net: skmsg: fix TLS 1.3 crash with full sk_msg

[ Upstream commit 031097d9e079e40dce401031d1012e83d80eaf01 ]

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 <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
index ce7055259877b7f42a80a55508700d3dec5833e7..da4caff7efa4028e092895e0a4a24e3f0f88a565 100644 (file)
--- 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,
@@ -29,11 +30,13 @@ struct sk_msg_sg {
        u32                             size;
        u32                             copybreak;
        bool                            copy[MAX_MSG_FRAGS];
-       /* 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];
 };
 
 /* UAPI in filter.c depends on struct sk_msg_sg being first element. */
@@ -141,13 +144,13 @@ 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)
@@ -155,7 +158,7 @@ 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)
 
@@ -172,9 +175,9 @@ 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,
@@ -195,14 +198,11 @@ 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);
 }
 

diff --git a/net/core/filter.c b/net/core/filter.c
index 3fed5755494bd39cf55ca1806ead67609ae8b587..6d0111bfdb4afcd1492267ce1445d0f86dd8fda0 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2299,7 +2299,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
        WARN_ON_ONCE(last_sge == first_sge);
        shift = last_sge > first_sge ?
                last_sge - first_sge - 1 :
-               MAX_SKB_FRAGS - first_sge + last_sge - 1;
+               NR_MSG_FRAG_IDS - first_sge + last_sge - 1;
        if (!shift)
                goto out;
 
@@ -2308,8 +2308,8 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
        do {
                u32 move_from;
 
-               if (i + shift >= MAX_MSG_FRAGS)
-                       move_from = i + shift - MAX_MSG_FRAGS;
+               if (i + shift >= NR_MSG_FRAG_IDS)
+                       move_from = i + shift - NR_MSG_FRAG_IDS;
                else
                        move_from = i + shift;
                if (move_from == msg->sg.end)
@@ -2323,7 +2323,7 @@ BPF_CALL_4(bpf_msg_pull_data, struct sk_msg *, msg, u32, start,
        } while (1);
 
        msg->sg.end = msg->sg.end - shift > msg->sg.end ?
-                     msg->sg.end - shift + MAX_MSG_FRAGS :
+                     msg->sg.end - shift + NR_MSG_FRAG_IDS :
                      msg->sg.end - shift;
 out:
        msg->data = sg_virt(&msg->sg.data[first_sge]) + start - offset;

diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index ad31e4e53d0a7186e9d2b7e5663c4c7bfa569fc3..0675d022584e6984629e74f55c02ee477a773592 100644 (file)
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -421,7 +421,7 @@ static int sk_psock_skb_ingress(struct sk_psock *psock, struct sk_buff *skb)
        copied = skb->len;
        msg->sg.start = 0;
        msg->sg.size = copied;
-       msg->sg.end = num_sge == MAX_MSG_FRAGS ? 0 : num_sge;
+       msg->sg.end = num_sge;
        msg->skb = skb;
 
        sk_psock_queue_msg(psock, msg);

diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 8a56e09cfb0ed3ebf03795ae4b5d1eb3f04221ba..e38705165ac9bd48910348169fc9904c41fb48dc 100644 (file)
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -301,7 +301,7 @@ EXPORT_SYMBOL_GPL(tcp_bpf_sendmsg_redir);
 static int tcp_bpf_send_verdict(struct sock *sk, struct sk_psock *psock,
                                struct sk_msg *msg, int *copied, int flags)
 {
-       bool cork = false, enospc = msg->sg.start == msg->sg.end;
+       bool cork = false, enospc = sk_msg_full(msg);
        struct sock *sk_redir;
        u32 tosend, delta = 0;
        int ret;