From 6370cc3bbd8a0f9bf975b013781243ab147876c6 Mon Sep 17 00:00:00 2001 From: Aleksandr Nogikh Date: Thu, 29 Oct 2020 17:36:19 +0000 Subject: net: add kcov handle to skb extensions Remote KCOV coverage collection enables coverage-guided fuzzing of the code that is not reachable during normal system call execution. It is especially helpful for fuzzing networking subsystems, where it is common to perform packet handling in separate work queues even for the packets that originated directly from the user space. Enable coverage-guided frame injection by adding kcov remote handle to skb extensions. Default initialization in __alloc_skb and __build_skb_around ensures that no socket buffer that was generated during a system call will be missed. Code that is of interest and that performs packet processing should be annotated with kcov_remote_start()/kcov_remote_stop(). An alternative approach is to determine kcov_handle solely on the basis of the device/interface that received the specific socket buffer. However, in this case it would be impossible to distinguish between packets that originated during normal background network processes or were intentionally injected from the user space. Signed-off-by: Aleksandr Nogikh Acked-by: Willem de Bruijn Signed-off-by: Jakub Kicinski --- include/linux/skbuff.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a828cf99c521..2d01b2bbb746 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -4150,6 +4150,9 @@ enum skb_ext_id { #endif #if IS_ENABLED(CONFIG_MPTCP) SKB_EXT_MPTCP, +#endif +#if IS_ENABLED(CONFIG_KCOV) + SKB_EXT_KCOV_HANDLE, #endif SKB_EXT_NUM, /* must be last */ }; @@ -4605,5 +4608,35 @@ static inline void skb_reset_redirect(struct sk_buff *skb) #endif } +#ifdef CONFIG_KCOV +static inline void skb_set_kcov_handle(struct sk_buff *skb, + const u64 kcov_handle) +{ + /* Do not allocate skb extensions only to set kcov_handle to zero + * (as it is zero by default). However, if the extensions are + * already allocated, update kcov_handle anyway since + * skb_set_kcov_handle can be called to zero a previously set + * value. + */ + if (skb_has_extensions(skb) || kcov_handle) { + u64 *kcov_handle_ptr = skb_ext_add(skb, SKB_EXT_KCOV_HANDLE); + + if (kcov_handle_ptr) + *kcov_handle_ptr = kcov_handle; + } +} + +static inline u64 skb_get_kcov_handle(struct sk_buff *skb) +{ + u64 *kcov_handle = skb_ext_find(skb, SKB_EXT_KCOV_HANDLE); + + return kcov_handle ? *kcov_handle : 0; +} +#else +static inline void skb_set_kcov_handle(struct sk_buff *skb, + const u64 kcov_handle) { } +static inline u64 skb_get_kcov_handle(struct sk_buff *skb) { return 0; } +#endif /* CONFIG_KCOV */ + #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ -- cgit v1.3-14-g43fede From 97f53a08cba128a724ebbbf34778d3553d559816 Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Mon, 16 Nov 2020 13:21:08 -0800 Subject: net: linux/skbuff.h: combine SKB_EXTENSIONS + KCOV handling The previous Kconfig patch led to some other build errors as reported by the 0day bot and my own overnight build testing. These are all in when KCOV is enabled but SKB_EXTENSIONS is not enabled, so fix those by combining those conditions in the header file. Fixes: 6370cc3bbd8a ("net: add kcov handle to skb extensions") Fixes: 85ce50d337d1 ("net: kcov: don't select SKB_EXTENSIONS when there is no NET") Signed-off-by: Randy Dunlap Reported-by: kernel test robot Cc: Aleksandr Nogikh Cc: Willem de Bruijn Acked-by: Florian Westphal Link: https://lore.kernel.org/r/20201116212108.32465-1-rdunlap@infradead.org Signed-off-by: Jakub Kicinski --- include/linux/skbuff.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 2d01b2bbb746..0a1239819fd2 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -4608,7 +4608,7 @@ static inline void skb_reset_redirect(struct sk_buff *skb) #endif } -#ifdef CONFIG_KCOV +#if IS_ENABLED(CONFIG_KCOV) && IS_ENABLED(CONFIG_SKB_EXTENSIONS) static inline void skb_set_kcov_handle(struct sk_buff *skb, const u64 kcov_handle) { @@ -4636,7 +4636,7 @@ static inline u64 skb_get_kcov_handle(struct sk_buff *skb) static inline void skb_set_kcov_handle(struct sk_buff *skb, const u64 kcov_handle) { } static inline u64 skb_get_kcov_handle(struct sk_buff *skb) { return 0; } -#endif /* CONFIG_KCOV */ +#endif /* CONFIG_KCOV && CONFIG_SKB_EXTENSIONS */ #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ -- cgit v1.3-14-g43fede From