net: tls: fix use-after-free with partial reads and async decrypt

tls_decrypt_sg doesn't take a reference on the pages from clear_skb,
so the put_page() in tls_decrypt_done releases them, and we trigger
a use-after-free in process_rx_list when we try to read from the
partially-read skb.

Fixes: fd31f3996af2 ("tls: rx: decrypt into a fresh skb")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 63bef56..a6eff21 100644 (file)
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -63,6 +63,7 @@ struct tls_decrypt_ctx {
        u8 iv[TLS_MAX_IV_SIZE];
        u8 aad[TLS_MAX_AAD_SIZE];
        u8 tail;
+       bool free_sgout;
        struct scatterlist sg[];
 };
 
@@ -187,7 +188,6 @@ static void tls_decrypt_done(void *data, int err)
        struct aead_request *aead_req = data;
        struct crypto_aead *aead = crypto_aead_reqtfm(aead_req);
        struct scatterlist *sgout = aead_req->dst;
-       struct scatterlist *sgin = aead_req->src;
        struct tls_sw_context_rx *ctx;
        struct tls_decrypt_ctx *dctx;
        struct tls_context *tls_ctx;
@@ -224,7 +224,7 @@ static void tls_decrypt_done(void *data, int err)
        }
 
        /* Free the destination pages if skb was not decrypted inplace */
-       if (sgout != sgin) {
+       if (dctx->free_sgout) {
                /* Skip the first S/G entry as it points to AAD */
                for_each_sg(sg_next(sgout), sg, UINT_MAX, pages) {
                        if (!sg)
@@ -1583,6 +1583,7 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
        } else if (out_sg) {
                memcpy(sgout, out_sg, n_sgout * sizeof(*sgout));
        }
+       dctx->free_sgout = !!pages;
 
        /* Prepare and submit AEAD request */
        err = tls_do_decryption(sk, sgin, sgout, dctx->iv,