Patch "libata: array underflow in ata_find_dev()" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

libata: array underflow in ata_find_dev()

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
libata-array-underflow-in-ata_find_dev.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dan Carpenter <[email protected]>
Date: Wed, 19 Jul 2017 13:06:41 +0300
Subject: libata: array underflow in ata_find_dev()

From: Dan Carpenter <[email protected]>

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()

---
 drivers/ata/libata-scsi.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -2798,10 +2798,12 @@ static unsigned int atapi_xlat(struct at
 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];
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/libata-array-underflow-in-ata_find_dev.patch