USB: uhci: check buffer length to avoid memory overflow

  for function uhci_sprint_schedule:
    the buffer len is MAX_OUTPUT: 64 * 1024, which may not be enough:
      may loop UHCI_NUMFRAMES times (UHCI_NUMFRAMES is 1024)
      each time of loop may get more than 64 bytes
    so need check the buffer length to avoid memory overflow

  this patch fix it like this:
    at first, make enough room for buffering the exceeding contents
    judge the contents which written whether bigger than buffer length
    if bigger (the exceeding contents will be in the exceeding buffer)
      break current work flow, and return.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/uhci-debug.c

@@ -16,6 +16,8 @@
 
 #include "uhci-hcd.h"
 
+#define EXTRA_SPACE	1024
+
 static struct dentry *uhci_debugfs_root;
 
 #ifdef DEBUG
@@ -44,10 +46,6 @@ static int uhci_show_td(struct uhci_hcd *uhci, struct uhci_td *td, char *buf,
 	char *spid;
 	u32 status, token;
 
-	/* Try to make sure there's enough memory */
-	if (len < 160)
-		return 0;
-
 	status = td_status(uhci, td);
 	out += sprintf(out, "%*s[%p] link (%08x) ", space, "", td,
 		hc32_to_cpu(uhci, td->link));
@@ -64,6 +62,8 @@ static int uhci_show_td(struct uhci_hcd *uhci, struct uhci_td *td, char *buf,
 		(status & TD_CTRL_CRCTIMEO) ? "CRC/Timeo " : "",
 		(status & TD_CTRL_BITSTUFF) ? "BitStuff " : "",
 		status & 0x7ff);
+	if (out - buf > len)
+		goto done;
 
 	token = td_token(uhci, td);
 	switch (uhci_packetid(token)) {
@@ -90,6 +90,9 @@ static int uhci_show_td(struct uhci_hcd *uhci, struct uhci_td *td, char *buf,
 		spid);
 	out += sprintf(out, "(buf=%08x)\n", hc32_to_cpu(uhci, td->buffer));
 
+done:
+	if (out - buf > len)
+		out += sprintf(out, " ...\n");
 	return out - buf;
 }
 
@@ -101,8 +104,6 @@ static int uhci_show_urbp(struct uhci_hcd *uhci, struct urb_priv *urbp,
 	int i, nactive, ninactive;
 	char *ptype;
 
-	if (len < 200)
-		return 0;
 
 	out += sprintf(out, "urb_priv [%p] ", urbp);
 	out += sprintf(out, "urb [%p] ", urbp->urb);
@@ -110,6 +111,8 @@ static int uhci_show_urbp(struct uhci_hcd *uhci, struct urb_priv *urbp,
 	out += sprintf(out, "Dev=%d ", usb_pipedevice(urbp->urb->pipe));
 	out += sprintf(out, "EP=%x(%s) ", usb_pipeendpoint(urbp->urb->pipe),
 			(usb_pipein(urbp->urb->pipe) ? "IN" : "OUT"));
+	if (out - buf > len)
+		goto done;
 
 	switch (usb_pipetype(urbp->urb->pipe)) {
 	case PIPE_ISOCHRONOUS: ptype = "ISO"; break;
@@ -128,6 +131,9 @@ static int uhci_show_urbp(struct uhci_hcd *uhci, struct urb_priv *urbp,
 		out += sprintf(out, " Unlinked=%d", urbp->urb->unlinked);
 	out += sprintf(out, "\n");
 
+	if (out - buf > len)
+		goto done;
+
 	i = nactive = ninactive = 0;
 	list_for_each_entry(td, &urbp->td_list, list) {
 		if (urbp->qh->type != USB_ENDPOINT_XFER_ISOC &&
@@ -135,6 +141,8 @@ static int uhci_show_urbp(struct uhci_hcd *uhci, struct urb_priv *urbp,
 			out += sprintf(out, "%*s%d: ", space + 2, "", i);
 			out += uhci_show_td(uhci, td, out,
 					len - (out - buf), 0);
+			if (out - buf > len)
+				goto tail;
 		} else {
 			if (td_status(uhci, td) & TD_CTRL_ACTIVE)
 				++nactive;
@@ -146,7 +154,10 @@ static int uhci_show_urbp(struct uhci_hcd *uhci, struct urb_priv *urbp,
 		out += sprintf(out, "%*s[skipped %d inactive and %d active "
 				"TDs]\n",
 				space, "", ninactive, nactive);
-
+done:
+	if (out - buf > len)
+		out += sprintf(out, " ...\n");
+tail:
 	return out - buf;
 }
 
