Commit cecbc9ce authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

null_blk: Zero-initialize read buffers in non-memory-backed mode 



This patch suppresses an uninteresting KMSAN complaint without affecting
performance of the null_blk driver if CONFIG_KMSAN is disabled.

Reported-by: default avatarAlexander Potapenko <glider@google.com>
Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Tested-by: default avatarAlexander Potapenko <glider@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 854b5f01

drivers/block/null_blk_main.c

+26 −0
Original line number Diff line number Diff line
@@ -1250,8 +1250,34 @@ static inline blk_status_t null_handle_memory_backed(struct nullb_cmd *cmd, 
	return errno_to_blk_status(err);

}



static void nullb_zero_read_cmd_buffer(struct nullb_cmd *cmd)

{

	struct nullb_device *dev = cmd->nq->dev;

	struct bio *bio;



	if (dev->memory_backed)

		return;



	if (dev->queue_mode == NULL_Q_BIO && bio_op(cmd->bio) == REQ_OP_READ) {

		zero_fill_bio(cmd->bio);

	} else if (req_op(cmd->rq) == REQ_OP_READ) {

		__rq_for_each_bio(bio, cmd->rq)

			zero_fill_bio(bio);

	}

}



static inline void nullb_complete_cmd(struct nullb_cmd *cmd)

{

	/*

	 * Since root privileges are required to configure the null_blk

	 * driver, it is fine that this driver does not initialize the

	 * data buffers of read commands. Zero-initialize these buffers

	 * anyway if KMSAN is enabled to prevent that KMSAN complains

	 * about null_blk not initializing read data buffers.

	 */

	if (IS_ENABLED(CONFIG_KMSAN))

		nullb_zero_read_cmd_buffer(cmd);



	/* Complete IO by inline, softirq or timer */

	switch (cmd->nq->dev->irqmode) {

	case NULL_IRQ_SOFTIRQ: