From:   Roberto Sassu <roberto.sassu@huawei.com>
To:     <ebiggers@kernel.org>, <tytso@mit.edu>, <corbet@lwn.net>,
        <viro@zeniv.linux.org.uk>, <hughd@google.com>,
        <akpm@linux-foundation.org>
CC:     <linux-fscrypt@vger.kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-fsdevel@vger.kernel.org>, <linux-mm@kvack.org>,
        <linux-integrity@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        Roberto Sassu <roberto.sassu@huawei.com>
Subject: [RFC][PATCH 4/5] shmem: Avoid segfault in shmem_read_mapping_page_gfp()
Date:   Fri, 12 Nov 2021 13:44:10 +0100
Message-ID: <20211112124411.1948809-5-roberto.sassu@huawei.com>
In-Reply-To: <20211112124411.1948809-1-roberto.sassu@huawei.com>
References: <20211112124411.1948809-1-roberto.sassu@huawei.com>
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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@huawei.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