fa69ee5aa48b5b52e8028c2eb486906e9998d081 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Wed, 25 Nov 2020 23:48:40 +0100 Subject: net: switch to storing KCOV handle directly in sk_buff It turns out that usage of skb extensions can cause memory leaks. Ido Schimmel reported: "[...] there are instances that blindly overwrite 'skb->extensions' by invoking skb_copy_header() after __alloc_skb()." Therefore, give up on using skb extensions for KCOV handle, and instead directly store kcov_handle in sk_buff. Fixes: 6370cc3bbd8a ("net: add kcov handle to skb extensions") Fixes: 85ce50d337d1 ("net: kcov: don't select SKB_EXTENSIONS when there is no NET") Fixes: 97f53a08cba1 ("net: linux/skbuff.h: combine SKB_EXTENSIONS + KCOV handling") Link: https://lore.kernel.org/linux-wireless/20201121160941.GA485907@shredder.lan/ Reported-by: Ido Schimmel Signed-off-by: Marco Elver Link: https://lore.kernel.org/r/20201125224840.2014773-1-elver@google.com Signed-off-by: Jakub Kicinski --- include/linux/skbuff.h | 37 +++++++++++++------------------------ lib/Kconfig.debug | 1 - net/core/skbuff.c | 6 ------ 3 files changed, 13 insertions(+), 31 deletions(-) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 0a1239819fd2..333bcdc39635 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -701,6 +701,7 @@ typedef unsigned char *sk_buff_data_t; * @transport_header: Transport layer header * @network_header: Network layer header * @mac_header: Link layer header + * @kcov_handle: KCOV remote handle for remote coverage collection * @tail: Tail pointer * @end: End pointer * @head: Head of buffer @@ -904,6 +905,10 @@ struct sk_buff { __u16 network_header; __u16 mac_header; +#ifdef CONFIG_KCOV + u64 kcov_handle; +#endif + /* private: */ __u32 headers_end[0]; /* public: */ @@ -4150,9 +4155,6 @@ enum skb_ext_id { #endif #if IS_ENABLED(CONFIG_MPTCP) SKB_EXT_MPTCP, -#endif -#if IS_ENABLED(CONFIG_KCOV) - SKB_EXT_KCOV_HANDLE, #endif SKB_EXT_NUM, /* must be last */ }; @@ -4608,35 +4610,22 @@ static inline void skb_reset_redirect(struct sk_buff *skb) #endif } -#if IS_ENABLED(CONFIG_KCOV) && IS_ENABLED(CONFIG_SKB_EXTENSIONS) static inline void skb_set_kcov_handle(struct sk_buff *skb, const u64 kcov_handle) { - /* Do not allocate skb extensions only to set kcov_handle to zero - * (as it is zero by default). However, if the extensions are - * already allocated, update kcov_handle anyway since - * skb_set_kcov_handle can be called to zero a previously set - * value. - */ - if (skb_has_extensions(skb) || kcov_handle) { - u64 *kcov_handle_ptr = skb_ext_add(skb, SKB_EXT_KCOV_HANDLE); - - if (kcov_handle_ptr) - *kcov_handle_ptr = kcov_handle; - } +#ifdef CONFIG_KCOV + skb->kcov_handle = kcov_handle; +#endif } static inline u64 skb_get_kcov_handle(struct sk_buff *skb) { - u64 *kcov_handle = skb_ext_find(skb, SKB_EXT_KCOV_HANDLE); - - return kcov_handle ? *kcov_handle : 0; -} +#ifdef CONFIG_KCOV + return skb->kcov_handle; #else -static inline void skb_set_kcov_handle(struct sk_buff *skb, - const u64 kcov_handle) { } -static inline u64 skb_get_kcov_handle(struct sk_buff *skb) { return 0; } -#endif /* CONFIG_KCOV && CONFIG_SKB_EXTENSIONS */ + return 0; +#endif +} #endif /* __KERNEL__ */ #endif /* _LINUX_SKBUFF_H */ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 826a205ffd1c..1d15cdaf1b89 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1879,7 +1879,6 @@ config KCOV depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS select DEBUG_FS select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC - select SKB_EXTENSIONS if NET help KCOV exposes kernel code coverage information in a form suitable for coverage-guided fuzzing (randomized testing). diff --git a/net/core/skbuff.c b/net/core/skbuff.c index ad98265f1dd1..90d3423e6017 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4210,9 +4210,6 @@ static const u8 skb_ext_type_len[] = { #if IS_ENABLED(CONFIG_MPTCP) [SKB_EXT_MPTCP] = SKB_EXT_CHUNKSIZEOF(struct mptcp_ext), #endif -#if IS_ENABLED(CONFIG_KCOV) - [SKB_EXT_KCOV_HANDLE] = SKB_EXT_CHUNKSIZEOF(u64), -#endif }; static __always_inline unsigned int skb_ext_total_length(void) @@ -4229,9 +4226,6 @@ static __always_inline unsigned int skb_ext_total_length(void) #endif #if IS_ENABLED(CONFIG_MPTCP) skb_ext_type_len[SKB_EXT_MPTCP] + -#endif -#if IS_ENABLED(CONFIG_KCOV) - skb_ext_type_len[SKB_EXT_KCOV_HANDLE] + #endif 0; } -- cgit v1.3-14-g43fede