Patch "tls: fix use-after-free on failed backlog decryption" has been added to the 6.7-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tls-fix-use-after-free-on-failed-backlog-decryption.patch
and it can be found in the queue-6.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4867fcabeff59551e125bbc057c72e230550a1ad
Author: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Date:   Wed Feb 28 23:44:00 2024 +0100

    tls: fix use-after-free on failed backlog decryption
    
    [ Upstream commit 13114dc5543069f7b97991e3b79937b6da05f5b0 ]
    
    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@xxxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/4755dd8d9bebdefaa19ce1439b833d6199d4364c.1709132643.git.sd@xxxxxxxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 1fd37fe13ffd8..211f57164cb61 100644
--- 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;