linux-kernel - Re: [PATCH v2] mtd: rawnand: Fix a memory leak bug

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Message-ID: <20190826150553.3f758c84@collabora.com>
Date:   Mon, 26 Aug 2019 15:05:53 +0200
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     Wenwen Wang <wenwen@...uga.edu>
Cc:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-mtd@...ts.infradead.org (open list:NAND FLASH SUBSYSTEM),
        linux-kernel@...r.kernel.org (open list)
Subject: Re: [PATCH v2] mtd: rawnand: Fix a memory leak bug

On Sun, 18 Aug 2019 21:46:04 -0500
Wenwen Wang <wenwen@...uga.edu> wrote:

> In nand_scan_bbt(), a temporary buffer 'buf' is allocated through
> vmalloc(). However, if check_create() fails, 'buf' is not deallocated,
> leading to a memory leak bug. To fix this issue, free 'buf' before
> returning the error.
> 
> Signed-off-by: Wenwen Wang <wenwen@...uga.edu>
> ---
>  drivers/mtd/nand/raw/nand_bbt.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
> index 2ef15ef..96045d6 100644
> --- a/drivers/mtd/nand/raw/nand_bbt.c
> +++ b/drivers/mtd/nand/raw/nand_bbt.c
> @@ -1232,7 +1232,7 @@ static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
>  	if (!td) {
>  		if ((res = nand_memory_bbt(this, bd))) {
>  			pr_err("nand_bbt: can't scan flash and build the RAM-based BBT\n");
> -			goto err;
> +			goto err_free_bbt;
>  		}
>  		return 0;
>  	}
> @@ -1245,7 +1245,7 @@ static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
>  	buf = vmalloc(len);
>  	if (!buf) {
>  		res = -ENOMEM;
> -		goto err;
> +		goto err_free_bbt;
>  	}
>  
>  	/* Is the bbt at a given page? */
> @@ -1258,7 +1258,7 @@ static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
>  
>  	res = check_create(this, buf, bd);

I know it's too late, but calling

	vfree(buf);

here

>  	if (res)
> -		goto err;
> +		goto err_free_buf;
>  
>  	/* Prevent the bbt regions from erasing / writing */
>  	mark_bbt_region(this, td);
> @@ -1268,7 +1268,9 @@ static int nand_scan_bbt(struct nand_chip *this, struct nand_bbt_descr *bd)
>  	vfree(buf);

instead of here would have fixed the leak without the need for an extra
err label.

>  	return 0;
>  
> -err:
> +err_free_buf:
> +	vfree(buf);
> +err_free_bbt:
>  	kfree(this->bbt);
>  	this->bbt = NULL;
>  	return res;