netdev - [PATCH net 2/5] tls: fix use-after-free with partial reads and async decrypt

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Message-Id: <aa1a31a25c2d0121e039f34ee58a996ea9a130ad.1694018970.git.sd@queasysnail.net>
Date: Wed,  6 Sep 2023 19:08:32 +0200
From: Sabrina Dubroca <sd@...asysnail.net>
To: netdev@...r.kernel.org
Cc: Sabrina Dubroca <sd@...asysnail.net>,
	Dave Watson <davejwatson@...com>,
	Jakub Kicinski <kuba@...nel.org>,
	Vakul Garg <vakul.garg@....com>,
	Boris Pismenny <borisp@...dia.com>,
	John Fastabend <john.fastabend@...il.com>
Subject: [PATCH net 2/5] 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.

This can be seen with the recv_and_splice test case.

Fixes: fd31f3996af2 ("tls: rx: decrypt into a fresh skb")
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 net/tls/tls_sw.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index 4f3dd0403efb..f23cceaceb36 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -63,6 +63,7 @@ struct tls_decrypt_ctx {
 	u8 iv[MAX_IV_SIZE];
 	u8 aad[TLS_MAX_AAD_SIZE];
 	u8 tail;
+	bool put_outsg;
 	struct scatterlist sg[];
 };
 
@@ -221,7 +222,8 @@ static void tls_decrypt_done(void *data, int err)
 		for_each_sg(sg_next(sgout), sg, UINT_MAX, pages) {
 			if (!sg)
 				break;
-			put_page(sg_page(sg));
+			if (dctx->put_outsg)
+				put_page(sg_page(sg));
 		}
 	}
 
@@ -1549,6 +1551,8 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
 	if (err < 0)
 		goto exit_free;
 
+	dctx->put_outsg = false;
+
 	if (clear_skb) {
 		sg_init_table(sgout, n_sgout);
 		sg_set_buf(&sgout[0], dctx->aad, prot->aad_size);
@@ -1558,6 +1562,8 @@ static int tls_decrypt_sg(struct sock *sk, struct iov_iter *out_iov,
 		if (err < 0)
 			goto exit_free;
 	} else if (out_iov) {
+		dctx->put_outsg = true;
+
 		sg_init_table(sgout, n_sgout);
 		sg_set_buf(&sgout[0], dctx->aad, prot->aad_size);
 
-- 
2.40.1