linux-kernel - [PATCH 5.15 01/72] fscache_cookie_enabled: check cookie is valid before accessing it

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Message-Id: <20220110071821.549570773@linuxfoundation.org>
Date:   Mon, 10 Jan 2022 08:22:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Jeffrey E Altman <jaltman@...istor.com>
Subject: [PATCH 5.15 01/72] fscache_cookie_enabled: check cookie is valid before accessing it

From: Dominique Martinet <asmadeus@...ewreck.org>

commit 0dc54bd4d6e03be1f0b678c4297170b79f1a44ab upstream.

fscache_cookie_enabled() could be called on NULL cookies and cause a
null pointer dereference when accessing cookie flags: just make sure
the cookie is valid first

Suggested-by: David Howells <dhowells@...hat.com>
Acked-by: David Howells <dhowells@...hat.com>
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Cc: Jeffrey E Altman <jaltman@...istor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 include/linux/fscache.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -167,7 +167,7 @@ struct fscache_cookie {
 
 static inline bool fscache_cookie_enabled(struct fscache_cookie *cookie)
 {
-	return test_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
+	return fscache_cookie_valid(cookie) && test_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 }
 
 /*