linux-kernel - [PATCH v1] Fix NULL pointer dereference in read_cache

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Message-ID: <20240929230548.370027-3-gianf.trad@gmail.com>
Date: Mon, 30 Sep 2024 01:05:50 +0200
From: Gianfranco Trad <gianf.trad@...il.com>
To: willy@...radead.org,
	akpm@...ux-foundation.org
Cc: linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	skhan@...uxfoundation.org,
	Gianfranco Trad <gianf.trad@...il.com>,
	syzbot+4089e577072948ac5531@...kaller.appspotmail.com
Subject: [PATCH v1] Fix NULL pointer dereference in read_cache_folio

Add check on filler to prevent NULL pointer dereference condition in
read_cache_folio[1].

[1] https://syzkaller.appspot.com/bug?extid=4089e577072948ac5531

Reported-by: syzbot+4089e577072948ac5531@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=4089e577072948ac5531
Tested-by: syzbot+4089e577072948ac5531@...kaller.appspotmail.com
Signed-off-by: Gianfranco Trad <gianf.trad@...il.com>
---
 mm/filemap.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 4f3753f0a158..960f389e2d3b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2360,7 +2360,10 @@ static int filemap_read_folio(struct file *file, filler_t filler,
 	/* Start the actual read. The read will unlock the page. */
 	if (unlikely(workingset))
 		psi_memstall_enter(&pflags);
-	error = filler(file, folio);
+	if (filler)
+		error = filler(file, folio);
+	else
+		return -EIO;
 	if (unlikely(workingset))
 		psi_memstall_leave(&pflags);
 	if (error)
-- 
2.43.0