linux-kernel - Re: [PATCH] zram: fix bug storing backing

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Message-ID: <20180813073825.GA1062@jagdpanzerIV>
Date:   Mon, 13 Aug 2018 16:38:25 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Peter Kalauskas <peskal@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] zram: fix bug storing backing_dev

On (08/13/18 15:16), Minchan Kim wrote:
> > The call to strlcpy in backing_dev_store is incorrect. It should take
> > the size of the destination buffer instead of the size of the source
> > buffer.  Additionally, ignore the newline character (\n) when reading
> > the new file_name buffer. This makes it possible to set the backing_dev
> > as follows:
> > 
> >   echo /dev/sdX > /sys/block/zram0/backing_dev
> > 
> > Signed-off-by: Peter Kalauskas <peskal@...gle.com>
> Acked-by: Minchan Kim <minchan@...nel.org>
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
> CC: LKML <linux-kernel@...r.kernel.org>
> Cc: <stable@...r.kernel.org>    [4.14+]

Thanks for Cc-ing Minchan.

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

> > -	strlcpy(file_name, buf, len);

This is quite interesting. The reason it worked before was the fact that
strlcpy() copies 'len - 1' bytes, which is strlen(buf) - 1 in our case,
so it accidentally didn't copy the trailing new line symbol. Which also
means that "echo -n /dev/sdX" most likely was broken.

	-ss