linux-kernel - Re: BUG: KASAN: slab-out-of-bounds in ses_enclosure_data

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Message-ID: <1449256614.27077.11.camel@HansenPartnership.com>
Date:	Fri, 04 Dec 2015 11:16:54 -0800
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	emilne@...hat.com
Cc:	Andrea Gelmini <andrea.gelmini@...ma.net>,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	dgilbert@...erlog.com
Subject: Re: BUG: KASAN: slab-out-of-bounds in
 ses_enclosure_data_process+0x900/0xe50

On Fri, 2015-12-04 at 11:58 -0500, Ewan Milne wrote:
> On Thu, 2015-12-03 at 23:20 +0100, Andrea Gelmini wrote:
> > On Thu, Dec 03, 2015 at 12:59:06PM -0800, James Bottomley wrote:
> > > sg_map -i
> > > 
> > > in your system, you should see something with an inquiry string like
> > > enclosure.  It's the /dev/sg<n> of that you need to run sg_ses on.
> > 
> > root@...n:/home/gelma# sg_map -i
> > /dev/sg0  /dev/sda  ATA       Samsung SSD 850   1B6Q
> > /dev/sg1  /dev/sr0  HL-DT-ST  DVDRAM GU40N      QX23
> > /dev/sg2  /dev/sdb  WD        My Passport 0820  1007
> > /dev/sg3  WD        SES Device        1007
> > 
> > And following Douglas' instructions:
> > 
> > root@...n:/home/gelma# lsscsi -gs
> > [0:0:0:0]    disk    ATA      Samsung SSD 850  1B6Q  /dev/sda   /dev/sg0   1.02TB
> > [1:0:0:0]    cd/dvd  HL-DT-ST DVDRAM GU40N     QX23  /dev/sr0   /dev/sg1        -
> > [8:0:0:0]    disk    WD       My Passport 0820 1007  /dev/sdb   /dev/sg2   2.00TB
> > [8:0:0:1]    enclosu WD       SES Device       1007  -          /dev/sg3       
> > 
> > root@...n:/home/gelma# sg_ses /dev/sg3
> >   WD        SES Device        1007
> > Supported diagnostic pages:
> >   Supported Diagnostic Pages [sdp] [0x0]
> >   Short Enclosure Status (SES) [ses] [0x8]
> >   <unknown> [0x80]
> >   <unknown> [0x83]
> >   <unknown> [0x84]
> >   <unknown> [0x85]
> > 
> > 
> > Well, if it's better for you, I can give you root access to a machine with this device
> > connected to.
> > 
> > Thanks a lot for your time,
> > Andrea
> 
> There seems to be a problem with the ses code if the device only reports
> Short Enclosure Status.  We probably need to do something like:
> 
> diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c
> index eba183c..065a528 100644
> --- a/drivers/scsi/ses.c
> +++ b/drivers/scsi/ses.c
> @@ -537,6 +537,15 @@ static int ses_intf_add(struct device *cdev,
>         if (result)
>                 goto recv_failed;
>  
> +       /* If enclosure only supports Short Enclosure Status page (08),
> +        * it returns that page regardless of what we requested, and
> +        * only returns vendor-specific status.  There is nothing wrong
> +        * with such enclosures, we just can't make use of them. */
> +       if (hdr_buf[0] == 8) {
> +               err = -ENODEV;
> +               goto err_init_free_nomsg;
> +       }
> +
>         len = (hdr_buf[2] << 8) + hdr_buf[3] + 4;
>         buf = kzalloc(len, GFP_KERNEL);
>         if (!buf)
> @@ -646,9 +655,10 @@ static int ses_intf_add(struct device *cdev,
>         kfree(ses_dev->page2);
>         kfree(ses_dev->page1);
>   err_init_free:
> +       sdev_printk(KERN_ERR, sdev, "Failed to bind enclosure %d\n",
> err);
> + err_init_free_nomsg:
>         kfree(ses_dev);
>         kfree(hdr_buf);
> -       sdev_printk(KERN_ERR, sdev, "Failed to bind enclosure %d\n",
> err);
>         return err;
>  }
> 
> Otherwise we go off issuing commands for pages the device says it won't
> return.  I don't see offhand how this would cause KASAN errors though.

I think we have two separate bugs.  One is the usual USB devices getting
into a new SCSI standard and getting it wrong.  The other looks to be an
enumeration problem ... possibly because ses2 added an indexed
descriptor which current SES doesn't cope with.

Anyway, in concentrating on the USB problem first, I think we need to
code a little more defensively, like this.

James

---

diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c
index dcb0d76..7d9cec5 100644
--- a/drivers/scsi/ses.c
+++ b/drivers/scsi/ses.c
@@ -84,6 +84,7 @@ static void init_device_slot_control(unsigned char *dest_desc,
 static int ses_recv_diag(struct scsi_device *sdev, int page_code,
 			 void *buf, int bufflen)
 {
+	int ret;
 	unsigned char cmd[] = {
 		RECEIVE_DIAGNOSTIC,
 		1,		/* Set PCV bit */
@@ -92,9 +93,26 @@ static int ses_recv_diag(struct scsi_device *sdev, int page_code,
 		bufflen & 0xff,
 		0
 	};
+	unsigned char recv_page_code;
 
-	return scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buf, bufflen,
+	ret =  scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buf, bufflen,
 				NULL, SES_TIMEOUT, SES_RETRIES, NULL);
+	if (unlikely(!ret))
+		return ret;
+
+	recv_page_code = ((unsigned char *)buf)[0];
+
+	if (likely(recv_page_code == page_code))
+		return ret;
+
+	/* successful diagnostic but wrong page code.  This happens to some
+	 * USB devices, just print a message and pretend there was an error */
+
+	sdev_printk(KERN_ERR, sdev,
+		    "Wrong diagnostic page; asked for %d got %u\n",
+		    page_code, recv_page_code);
+
+	return -EINVAL;
 }
 
 static int ses_send_diag(struct scsi_device *sdev, int page_code,


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