From: Michael Schmitz schmitzmic@gmail.com
commit 9393c8de628cf0968d81a17cc11841e42191e041 upstream.
In scsi_mq_setup_tags(), cmd_size is calculated based on zero size for the scatter-gather list in case the low level driver uses SG_NONE in its host template.
cmd_size is passed on to the block layer for calculation of the request size, and we've seen NULL pointer dereference errors from the block layer in drivers where SG_NONE is used and a mq IO scheduler is active, apparently as a consequence of this (see commit 68ab2d76e4be ("scsi: cxlflash: Set sg_tablesize to 1 instead of SG_NONE"), and a recent patch by Finn Thain converting the three m68k NFR5380 drivers to avoid setting SG_NONE).
Try to avoid these errors by accounting for at least one sg list entry when calculating cmd_size, regardless of whether the low level driver set a zero sg_tablesize.
Tested on 030 m68k with the atari_scsi driver - setting sg_tablesize to SG_NONE no longer results in a crash when loading this driver.
CC: Finn Thain fthain@telegraphics.com.au Link: https://lore.kernel.org/r/1572922150-4358-1-git-send-email-schmitzmic@gmail.... Signed-off-by: Michael Schmitz schmitzmic@gmail.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/scsi/scsi_lib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2371,7 +2371,8 @@ int scsi_mq_setup_tags(struct Scsi_Host { unsigned int cmd_size, sgl_size;
- sgl_size = scsi_mq_sgl_size(shost); + sgl_size = max_t(unsigned int, sizeof(struct scatterlist), + scsi_mq_sgl_size(shost)); cmd_size = sizeof(struct scsi_cmnd) + shost->hostt->cmd_size + sgl_size; if (scsi_host_get_prot(shost)) cmd_size += sizeof(struct scsi_data_buffer) + sgl_size;