net: tls: handle backlogging of crypto requests

commit 8590541473188741055d27b955db0777569438e3 upstream.

Since we're setting the CRYPTO_TFM_REQ_MAY_BACKLOG flag on our
requests to the crypto API, crypto_aead_{encrypt,decrypt} can return
 -EBUSY instead of -EINPROGRESS in valid situations. For example, when
the cryptd queue for AESNI is full (easy to trigger with an
artificially low cryptd.cryptd_max_cpu_qlen), requests will be enqueued
to the backlog but still processed. In that case, the async callback
will also be called twice: first with err == -EINPROGRESS, which it
seems we can just ignore, then with err == 0.

Compared to Sabrina's original patch this version uses the new
tls_*crypt_async_wait() helpers and converts the EBUSY to
EINPROGRESS to avoid having to modify all the error handling
paths. The handling is identical.

BUG=b/338196126
TEST=presubmit
RELEASE_NOTE=Fixed CVE-2024-26584 in the Linux kernel.

cos-patch: security-high
Fixes: a54667f6728c ("tls: Add support for encryption using async offload accelerator")
Fixes: 94524d8fc965 ("net/tls: Add support for async decryption of tls records")
Co-developed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/netdev/9681d1febfec295449a62300938ed2ae66983f28.1694018970.git.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>
[v5.15: fixed contextual merge-conflicts in tls_decrypt_done and tls_encrypt_done]
Cc: <stable@vger.kernel.org> # 5.15
Signed-off-by: Shaoying Xu <shaoyi@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 3ade391adc584f17b5570fd205de3ad029090368)
Signed-off-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Change-Id: I44faca450c7d722bd06ddf17b00406dd7b37033b
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/74297
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Oleksandr Tymoshenko <ovt@google.com>

net/tls/tls_sw.c

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index ffa8804..c17c3a1 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -175,6 +175,17 @@ static void tls_decrypt_done(struct crypto_async_request *req, int err)
 	struct sk_buff *skb;
 	unsigned int pages;
 
+	/* If requests get too backlogged crypto API returns -EBUSY and calls
+	 * ->complete(-EINPROGRESS) immediately followed by ->complete(0)
+	 * to make waiting for backlog to flush with crypto_wait_req() easier.
+	 * First wait converts -EBUSY -> -EINPROGRESS, and the second one
+	 * -EINPROGRESS -> 0.
+	 * We have a single struct crypto_async_request per direction, this
+	 * scheme doesn't help us, so just ignore the first ->complete().
+	 */
+	if (err == -EINPROGRESS)
+		return;
+
 	skb = (struct sk_buff *)req->data;
 	tls_ctx = tls_get_ctx(skb->sk);
 	ctx = tls_sw_ctx_rx(tls_ctx);
@@ -273,6 +284,10 @@ static int tls_do_decryption(struct sock *sk,
 	}
 
 	ret = crypto_aead_decrypt(aead_req);
+	if (ret == -EBUSY) {
+		ret = tls_decrypt_async_wait(ctx);
+		ret = ret ?: -EINPROGRESS;
+	}
 	if (ret == -EINPROGRESS) {
 		if (darg->async)
 			return 0;
@@ -454,6 +469,9 @@ static void tls_encrypt_done(struct crypto_async_request *req, int err)
 	struct sk_msg *msg_en;
 	struct tls_rec *rec;
 
+	if (err == -EINPROGRESS) /* see the comment in tls_decrypt_done() */
+		return;
+
 	rec = container_of(aead_req, struct tls_rec, aead_req);
 	msg_en = &rec->msg_encrypted;
 
@@ -547,6 +565,10 @@ static int tls_do_encryption(struct sock *sk,
 	atomic_inc(&ctx->encrypt_pending);
 
 	rc = crypto_aead_encrypt(aead_req);
+	if (rc == -EBUSY) {
+		rc = tls_encrypt_async_wait(ctx);
+		rc = rc ?: -EINPROGRESS;
+	}
 	if (!rc || rc != -EINPROGRESS) {
 		atomic_dec(&ctx->encrypt_pending);
 		sge->offset -= prot->prepend_size;