linux-kernel - [RFC][PATCH 4/5] shmem: Avoid segfault in shmem_read_mapping_page

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Date:   Fri, 12 Nov 2021 13:44:10 +0100
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <ebiggers@...nel.org>, <tytso@....edu>, <corbet@....net>,
        <viro@...iv.linux.org.uk>, <hughd@...gle.com>,
        <akpm@...ux-foundation.org>
CC:     <linux-fscrypt@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-mm@...ck.org>,
        <linux-integrity@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [RFC][PATCH 4/5] shmem: Avoid segfault in shmem_read_mapping_page_gfp()

Check the hwpoison page flag only if the page is valid in
shmem_read_mapping_page_gfp(). The PageHWPoison() macro tries to access
the page flags and cannot work on an error pointer.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
---
 mm/shmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 23c91a8beb78..427863cbf0dc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4222,7 +4222,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 	else
 		unlock_page(page);
 
-	if (PageHWPoison(page))
+	if (!IS_ERR(page) && PageHWPoison(page))
 		page = ERR_PTR(-EIO);
 
 	return page;
-- 
2.32.0