linux-kernel - [PATCH] exfat: Fix pontential use after free in exfat_load_upcase

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Message-ID: <20200608141629.GA1912173@mwanda>
Date:   Mon, 8 Jun 2020 17:16:29 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Namjae Jeon <namjae.jeon@...sung.com>,
        Tetsuhiro Kohada <kohada.t2@...il.com>
Cc:     Sungjong Seo <sj1557.seo@...sung.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] exfat: Fix pontential use after free in
 exfat_load_upcase_table()

This code calls brelse(bh) and then dereferences "bh" on the next line
resulting in a possible use after free.  The brelse() should just be
moved down a line.

Fixes: b676fdbcf4c8 ("exfat: standardize checksum calculation")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 fs/exfat/nls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c
index c1ec056954974..57b5a7a4d1f7a 100644
--- a/fs/exfat/nls.c
+++ b/fs/exfat/nls.c
@@ -692,8 +692,8 @@ static int exfat_load_upcase_table(struct super_block *sb,
 				index++;
 			}
 		}
-		brelse(bh);
 		chksum = exfat_calc_chksum32(bh->b_data, i, chksum, CS_DEFAULT);
+		brelse(bh);
 	}
 
 	if (index >= 0xFFFF && utbl_checksum == chksum)
-- 
2.26.2