Merge branch 'debug-net'

Eric Dumazet says:

====================
net: CONFIG_DEBUG_NET and friends

This patch series is inspired by some syzbot reports
hinting that skb transport_header might be not set
in places we expect it being set.

Add a new CONFIG_DEBUG_NET option
and DEBUG_NET_WARN_ON_ONCE() helper, so that we can start
adding more sanity checks in the future.

Replace two BUG() in skb_checksum_help()
with less risky code.

v2: make first patch compile on more arches/compilers
    add the 5th patch to add more debugging in skb_checksum_help()
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -50,6 +50,7 @@
 #include <linux/hashtable.h>
 #include <linux/rbtree.h>
 #include <net/net_trackers.h>
+#include <net/net_debug.h>
 
 struct netpoll_info;
 struct device;
@@ -5071,81 +5072,9 @@ static inline const char *netdev_reg_state(const struct net_device *dev)
 	return " (unknown)";
 }
 
-__printf(3, 4) __cold
-void netdev_printk(const char *level, const struct net_device *dev,
-		   const char *format, ...);
-__printf(2, 3) __cold
-void netdev_emerg(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_alert(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_crit(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_err(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_warn(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_notice(const struct net_device *dev, const char *format, ...);
-__printf(2, 3) __cold
-void netdev_info(const struct net_device *dev, const char *format, ...);
-
-#define netdev_level_once(level, dev, fmt, ...)			\
-do {								\
-	static bool __section(".data.once") __print_once;	\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		netdev_printk(level, dev, fmt, ##__VA_ARGS__);	\
-	}							\
-} while (0)
-
-#define netdev_emerg_once(dev, fmt, ...) \
-	netdev_level_once(KERN_EMERG, dev, fmt, ##__VA_ARGS__)
-#define netdev_alert_once(dev, fmt, ...) \
-	netdev_level_once(KERN_ALERT, dev, fmt, ##__VA_ARGS__)
-#define netdev_crit_once(dev, fmt, ...) \
-	netdev_level_once(KERN_CRIT, dev, fmt, ##__VA_ARGS__)
-#define netdev_err_once(dev, fmt, ...) \
-	netdev_level_once(KERN_ERR, dev, fmt, ##__VA_ARGS__)
-#define netdev_warn_once(dev, fmt, ...) \
-	netdev_level_once(KERN_WARNING, dev, fmt, ##__VA_ARGS__)
-#define netdev_notice_once(dev, fmt, ...) \
-	netdev_level_once(KERN_NOTICE, dev, fmt, ##__VA_ARGS__)
-#define netdev_info_once(dev, fmt, ...) \
-	netdev_level_once(KERN_INFO, dev, fmt, ##__VA_ARGS__)
-
 #define MODULE_ALIAS_NETDEV(device) \
 	MODULE_ALIAS("netdev-" device)
 
-#if defined(CONFIG_DYNAMIC_DEBUG) || \
-	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
-#define netdev_dbg(__dev, format, args...)			\
-do {								\
-	dynamic_netdev_dbg(__dev, format, ##args);		\
-} while (0)
-#elif defined(DEBUG)
-#define netdev_dbg(__dev, format, args...)			\
-	netdev_printk(KERN_DEBUG, __dev, format, ##args)
-#else
-#define netdev_dbg(__dev, format, args...)			\
-({								\
-	if (0)							\
-		netdev_printk(KERN_DEBUG, __dev, format, ##args); \
-})
-#endif
-
-#if defined(VERBOSE_DEBUG)
-#define netdev_vdbg	netdev_dbg
-#else
-
-#define netdev_vdbg(dev, format, args...)			\
-({								\
-	if (0)							\
-		netdev_printk(KERN_DEBUG, dev, format, ##args);	\
-	0;							\
-})
-#endif
-
 /*
  * netdev_WARN() acts like dev_printk(), but with the key difference
  * of using a WARN/WARN_ON to get the message out, including the
@@ -5159,74 +5088,6 @@ do {								\
 	WARN_ONCE(1, "netdevice: %s%s: " format, netdev_name(dev),	\
 		  netdev_reg_state(dev), ##args)
 
