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

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Date:   Tue, 9 Jun 2020 09:37:48 +0900
From:   "Namjae Jeon" <namjae.jeon@...sung.com>
To:     "'Dan Carpenter'" <dan.carpenter@...cle.com>
Cc:     "'Sungjong Seo'" <sj1557.seo@...sung.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kernel-janitors@...r.kernel.org>,
        "'Tetsuhiro Kohada'" <kohada.t2@...il.com>
Subject: RE: [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>
Applied. Thanks!
> ---
>  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