tls: fix use-after-free on failed backlog decryption

When the decrypt request goes to the backlog and crypto_aead_decrypt
returns -EBUSY, tls_do_decryption will wait until all async
decryptions have completed. If one of them fails, tls_do_decryption
will return -EBADMSG and tls_decrypt_sg jumps to the error path,
releasing all the pages. But the pages have been passed to the async
callback, and have already been released by tls_decrypt_done.

The only true async case is when crypto_aead_decrypt returns
 -EINPROGRESS. With -EBUSY, we already waited so we can tell
tls_sw_recvmsg that the data is available for immediate copy, but we
need to notify tls_decrypt_sg (via the new ->async_done flag) that the
memory has already been released.

Fixes: 859054147318 ("net: tls: handle backlogging of crypto requests")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/4755dd8d9bebdefaa19ce1439b833d6199d4364c.1709132643.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 1fd37fe13ffd8f12bb614d9fef8ab5d3ae363568..211f57164cb611fd2665f682906be96aa35463ed 100644 (file)
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -52,6 +52,7 @@ struct tls_decrypt_arg {
        struct_group(inargs,
        bool zc;
        bool async;
+       bool async_done;
        u8 tail;
        );
 
@@ -286,15 +287,18 @@ static int tls_do_decryption(struct sock *sk,
        }
 
        ret = crypto_aead_decrypt(aead_req);
+       if (ret == -EINPROGRESS)
+               return 0;
+
        if (ret == -EBUSY) {
                ret = tls_decrypt_async_wait(ctx);
-               ret = ret ?: -EINPROGRESS;
-       }
-       if (ret == -EINPROGRESS) {
-               return 0;
-       } else if (darg->async) {
-               atomic_dec(&ctx->decrypt_pending);
+               darg->async_done = true;
+               /* all completions have run, we're not doing async anymore */
+               darg->async = false;
+               return ret;
        }
+
+       atomic_dec(&ctx->decrypt_pending);
        darg->async = false;
 
        return ret;
@@ -1593,8 +1597,11 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
        /* Prepare and submit AEAD request */
        err = tls_do_decryption(sk, sgin, sgout, dctx->iv,
                                data_len + prot->tail_size, aead_req, darg);
-       if (err)
+       if (err) {
+               if (darg->async_done)
+                       goto exit_free_skb;
                goto exit_free_pages;
+       }
 
        darg->skb = clear_skb ?: tls_strp_msg(ctx);
        clear_skb = NULL;
@@ -1606,6 +1613,9 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
                return err;
        }
 
+       if (unlikely(darg->async_done))
+               return 0;
+
        if (prot->tail_size)
                darg->tail = dctx->tail;