-/* netif printk helpers, similar to netdev_printk */
-
-#define netif_printk(priv, type, level, dev, fmt, args...)	\
-do {					  			\
-	if (netif_msg_##type(priv))				\
-		netdev_printk(level, (dev), fmt, ##args);	\
-} while (0)
-
-#define netif_level(level, priv, type, dev, fmt, args...)	\
-do {								\
-	if (netif_msg_##type(priv))				\
-		netdev_##level(dev, fmt, ##args);		\
-} while (0)
-
-#define netif_emerg(priv, type, dev, fmt, args...)		\
-	netif_level(emerg, priv, type, dev, fmt, ##args)
-#define netif_alert(priv, type, dev, fmt, args...)		\
-	netif_level(alert, priv, type, dev, fmt, ##args)
-#define netif_crit(priv, type, dev, fmt, args...)		\
-	netif_level(crit, priv, type, dev, fmt, ##args)
-#define netif_err(priv, type, dev, fmt, args...)		\
-	netif_level(err, priv, type, dev, fmt, ##args)
-#define netif_warn(priv, type, dev, fmt, args...)		\
-	netif_level(warn, priv, type, dev, fmt, ##args)
-#define netif_notice(priv, type, dev, fmt, args...)		\
-	netif_level(notice, priv, type, dev, fmt, ##args)
-#define netif_info(priv, type, dev, fmt, args...)		\
-	netif_level(info, priv, type, dev, fmt, ##args)
-
-#if defined(CONFIG_DYNAMIC_DEBUG) || \
-	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
-#define netif_dbg(priv, type, netdev, format, args...)		\
-do {								\
-	if (netif_msg_##type(priv))				\
-		dynamic_netdev_dbg(netdev, format, ##args);	\
-} while (0)
-#elif defined(DEBUG)
-#define netif_dbg(priv, type, dev, format, args...)		\
-	netif_printk(priv, type, KERN_DEBUG, dev, format, ##args)
-#else
-#define netif_dbg(priv, type, dev, format, args...)			\
-({									\
-	if (0)								\
-		netif_printk(priv, type, KERN_DEBUG, dev, format, ##args); \
-	0;								\
-})
-#endif
-
-/* if @cond then downgrade to debug, else print at @level */
-#define netif_cond_dbg(priv, type, netdev, cond, level, fmt, args...)     \
-	do {                                                              \
-		if (cond)                                                 \
-			netif_dbg(priv, type, netdev, fmt, ##args);       \
-		else                                                      \
-			netif_ ## level(priv, type, netdev, fmt, ##args); \
-	} while (0)
-
-#if defined(VERBOSE_DEBUG)
-#define netif_vdbg	netif_dbg
-#else
-#define netif_vdbg(priv, type, dev, format, args...)		\
-({								\
-	if (0)							\
-		netif_printk(priv, type, KERN_DEBUG, dev, format, ##args); \
-	0;							\
-})
-#endif
-
 /*
  *	The list of packet types we will receive (as opposed to discard)
  *	and the routines to invoke.

include/linux/skbuff.h

@@ -42,6 +42,7 @@
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 #include <linux/netfilter/nf_conntrack_common.h>
 #endif
+#include <net/net_debug.h>
 
 /**
  * DOC: skb checksums
@@ -2904,6 +2905,7 @@ static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
 
 static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
 {
+	DEBUG_NET_WARN_ON_ONCE(!skb_transport_header_was_set(skb));
 	return skb->head + skb->transport_header;
 }
 

