference in filemap_fault()

This code calls folio_put() on an error pointer which will lead to a
crash.  Check for both error pointers and NULL pointers before calling
folio_put().

Fixes: 38a55db9877c ("filemap: Handle error return from __filemap_get_folio()")
Signed-off-by: Ma Ke <make24@...as.ac.cn>
---
 mm/filemap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 657bcd887fdb..cd26617d8987 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3420,7 +3420,7 @@ vm_fault_t filemap_fault(struct vm_fault *vmf)
 	 * re-find the vma and come back and find our hopefully still populated
 	 * page.
 	 */
-	if (!IS_ERR(folio))
+	if (!IS_ERR_OR_NULL(folio))
 		folio_put(folio);
 	if (mapping_locked)
 		filemap_invalidate_unlock_shared(mapping);
-- 
2.25.1