From 031097d9e079e40dce401031d1012e83d80eaf01 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 27 Nov 2019 12:16:41 -0800 Subject: net: skmsg: fix TLS 1.3 crash with full sk_msg TLS 1.3 started using the entry at the end of the SG array for chaining-in the single byte content type entry. This mostly works: [ E E E E E E . . ] ^ ^ start end E < content type / [ E E E E E E C . ] ^ ^ start end (Where E denotes a populated SG entry; C denotes a chaining entry.) If the array is full, however, the end will point to the start: [ E E E E E E E E ] ^ start end And we end up overwriting the start: E < content type / [ C E E E E E E E ] ^ start end The sg array is supposed to be a circular buffer with start and end markers pointing anywhere. In case where start > end (i.e. the circular buffer has "wrapped") there is an extra entry reserved at the end to chain the two halves together. [ E E E E E E . . l ] (Where l is the reserved entry for "looping" back to front. As suggested by John, let's reserve another entry for chaining SG entries after the main circular buffer. Note that this entry has to be pointed to by the end entry so its position is not fixed. Examples of full messages: [ E E E E E E E E . l ] ^ ^ start end <---------------. [ E E . E E E E E E l ] ^ ^ end start Now the end will always point to an unused entry, so TLS 1.3 can always use it. Fixes: 130b392c6cd6 ("net: tls: Add tls 1.3 support") Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- include/linux/skmsg.h | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) (limited to 'include') 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 #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); } -- cgit v1.2.3 From 9e5ffed37df68d0ccfb2fdc528609e23a1e70ebe Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 27 Nov 2019 12:16:43 -0800 Subject: net/tls: remove the dead inplace_crypto code Looks like when BPF support was added by commit d3b18ad31f93 ("tls: add bpf support to sk_msg handling") and commit d829e9c4112b ("tls: convert to generic sk_msg interface") it broke/removed the support for in-place crypto as added by commit 4e6d47206c32 ("tls: Add support for inplace records encryption"). The inplace_crypto member of struct tls_rec is dead, inited to zero, and sometimes set to zero again. It used to be set to 1 when record was allocated, but the skmsg code doesn't seem to have been written with the idea of in-place crypto in mind. Since non trivial effort is required to bring the feature back and we don't really have the HW to measure the benefit just remove the left over support for now to avoid confusing readers. Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- include/net/tls.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include') diff --git a/include/net/tls.h b/include/net/tls.h index 6ed91e82edd0..9d32f7ce6b31 100644 --- a/include/net/tls.h +++ b/include/net/tls.h @@ -100,7 +100,6 @@ struct tls_rec { struct list_head list; int tx_ready; int tx_flags; - int inplace_crypto; struct sk_msg msg_plaintext; struct sk_msg msg_encrypted; -- cgit v1.2.3 From c5daa6cccdc2f94aca2c9b3fa5f94e4469997293 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Wed, 27 Nov 2019 12:16:44 -0800 Subject: net/tls: use sg_next() to walk sg entries Partially sent record cleanup path increments an SG entry directly instead of using sg_next(). This should not be a problem today, as encrypted messages should be always allocated as arrays. But given this is a cleanup path it's easy to miss was this ever to change. Use sg_next(), and simplify the code. Signed-off-by: Jakub Kicinski Reviewed-by: Simon Horman Signed-off-by: David S. Miller --- include/net/tls.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/net/tls.h b/include/net/tls.h index 9d32f7ce6b31..df630f5fc723 100644 --- a/include/net/tls.h +++ b/include/net/tls.h @@ -376,7 +376,7 @@ int tls_push_sg(struct sock *sk, struct tls_context *ctx, int flags); int tls_push_partial_record(struct sock *sk, struct tls_context *ctx, int flags); -bool tls_free_partial_record(struct sock *sk, struct tls_context *ctx); +void tls_free_partial_record(struct sock *sk, struct tls_context *ctx); static inline struct tls_msg *tls_msg(struct sk_buff *skb) { -- cgit v1.2.3