From: Dan Carpenter Date: Wed, 19 Jul 2017 10:06:41 +0000 (+0300) Subject: libata: array underflow in ata_find_dev() X-Git-Tag: v3.2.95~139 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2679d58535a3b67664655760611920c32fe5279f;p=thirdparty%2Fkernel%2Fstable.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: Ben Hutchings --- diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 01a019eaf30a5..c6f7fa440f120 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -2755,10 +2755,12 @@ 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]; }