Re: [PATCH] commands: md: don't leak heap memory with unaligned accesses

From: Sascha Hauer <sha@pengutronix.de>
To: Ahmad Fatoum <ahmad@a3f.at>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] commands: md: don't leak heap memory with unaligned accesses
Date: Mon, 21 Jun 2021 09:58:09 +0200	[thread overview]
Message-ID: <20210621075809.GP9782@pengutronix.de> (raw)
In-Reply-To: <20210619054217.499815-1-ahmad@a3f.at>

On Sat, Jun 19, 2021 at 07:42:17AM +0200, Ahmad Fatoum wrote:
> Doing unaligned near file end returns bogus results:
> 
> 	barebox@Sandbox:/ md -s /dev/stickypage 4095
> 	00000fff: 959ff8ff                                           .
> 
> That 0x959ff8 is heap memory next to the buffer md had allocated.
> Fix this by adding some zeroed padding after the buffer, so it instead
> reads:
> 
> 	00000fff: 000000ff                                           .
> 
> This is arguably better user experience.
> This only applies to non-mappable fd's. For e.g. /dev/mem, unaligned
> accesses will still be passed as-is.
> 
> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at>
> ---
>  commands/md.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks

Sascha

> 
> diff --git a/commands/md.c b/commands/md.c
> index ef6a1e1bc0b1..d80c7cca0ce4 100644
> --- a/commands/md.c
> +++ b/commands/md.c
> @@ -59,7 +59,7 @@ static int do_mem_md(int argc, char *argv[])
>  		goto out;
>  	}
>  
> -	buf = xmalloc(RW_BUF_SIZE);
> +	buf = xzalloc(RW_BUF_SIZE + 7);
>  
>  	do {
>  		now = min(size, (loff_t)RW_BUF_SIZE);
> -- 
> 2.32.0.rc0
> 
> 
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