From 5b71fbdc64225b7a86944f4f0de80e59071187c7 Mon Sep 17 00:00:00 2001
From: Jan Beulich <JBeulich@suse.com>
Date: Fri, 2 Nov 2012 14:36:38 +0000
Subject: [PATCH] xen-pciback: simplify and tighten parsing of device IDs

Now that at least one of the conformance problems of the kernel's
sscanf() was addressed (commit da99075c1d368315e1508b6143226c0d27b621e0),
we can improve the parsing done in xen-pciback both in terms of code
readability and correctness (in particular properly rejecting input
strings not well formed).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/xen/xen-pciback/pci_stub.c | 83 ++++++++++++++----------------
 1 file changed, 39 insertions(+), 44 deletions(-)

diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index 961d664e2d2f..1a92739f4318 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -897,42 +897,35 @@ static struct pci_driver xen_pcibk_pci_driver = {
 static inline int str_to_slot(const char *buf, int *domain, int *bus,
 			      int *slot, int *func)
 {
-	int err;
-	char wc = '*';
+	int parsed = 0;
 
-	err = sscanf(buf, " %x:%x:%x.%x", domain, bus, slot, func);
-	switch (err) {
+	switch (sscanf(buf, " %x:%x:%x.%x %n", domain, bus, slot, func,
+		       &parsed)) {
 	case 3:
 		*func = -1;
-		err = sscanf(buf, " %x:%x:%x.%c", domain, bus, slot, &wc);
+		sscanf(buf, " %x:%x:%x.* %n", domain, bus, slot, &parsed);
 		break;
 	case 2:
 		*slot = *func = -1;
-		err = sscanf(buf, " %x:%x:*.%c", domain, bus, &wc);
-		if (err >= 2)
-			++err;
+		sscanf(buf, " %x:%x:*.* %n", domain, bus, &parsed);
 		break;
 	}
-	if (err == 4 && wc == '*')
+	if (parsed && !buf[parsed])
 		return 0;
-	else if (err < 0)
-		return -EINVAL;
 
 	/* try again without domain */
 	*domain = 0;
-	wc = '*';
-	err = sscanf(buf, " %x:%x.%x", bus, slot, func);
-	switch (err) {
+	switch (sscanf(buf, " %x:%x.%x %n", bus, slot, func, &parsed)) {
 	case 2:
 		*func = -1;
-		err = sscanf(buf, " %x:%x.%c", bus, slot, &wc);
+		sscanf(buf, " %x:%x.* %n", bus, slot, &parsed);
 		break;
 	case 1:
 		*slot = *func = -1;
-		err = sscanf(buf, " %x:*.%c", bus, &wc) + 1;
+		sscanf(buf, " %x:*.* %n", bus, &parsed);
 		break;
 	}
-	if (err == 3 && wc == '*')
+	if (parsed && !buf[parsed])
 		return 0;
 
 	return -EINVAL;
@@ -941,13 +934,20 @@ static inline int str_to_slot(const char *buf, int *domain, int *bus,
 static inline int str_to_quirk(const char *buf, int *domain, int *bus, int
 			       *slot, int *func, int *reg, int *size, int *mask)
 {
-	int err;
+	int parsed = 0;
+
+	sscanf(buf, " %4x:%2x:%2x.%d-%8x:%1x:%8x %n", domain, bus, slot, func,
+	       reg, size, mask, &parsed);
+	if (parsed && !buf[parsed])
+		return 0;
 
-	err =
-	    sscanf(buf, " %04x:%02x:%02x.%d-%08x:%1x:%08x", domain, bus, slot,
-		   func, reg, size, mask);
-	if (err == 7)
+	/* try again without domain */
+	*domain = 0;
+	sscanf(buf, " %2x:%2x.%d-%8x:%1x:%8x %n", bus, slot, func, reg, size,
+	       mask, &parsed);
+	if (parsed && !buf[parsed])
 		return 0;
+
 	return -EINVAL;
 }
 
@@ -1339,8 +1339,6 @@ static int __init pcistub_init(void)
 
 	if (pci_devs_to_hide && *pci_devs_to_hide) {
 		do {
-			char wc = '*';
-
 			parsed = 0;
 
 			err = sscanf(pci_devs_to_hide + pos,
@@ -1349,51 +1347,48 @@ static int __init pcistub_init(void)
 			switch (err) {
 			case 3:
 				func = -1;
-				err = sscanf(pci_devs_to_hide + pos,
-					     " (%x:%x:%x.%c) %n",
-					     &domain, &bus, &slot, &wc,
-					     &parsed);
+				sscanf(pci_devs_to_hide + pos,
+				       " (%x:%x:%x.*) %n",
+				       &domain, &bus, &slot, &parsed);
 				break;
 			case 2:
 				slot = func = -1;
-				err = sscanf(pci_devs_to_hide + pos,
-					     " (%x:%x:*.%c) %n",
-					     &domain, &bus, &wc, &parsed) + 1;
+				sscanf(pci_devs_to_hide + pos,
+				       " (%x:%x:*.*) %n",
+				       &domain, &bus, &parsed);
 				break;
 			}
 
-			if (err != 4 || wc != '*') {
+			if (!parsed) {
 				domain = 0;
-				wc = '*';
 				err = sscanf(pci_devs_to_hide + pos,
 					     " (%x:%x.%x) %n",
 					     &bus, &slot, &func, &parsed);
 				switch (err) {
 				case 2:
 					func = -1;
-					err = sscanf(pci_devs_to_hide + pos,
-						     " (%x:%x.%c) %n",
-						     &bus, &slot, &wc,
-						     &parsed);
+					sscanf(pci_devs_to_hide + pos,
+					       " (%x:%x.*) %n",
+					       &bus, &slot, &parsed);
 					break;
 				case 1:
 					slot = func = -1;
-					err = sscanf(pci_devs_to_hide + pos,
-						     " (%x:*.%c) %n",
-						     &bus, &wc, &parsed) + 1;
+					sscanf(pci_devs_to_hide + pos,
+					       " (%x:*.*) %n",
+					       &bus, &parsed);
 					break;
 				}
-				if (err != 3 || wc != '*')
-					goto parse_error;
 			}
 
+			if (parsed <= 0)
+				goto parse_error;
+
 			err = pcistub_device_id_add(domain, bus, slot, func);
 			if (err)
 				goto out;
 
-			/* if parsed<=0, we've reached the end of the string */
 			pos += parsed;
-		} while (parsed > 0 && pci_devs_to_hide[pos]);
+		} while (pci_devs_to_hide[pos]);
 	}
 
 	/* If we're the first PCI Device Driver to register, we're the
-- 
2.20.1