include/net/net_debug.h

+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NET_DEBUG_H
+#define _LINUX_NET_DEBUG_H
+
+#include <linux/bug.h>
+#include <linux/kern_levels.h>
+
+struct net_device;
+
+__printf(3, 4) __cold
+void netdev_printk(const char *level, const struct net_device *dev,
+		   const char *format, ...);
+__printf(2, 3) __cold
+void netdev_emerg(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_alert(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_crit(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_err(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_warn(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_notice(const struct net_device *dev, const char *format, ...);
+__printf(2, 3) __cold
+void netdev_info(const struct net_device *dev, const char *format, ...);
+
+#define netdev_level_once(level, dev, fmt, ...)			\
+do {								\
+	static bool __section(".data.once") __print_once;	\
+								\
+	if (!__print_once) {					\
+		__print_once = true;				\
+		netdev_printk(level, dev, fmt, ##__VA_ARGS__);	\
+	}							\
+} while (0)
+
+#define netdev_emerg_once(dev, fmt, ...) \
+	netdev_level_once(KERN_EMERG, dev, fmt, ##__VA_ARGS__)
+#define netdev_alert_once(dev, fmt, ...) \
+	netdev_level_once(KERN_ALERT, dev, fmt, ##__VA_ARGS__)
+#define netdev_crit_once(dev, fmt, ...) \
+	netdev_level_once(KERN_CRIT, dev, fmt, ##__VA_ARGS__)
+#define netdev_err_once(dev, fmt, ...) \
+	netdev_level_once(KERN_ERR, dev, fmt, ##__VA_ARGS__)
+#define netdev_warn_once(dev, fmt, ...) \
+	netdev_level_once(KERN_WARNING, dev, fmt, ##__VA_ARGS__)
+#define netdev_notice_once(dev, fmt, ...) \
+	netdev_level_once(KERN_NOTICE, dev, fmt, ##__VA_ARGS__)
+#define netdev_info_once(dev, fmt, ...) \
+	netdev_level_once(KERN_INFO, dev, fmt, ##__VA_ARGS__)
+
+#if defined(CONFIG_DYNAMIC_DEBUG) || \
+	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
+#define netdev_dbg(__dev, format, args...)			\
+do {								\
+	dynamic_netdev_dbg(__dev, format, ##args);		\
+} while (0)
+#elif defined(DEBUG)
+#define netdev_dbg(__dev, format, args...)			\
+	netdev_printk(KERN_DEBUG, __dev, format, ##args)
+#else
+#define netdev_dbg(__dev, format, args...)			\
+({								\
+	if (0)							\
+		netdev_printk(KERN_DEBUG, __dev, format, ##args); \
+})
+#endif
+
+#if defined(VERBOSE_DEBUG)
+#define netdev_vdbg	netdev_dbg
+#else
+
+#define netdev_vdbg(dev, format, args...)			\
+({								\
+	if (0)							\
+		netdev_printk(KERN_DEBUG, dev, format, ##args);	\
+	0;							\
+})
+#endif
+
+/* netif printk helpers, similar to netdev_printk */
+
+#define netif_printk(priv, type, level, dev, fmt, args...)	\
+do {					  			\
+	if (netif_msg_##type(priv))				\
+		netdev_printk(level, (dev), fmt, ##args);	\
+} while (0)
+
+#define netif_level(level, priv, type, dev, fmt, args...)	\
+do {								\
+	if (netif_msg_##type(priv))				\
+		netdev_##level(dev, fmt, ##args);		\
+} while (0)
+
+#define netif_emerg(priv, type, dev, fmt, args...)		\
+	netif_level(emerg, priv, type, dev, fmt, ##args)
+#define netif_alert(priv, type, dev, fmt, args...)		\
+	netif_level(alert, priv, type, dev, fmt, ##args)
+#define netif_crit(priv, type, dev, fmt, args...)		\
+	netif_level(crit, priv, type, dev, fmt, ##args)
+#define netif_err(priv, type, dev, fmt, args...)		\
+	netif_level(err, priv, type, dev, fmt, ##args)
+#define netif_warn(priv, type, dev, fmt, args...)		\
+	netif_level(warn, priv, type, dev, fmt, ##args)
+#define netif_notice(priv, type, dev, fmt, args...)		\
+	netif_level(notice, priv, type, dev, fmt, ##args)
+#define netif_info(priv, type, dev, fmt, args...)		\
+	netif_level(info, priv, type, dev, fmt, ##args)
+
+#if defined(CONFIG_DYNAMIC_DEBUG) || \
+	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
+#define netif_dbg(priv, type, netdev, format, args...)		\
+do {								\
+	if (netif_msg_##type(priv))				\
+		dynamic_netdev_dbg(netdev, format, ##args);	\
+} while (0)
+#elif defined(DEBUG)
+#define netif_dbg(priv, type, dev, format, args...)		\
+	netif_printk(priv, type, KERN_DEBUG, dev, format, ##args)
+#else
+#define netif_dbg(priv, type, dev, format, args...)			\
+({									\
+	if (0)								\
+		netif_printk(priv, type, KERN_DEBUG, dev, format, ##args); \
+	0;								\
+})
+#endif
+
+/* if @cond then downgrade to debug, else print at @level */
+#define netif_cond_dbg(priv, type, netdev, cond, level, fmt, args...)     \
+	do {                                                              \
+		if (cond)                                                 \
+			netif_dbg(priv, type, netdev, fmt, ##args);       \
+		else                                                      \
+			netif_ ## level(priv, type, netdev, fmt, ##args); \
+	} while (0)
+
+#if defined(VERBOSE_DEBUG)
+#define netif_vdbg	netif_dbg
+#else
+#define netif_vdbg(priv, type, dev, format, args...)		\
+({								\
+	if (0)							\
+		netif_printk(priv, type, KERN_DEBUG, dev, format, ##args); \
+	0;							\
+})
+#endif
+
+
+#if defined(CONFIG_DEBUG_NET)
+#define DEBUG_NET_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
+#else
+#define DEBUG_NET_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
+#endif
+
+#endif	/* _LINUX_NET_DEBUG_H */

net/Kconfig.debug

@@ -17,3 +17,10 @@ config NET_NS_REFCNT_TRACKER
 	help
 	  Enable debugging feature to track netns references.
 	  This adds memory and cpu costs.
+
+config DEBUG_NET
+	bool "Add generic networking debug"
+	depends on DEBUG_KERNEL
+	help
+	  Enable extra sanity checks in networking.
+	  This is mostly used by fuzzers, but is safe to select.

net/core/dev.c

@@ -3265,12 +3265,18 @@ int skb_checksum_help(struct sk_buff *skb)
 	}
 
 	offset = skb_checksum_start_offset(skb);
-	BUG_ON(offset >= skb_headlen(skb));
+	ret = -EINVAL;
+	if (WARN_ON_ONCE(offset >= skb_headlen(skb))) {
+		DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
+		goto out;
+	}
 	csum = skb_checksum(skb, offset, skb->len - offset, 0);
 
 	offset += skb->csum_offset;
-	BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));
-
+	if (WARN_ON_ONCE(offset + sizeof(__sum16) > skb_headlen(skb))) {
+		DO_ONCE_LITE(skb_dump, KERN_ERR, skb, false);
+		goto out;
+	}
 	ret = skb_ensure_writable(skb, offset + sizeof(__sum16));
 	if (ret)
 		goto out;