Merge branch 'net-tls-fix-scatter-gather-list-issues'

Jakub Kicinski says:

====================
net: tls: fix scatter-gather list issues

This series kicked of by a syzbot report fixes three issues around
scatter gather handling in the TLS code. First patch fixes a use-
-after-free situation which may occur if record was freed on error.
This could have already happened in BPF paths, and patch 2 now makes
the same condition occur in non-BPF code.

Patch 2 fixes the problem spotted by syzbot. If encryption failed
we have to clean the end markings from scatter gather list. As
suggested by John the patch frees the record entirely and caller
may retry copying data from user space buffer again.

Third patch fixes a bug in the TLS 1.3 code spotted while working
on patch 2. TLS 1.3 may effectively overflow the SG list which
leads to the BUG() in sg_page() being triggered.

Patch 4 adds a test case which triggers this bug reliably.

Next two patches are small cleanups of dead code and code which
makes dangerous assumptions.

Last but not least two minor improvements to the sockmap tests.

Tested:
 - bpf/test_sockmap
 - net/tls
 - syzbot repro (which used error injection, hence no direct
   selftest is added to preserve it).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 14 deletions

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index 6cb077b646a5..ef7031f8a304 100644
--- a/include/linux/skmsg.h
+++ b/include/linux/skmsg.h
@@ -14,6 +14,7 @@
 #include <net/strparser.h>
 
 #define MAX_MSG_FRAGS			MAX_SKB_FRAGS
+#define NR_MSG_FRAG_IDS			(MAX_MSG_FRAGS + 1)
 
 enum __sk_action {
 	__SK_DROP = 0,
@@ -29,13 +30,15 @@ struct sk_msg_sg {
 	u32				size;
 	u32				copybreak;
 	unsigned long			copy;
-	/* The extra element is used for chaining the front and sections when
-	 * the list becomes partitioned (e.g. end < start). The crypto APIs
-	 * require the chaining.
+	/* The extra two elements:
+	 * 1) used for chaining the front and sections when the list becomes
+	 *    partitioned (e.g. end < start). The crypto APIs require the
+	 *    chaining;
+	 * 2) to chain tailer SG entries after the message.
 	 */
-	struct scatterlist		data[MAX_MSG_FRAGS + 1];
+	struct scatterlist		data[MAX_MSG_FRAGS + 2];
 };
-static_assert(BITS_PER_LONG >= MAX_MSG_FRAGS);
+static_assert(BITS_PER_LONG >= NR_MSG_FRAG_IDS);
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
 struct sk_msg {
@@ -142,13 +145,13 @@ static inline void sk_msg_apply_bytes(struct sk_psock *psock, u32 bytes)
 
 static inline u32 sk_msg_iter_dist(u32 start, u32 end)
 {
-	return end >= start ? end - start : end + (MAX_MSG_FRAGS - start);
+	return end >= start ? end - start : end + (NR_MSG_FRAG_IDS - start);
 }
 
 #define sk_msg_iter_var_prev(var)			\
 	do {						\
 		if (var == 0)				\
-			var = MAX_MSG_FRAGS - 1;	\
+			var = NR_MSG_FRAG_IDS - 1;	\
 		else					\
 			var--;				\
 	} while (0)
@@ -156,7 +159,7 @@ static inline u32 sk_msg_iter_dist(u32 start, u32 end)
 #define sk_msg_iter_var_next(var)			\
 	do {						\
 		var++;					\
-		if (var == MAX_MSG_FRAGS)		\
+		if (var == NR_MSG_FRAG_IDS)		\
 			var = 0;			\
 	} while (0)
 
@@ -173,9 +176,9 @@ static inline void sk_msg_clear_meta(struct sk_msg *msg)
 
 static inline void sk_msg_init(struct sk_msg *msg)
 {
-	BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != MAX_MSG_FRAGS);
+	BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != NR_MSG_FRAG_IDS);
 	memset(msg, 0, sizeof(*msg));
-	sg_init_marker(msg->sg.data, MAX_MSG_FRAGS);
+	sg_init_marker(msg->sg.data, NR_MSG_FRAG_IDS);
 }
 
 static inline void sk_msg_xfer(struct sk_msg *dst, struct sk_msg *src,
@@ -196,14 +199,11 @@ static inline void sk_msg_xfer_full(struct sk_msg *dst, struct sk_msg *src)
 
 static inline bool sk_msg_full(const struct sk_msg *msg)
 {
-	return (msg->sg.end == msg->sg.start) && msg->sg.size;
+	return sk_msg_iter_dist(msg->sg.start, msg->sg.end) == MAX_MSG_FRAGS;
 }
 
 static inline u32 sk_msg_elem_used(const struct sk_msg *msg)
 {
-	if (sk_msg_full(msg))
-		return MAX_MSG_FRAGS;
-
 	return sk_msg_iter_dist(msg->sg.start, msg->sg.end);
 }