@@ -158,10 +169,6 @@ static int uhci_show_qh(struct uhci_hcd *uhci,
 	__hc32 element = qh_element(qh);
 	char *qtype;
 
-	/* Try to make sure there's enough memory */
-	if (len < 80 * 7)
-		return 0;
-
 	switch (qh->type) {
 	case USB_ENDPOINT_XFER_ISOC: qtype = "ISO"; break;
 	case USB_ENDPOINT_XFER_INT: qtype = "INT"; break;
@@ -182,6 +189,8 @@ static int uhci_show_qh(struct uhci_hcd *uhci,
 	else if (qh->type == USB_ENDPOINT_XFER_INT)
 		out += sprintf(out, "%*s    period %d phase %d load %d us\n",
 				space, "", qh->period, qh->phase, qh->load);
+	if (out - buf > len)
+		goto done;
 
 	if (element & UHCI_PTR_QH(uhci))
 		out += sprintf(out, "%*s  Element points to QH (bug?)\n", space, "");
@@ -195,11 +204,17 @@ static int uhci_show_qh(struct uhci_hcd *uhci,
 	if (!(element & ~(UHCI_PTR_QH(uhci) | UHCI_PTR_DEPTH(uhci))))
 		out += sprintf(out, "%*s  Element is NULL (bug?)\n", space, "");
 
+	if (out - buf > len)
+		goto done;
+
 	if (list_empty(&qh->queue)) {
 		out += sprintf(out, "%*s  queue is empty\n", space, "");
-		if (qh == uhci->skel_async_qh)
+		if (qh == uhci->skel_async_qh) {
 			out += uhci_show_td(uhci, uhci->term_td, out,
 					len - (out - buf), 0);
+			if (out - buf > len)
+				goto tail;
+		}
 	} else {
 		struct urb_priv *urbp = list_entry(qh->queue.next,
 				struct urb_priv, node);
@@ -211,9 +226,12 @@ static int uhci_show_qh(struct uhci_hcd *uhci,
 					space, "");
 		i = nurbs = 0;
 		list_for_each_entry(urbp, &qh->queue, node) {
-			if (++i <= 10)
+			if (++i <= 10) {
 				out += uhci_show_urbp(uhci, urbp, out,
 						len - (out - buf), space + 2);
+				if (out - buf > len)
+					goto tail;
+			}
 			else
 				++nurbs;
 		}
@@ -222,24 +240,27 @@ static int uhci_show_qh(struct uhci_hcd *uhci,
 					space, "", nurbs);
 	}
 
+	if (out - buf > len)
+		goto done;
+
 	if (qh->dummy_td) {
 		out += sprintf(out, "%*s  Dummy TD\n", space, "");
 		out += uhci_show_td(uhci, qh->dummy_td, out,
 				len - (out - buf), 0);
+		if (out - buf > len)
+			goto tail;
 	}
 
+done:
+	if (out - buf > len)
+		out += sprintf(out, " ...\n");
+tail:
 	return out - buf;
 }
 
-static int uhci_show_sc(int port, unsigned short status, char *buf, int len)
+static int uhci_show_sc(int port, unsigned short status, char *buf)
 {
-	char *out = buf;
-
-	/* Try to make sure there's enough memory */
-	if (len < 160)
-		return 0;
-
-	out += sprintf(out, "  stat%d     =     %04x  %s%s%s%s%s%s%s%s%s%s\n",
+	return sprintf(buf, "  stat%d     =     %04x  %s%s%s%s%s%s%s%s%s%s\n",
 		port,
 		status,
 		(status & USBPORTSC_SUSP) ?	" Suspend" : "",
@@ -252,19 +273,12 @@ static int uhci_show_sc(int port, unsigned short status, char *buf, int len)
 		(status & USBPORTSC_PE) ?	" Enabled" : "",
 		(status & USBPORTSC_CSC) ?	" ConnectChange" : "",
 		(status & USBPORTSC_CCS) ?	" Connected" : "");
-
-	return out - buf;
 }
 
-static int uhci_show_root_hub_state(struct uhci_hcd *uhci, char *buf, int len)
+static int uhci_show_root_hub_state(struct uhci_hcd *uhci, char *buf)
 {
-	char *out = buf;
 	char *rh_state;
 
