Re: [PATCH] zram: fix bug storing backing_dev

[Sergey Senozhatsky]

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@xxxxxxxxxx>
> Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
> 
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
> CC: LKML <linux-kernel@xxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>    [4.14+]

Thanks for Cc-ing Minchan.

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

> > -	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