From 9393c8de628cf0968d81a17cc11841e42191e041 Mon Sep 17 00:00:00 2001 From: Michael Schmitz Date: Tue, 5 Nov 2019 15:49:10 +1300 Subject: [PATCH] scsi: core: Handle drivers which set sg_tablesize to zero 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 Link: https://lore.kernel.org/r/1572922150-4358-1-git-send-email-schmitzmic@gmail.com Signed-off-by: Michael Schmitz Signed-off-by: Martin K. Petersen --- drivers/scsi/scsi_lib.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index dc210b9d4896..3a352a4601b1 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1882,7 +1882,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) { unsigned int cmd_size, sgl_size; - sgl_size = scsi_mq_inline_sgl_size(shost); + sgl_size = max_t(unsigned int, sizeof(struct scatterlist), + scsi_mq_inline_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) +