-	/* Try to make sure there's enough memory */
-	if (len < 60)
-		return 0;
-
 	switch (uhci->rh_state) {
 	    case UHCI_RH_RESET:
 		rh_state = "reset";		break;
@@ -283,9 +297,8 @@ static int uhci_show_root_hub_state(struct uhci_hcd *uhci, char *buf, int len)
 	    default:
 		rh_state = "?";			break;
 	}
-	out += sprintf(out, "Root-hub state: %s   FSBR: %d\n",
+	return sprintf(buf, "Root-hub state: %s   FSBR: %d\n",
 			rh_state, uhci->fsbr_is_on);
-	return out - buf;
 }
 
 static int uhci_show_status(struct uhci_hcd *uhci, char *buf, int len)
@@ -296,9 +309,6 @@ static int uhci_show_status(struct uhci_hcd *uhci, char *buf, int len)
 	unsigned char sof;
 	unsigned short portsc1, portsc2;
 
-	/* Try to make sure there's enough memory */
-	if (len < 80 * 9)
-		return 0;
 
 	usbcmd    = uhci_readw(uhci, 0);
 	usbstat   = uhci_readw(uhci, 2);
@@ -319,6 +329,8 @@ static int uhci_show_status(struct uhci_hcd *uhci, char *buf, int len)
 		(usbcmd & USBCMD_GRESET) ?  "GRESET " : "",
 		(usbcmd & USBCMD_HCRESET) ? "HCRESET " : "",
 		(usbcmd & USBCMD_RS) ?      "RS " : "");
+	if (out - buf > len)
+		goto done;
 
 	out += sprintf(out, "  usbstat   =     %04x   %s%s%s%s%s%s\n",
 		usbstat,
@@ -328,19 +340,33 @@ static int uhci_show_status(struct uhci_hcd *uhci, char *buf, int len)
 		(usbstat & USBSTS_RD) ?     "ResumeDetect " : "",
 		(usbstat & USBSTS_ERROR) ?  "USBError " : "",
 		(usbstat & USBSTS_USBINT) ? "USBINT " : "");
+	if (out - buf > len)
+		goto done;
 
 	out += sprintf(out, "  usbint    =     %04x\n", usbint);
 	out += sprintf(out, "  usbfrnum  =   (%d)%03x\n", (usbfrnum >> 10) & 1,
 		0xfff & (4*(unsigned int)usbfrnum));
 	out += sprintf(out, "  flbaseadd = %08x\n", flbaseadd);
 	out += sprintf(out, "  sof       =       %02x\n", sof);
-	out += uhci_show_sc(1, portsc1, out, len - (out - buf));
-	out += uhci_show_sc(2, portsc2, out, len - (out - buf));
-	out += sprintf(out, "Most recent frame: %x (%d)   "
-			"Last ISO frame: %x (%d)\n",
+	if (out - buf > len)
+		goto done;
+
+	out += uhci_show_sc(1, portsc1, out);
+	if (out - buf > len)
+		goto done;
+
+	out += uhci_show_sc(2, portsc2, out);
+	if (out - buf > len)
+		goto done;
+
+	out += sprintf(out,
+			"Most recent frame: %x (%d)   Last ISO frame: %x (%d)\n",
 			uhci->frame_number, uhci->frame_number & 1023,
 			uhci->last_iso_frame, uhci->last_iso_frame & 1023);
 
+done:
+	if (out - buf > len)
+		out += sprintf(out, " ...\n");
 	return out - buf;
 }
 
@@ -360,9 +386,13 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 		"int8", "int4", "int2", "async", "term"
 	};
 
-	out += uhci_show_root_hub_state(uhci, out, len - (out - buf));
+	out += uhci_show_root_hub_state(uhci, out);
+	if (out - buf > len)
+		goto done;
 	out += sprintf(out, "HC status\n");
 	out += uhci_show_status(uhci, out, len - (out - buf));
+	if (out - buf > len)
+		goto tail;
 
 	out += sprintf(out, "Periodic load table\n");
 	for (i = 0; i < MAX_PHASE; ++i) {
@@ -375,7 +405,7 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 			uhci_to_hcd(uhci)->self.bandwidth_int_reqs,
 			uhci_to_hcd(uhci)->self.bandwidth_isoc_reqs);
 	if (debug <= 1)
-		return out - buf;
+		goto tail;
 
 	out += sprintf(out, "Frame List\n");
 	nframes = 10;
@@ -383,6 +413,8 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 	for (i = 0; i < UHCI_NUMFRAMES; ++i) {
 		__hc32 qh_dma;
 
