From: Dan Carpenter Date: Wed, 19 Jul 2017 10:06:41 +0000 (+0300) Subject: libata: array underflow in ata_find_dev() X-Git-Tag: v4.9.42~91 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=804b1a9f0aeabc002b162c5b1861d65e1316a53a;p=platform%2Fkernel%2Flinux-amlogic.git libata: array underflow in ata_find_dev() commit 59a5e266c3f5c1567508888dd61a45b86daed0fa upstream. My static checker complains that "devno" can be negative, meaning that we read before the start of the loop. I've looked at the code, and I think the warning is right. This come from /proc so it's root only or it would be quite a quite a serious bug. The call tree looks like this: proc_scsi_write() <- gets id and channel from simple_strtoul() -> scsi_add_single_device() <- calls shost->transportt->user_scan() -> ata_scsi_user_scan() -> ata_find_dev() Signed-off-by: Dan Carpenter Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 8e575fbdf31d..e3e10e8f6f6a 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -2971,10 +2971,12 @@ static unsigned int atapi_xlat(struct ata_queued_cmd *qc) static struct ata_device *ata_find_dev(struct ata_port *ap, int devno) { if (!sata_pmp_attached(ap)) { - if (likely(devno < ata_link_max_devices(&ap->link))) + if (likely(devno >= 0 && + devno < ata_link_max_devices(&ap->link))) return &ap->link.device[devno]; } else { - if (likely(devno < ap->nr_pmp_links)) + if (likely(devno >= 0 && + devno < ap->nr_pmp_links)) return &ap->pmp_link[devno].device[0]; }