zram: rework copy of compressor name in comp_algorithm_store()

comp_algorithm_store() passes the size of the source buffer to strlcpy()
instead of the destination buffer size.  Make it explicit that the two
buffers have the same size and use strcpy() instead of strlcpy().  The
latter can be done safely since the function ensures that the string in
the source buffer is terminated.

Link: http://lkml.kernel.org/r/20170803163350.45245-1-mka@chromium.org
Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/zram/zram_drv.c

@@ -308,7 +308,7 @@ static ssize_t comp_algorithm_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t len)
 {
 	struct zram *zram = dev_to_zram(dev);
-	char compressor[CRYPTO_MAX_ALG_NAME];
+	char compressor[ARRAY_SIZE(zram->compressor)];
 	size_t sz;
 
 	strlcpy(compressor, buf, sizeof(compressor));
@@ -327,7 +327,7 @@ static ssize_t comp_algorithm_store(struct device *dev,
 		return -EBUSY;
 	}
 
-	strlcpy(zram->compressor, compressor, sizeof(compressor));
+	strcpy(zram->compressor, compressor);
 	up_write(&zram->init_lock);
 	return len;
 }