+		if (out - buf > len)
+			goto done;
 		j = 0;
 		td = uhci->frame_cpu[i];
 		link = uhci->frame[i];
@@ -401,15 +433,20 @@ static int uhci_sprint_schedule(struct uhci_hcd *uhci, char *buf, int len)
 			td = list_entry(tmp, struct uhci_td, fl_list);
 			tmp = tmp->next;
 			if (link != LINK_TO_TD(uhci, td)) {
-				if (nframes > 0)
+				if (nframes > 0) {
 					out += sprintf(out, "    link does "
 						"not match list entry!\n");
-				else
+					if (out - buf > len)
+						goto done;
+				} else
 					++nerrs;
 			}
-			if (nframes > 0)
+			if (nframes > 0) {
 				out += uhci_show_td(uhci, td, out,
 						len - (out - buf), 4);
+				if (out - buf > len)
+					goto tail;
+			}
 			link = td->link;
 		} while (tmp != head);
 
@@ -426,6 +463,8 @@ check_link:
 				out += sprintf(out, "   link does not match "
 					"QH (%08x)!\n",
 					hc32_to_cpu(uhci, qh_dma));
+				if (out - buf > len)
+					goto done;
 			} else
 				++nerrs;
 		}
@@ -436,6 +475,9 @@ check_link:
 
 	out += sprintf(out, "Skeleton QHs\n");
 
+	if (out - buf > len)
+		goto done;
+
 	fsbr_link = 0;
 	for (i = 0; i < UHCI_NUM_SKELQH; ++i) {
 		int cnt = 0;
@@ -443,11 +485,16 @@ check_link:
 		qh = uhci->skelqh[i];
 		out += sprintf(out, "- skel_%s_qh\n", qh_names[i]); \
 		out += uhci_show_qh(uhci, qh, out, len - (out - buf), 4);
+		if (out - buf > len)
+			goto tail;
 
 		/* Last QH is the Terminating QH, it's different */
 		if (i == SKEL_TERM) {
-			if (qh_element(qh) != LINK_TO_TD(uhci, uhci->term_td))
+			if (qh_element(qh) != LINK_TO_TD(uhci, uhci->term_td)) {
 				out += sprintf(out, "    skel_term_qh element is not set to term_td!\n");
+				if (out - buf > len)
+					goto done;
+			}
 			link = fsbr_link;
 			if (!link)
 				link = LINK_TO_QH(uhci, uhci->skel_term_qh);
@@ -460,9 +507,12 @@ check_link:
 		while (tmp != head) {
 			qh = list_entry(tmp, struct uhci_qh, node);
 			tmp = tmp->next;
-			if (++cnt <= 10)
+			if (++cnt <= 10) {
 				out += uhci_show_qh(uhci, qh, out,
 						len - (out - buf), 4);
+				if (out - buf > len)
+					goto tail;
+			}
 			if (!fsbr_link && qh->skel >= SKEL_FSBR)
 				fsbr_link = LINK_TO_QH(uhci, qh);
 		}
@@ -481,8 +531,15 @@ check_link:
 check_qh_link:
 		if (qh->link != link)
 			out += sprintf(out, "    last QH not linked to next skeleton!\n");
+
+		if (out - buf > len)
+			goto done;
 	}
 
+done:
+	if (out - buf > len)
+		out += sprintf(out, " ...\n");
+tail:
 	return out - buf;
 }
 
@@ -514,7 +571,8 @@ static int uhci_debug_open(struct inode *inode, struct file *file)
 	up->size = 0;
 	spin_lock_irqsave(&uhci->lock, flags);
 	if (uhci->is_initialized)
-		up->size = uhci_sprint_schedule(uhci, up->data, MAX_OUTPUT);
+		up->size = uhci_sprint_schedule(uhci, up->data,
+					MAX_OUTPUT - EXTRA_SPACE);
 	spin_unlock_irqrestore(&uhci->lock, flags);
 
 	file->private_data = up;

drivers/usb/host/uhci-hcd.c

@@ -462,8 +462,8 @@ static irqreturn_t uhci_irq(struct usb_hcd *hcd)
 					"very bad!\n");
 				if (debug > 1 && errbuf) {
 					/* Print the schedule for debugging */
-					uhci_sprint_schedule(uhci,
-							errbuf, ERRBUF_LEN);
+					uhci_sprint_schedule(uhci, errbuf,
+						ERRBUF_LEN - EXTRA_SPACE);
 					lprintk(errbuf);
 				}
 				uhci_hc_died(uhci);

drivers/usb/host/uhci-q.c

@@ -1200,7 +1200,7 @@ static int uhci_result_common(struct uhci_hcd *uhci, struct urb *urb)
 				if (debug > 1 && errbuf) {
 					/* Print the chain for debugging */
 					uhci_show_qh(uhci, urbp->qh, errbuf,
-							ERRBUF_LEN, 0);
+						ERRBUF_LEN - EXTRA_SPACE, 0);
 					lprintk(errbuf);
 				}
 			}