[PATCH 6.7 043/162] tls: fix use-after-free on failed backlog decryption

Greg Kroah-Hartman
2024-03-04T21:28:50Z

From: Sabrina Dubroca <sd@queasysnail.net>

[ 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@queasysnail.net>
Link: https://lore.kernel.org/r/4755dd8d9bebdefaa19ce1439b833d6199d4364c.1709132643.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/tls/tls_sw.c | 24 +++++++++++++++++-------
1 file changed, 17 insertions(+), 7 deletions(-)

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;

--
2.43.0