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.ga485...@shredder.lan/
Reported-by: Ido Schimmel <ido...@idosch.org>
Signed-off-by: Marco Elver <el...@google.com>
---
include/linux/skbuff.h | 37 +++++++++++++------------------------
lib/Kconfig.debug | 1 -
net/core/skbuff.c | 12 +-----------
3 files changed, 14 insertions(+), 36 deletions(-)
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 ffe3dcc0ebea..070b1077d976 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -233,6 +233,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t
gfp_mask,
skb->end = skb->tail + size;
skb->mac_header = (typeof(skb->mac_header))~0U;
skb->transport_header = (typeof(skb->transport_header))~0U;
+ skb_set_kcov_handle(skb, kcov_common_handle());
/* make sure we initialize shinfo sequentially */
shinfo = skb_shinfo(skb);
@@ -249,9 +250,6 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t
gfp_mask,
fclones->skb2.fclone = SKB_FCLONE_CLONE;
}
-
- skb_set_kcov_handle(skb, kcov_common_handle());
-
out:
return skb;
nodata:
@@ -285,8 +283,6 @@ static struct sk_buff *__build_skb_around(struct sk_buff
*skb,
memset(shinfo, 0, offsetof(struct skb_shared_info, dataref));
atomic_set(&shinfo->dataref, 1);
- skb_set_kcov_handle(skb, kcov_common_handle());
-
return skb;
}
@@ -4208,9 +4204,6 @@ 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)
@@ -4227,9 +4220,6 @@ 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;
}
base-commit: 470dfd808ac4135f313967f9d3e107b87fc6a0b3
--
2.29.2.454.gaff20da3a2-goog
