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From: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
	syzbot <syzbot+756199124937b31a9b7e@syzkaller.appspotmail.com>
Subject: [PATCH] fat: Fix fat_ra_init() for data clusters == 0
Date: Sat, 11 Jul 2020 20:28:31 +0900	[thread overview]
Message-ID: <87mu462sv4.fsf@mail.parknet.co.jp> (raw)
In-Reply-To: <000000000000ebc53005aa18a1a5@google.com> (syzbot's message of "Fri, 10 Jul 2020 09:14:16 -0700")

If data clusters == 0, fat_ra_init() calls the ->ent_blocknr() for the
cluster beyond ->max_clusters.

This checks the limit before initialization to suppress the warning.

Reported-by: syzbot+756199124937b31a9b7e@syzkaller.appspotmail.com
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
---
 fs/fat/fatent.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index bbfe18c..f7e3304 100644
--- a/fs/fat/fatent.c	2020-07-11 19:58:41.903092419 +0900
+++ b/fs/fat/fatent.c	2020-07-11 19:58:51.545948758 +0900
@@ -657,6 +657,9 @@ static void fat_ra_init(struct super_blo
 	unsigned long ra_pages = sb->s_bdi->ra_pages;
 	unsigned int reada_blocks;
 
+	if (fatent->entry >= ent_limit)
+		return;
+
 	if (ra_pages > sb->s_bdi->io_pages)
 		ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages);
 	reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1);
_

      reply	other threads:[~2020-07-11 11:31 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10 16:14 WARNING in fat12_ent_blocknr syzbot
2020-07-11 11:28 ` OGAWA Hirofumi [this message]

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