On 07/10/2021 18:49, Dexuan Cui wrote:
After commit ea2f0f77538c, a 416-CPU VM running on Hyper-V hangs during boot because scsi_add_host_with_dma() sets shost->cmd_per_lun to a negative number (the below numbers may differ in different kernel versions): in drivers/scsi/storvsc_drv.c, storvsc_drv_init() sets 'max_outstanding_req_per_channel' to 352, and storvsc_probe() sets 'max_sub_channels' to (416 - 1) / 4 = 103 and sets scsi_driver.can_queue to 352 * (103 + 1) * (100 - 10) / 100 = 32947, which exceeds SHRT_MAX.
I think that you just need to mention that if can_queue exceeds SHRT_MAX, then there is a data truncation issue.
Use min_t(int, ...) to fix the issue.
Fixes: ea2f0f77538c ("scsi: core: Cap scsi_host cmd_per_lun at can_queue") Cc: stable@vger.kernel.org Signed-off-by: Dexuan Cui decui@microsoft.com
It looks ok, I'd just like to test it a bit more.
Thanks, John
v1 tried to fix the issue by changing the storvsc driver: https://lwn.net/ml/linux-kernel/BYAPR21MB1270BBC14D5F1AE69FC31A16BFB09@BYAPR...
v2 directly fixes the scsi core change instead as Michael Kelley and John Garry suggested (refer to the above link).
To be fair, it was Michael's suggestion
drivers/scsi/hosts.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c index 3f6f14f0cafb..24b72ee4246f 100644 --- a/drivers/scsi/hosts.c +++ b/drivers/scsi/hosts.c @@ -220,7 +220,8 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev, goto fail; }
- shost->cmd_per_lun = min_t(short, shost->cmd_per_lun,
- /* Use min_t(int, ...) in case shost->can_queue exceeds SHRT_MAX */
- shost->cmd_per_lun = min_t(int, shost->cmd_per_lun, shost->can_queue);
error = scsi_init_sense_cache(shost);