commit 9393c8de628c 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.d, and an empty message aborts the commit.
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 for the
cxflash driver, 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 caculating 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.
Backport of commit 9393c8de628c to stable kernels before 4.19 which lack
commit 3dccdf53c2f3 ("scsi: core: avoid preallocating big SGL for data"),
as requestef by Sasha Levin.
Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Cc: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Cc: Sasha Levin <sashal@xxxxxxxxxx>
Cc: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
drivers/scsi/scsi_lib.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 0adfb3b..e0a4ad9 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2356,7 +2356,8 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost)
{
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;
--
1.7.0.4
