[PATCH net] tls: fix skb_to_sgvec returning unhandled error.

[Doron Roberts-Kedes]

The current code does not inspect the return value of skb_to_sgvec. This
can cause a nullptr kernel panic when the malformed sgvec is passed into
the crypto request.

Checking the return value of skb_to_sgvec and skipping decryption if it
is negative fixes this problem.

Fixes: c46234ebb4d1 ("tls: RX path for ktls")
Acked-by: Dave Watson <davejwat...@fb.com>
Signed-off-by: Doron Roberts-Kedes <doro...@fb.com>
---
 net/tls/tls_sw.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 173d8b89072d..b6e118499083 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -701,6 +701,10 @@ static int decrypt_skb(struct sock *sk, struct sk_buff 
*skb,
        nsg = skb_to_sgvec(skb, &sgin[1],
                           rxm->offset + tls_ctx->rx.prepend_size,
                           rxm->full_len - tls_ctx->rx.prepend_size);
+       if (nsg < 0) {
+               ret = nsg;
+               goto out;
+       }
 
        tls_make_aad(ctx->rx_aad_ciphertext,
                     rxm->full_len - tls_ctx->rx.overhead_size,
@@ -712,6 +716,7 @@ static int decrypt_skb(struct sock *sk, struct sk_buff *skb,
                                rxm->full_len - tls_ctx->rx.overhead_size,
                                skb, sk->sk_allocation);
 
+out:
        if (sgin != &sgin_arr[0])
                kfree(sgin);
 
-- 
2.17.1