FAILED: patch "[PATCH] tls: rx: restore msg_iter before TLS 1.3 optimistic retry" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 1c8629651cb54f7b51db8fc0b1a9944e4a4b0f5e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026081718-rudder-backlight-388d@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1c8629651cb54f7b51db8fc0b1a9944e4a4b0f5e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= <[email protected]>
Date: Tue, 4 Aug 2026 12:55:28 +0000
Subject: [PATCH] tls: rx: restore msg_iter before TLS 1.3 optimistic retry
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tls_decrypt_sg() advances msg->msg_iter when it maps user pages for the optimistic TLS 1.3 zero-copy path. If the decrypted record turns out not to be unpadded application data, tls_decrypt_sw() retries into a kernel skb, but leaves the iterator advanced.

The subsequent copy from the skb then writes decrypted bytes again at a later point in the caller iovecs while recvmsg() reports only the post-retry length. A TLS peer can trigger this after the receiver enables TLS_RX_EXPECT_NO_PAD.

Revert the iterator by the number of bytes consumed by the optimistic mapping before retrying without zero-copy.

Add a selftest which sends a TLS 1.3 control record with TLS_RX_EXPECT_NO_PAD enabled and verifies that recvmsg() does not overwrite later iovecs beyond the returned length.

index d2e399be8ef6..133ed7c89402 100644
@@ -1456,6 +1456,8 @@ tls_decrypt_sw(struct sock *sk, struct tls_context *tls_ctx,
 	/* If opportunistic TLS 1.3 ZC failed retry without ZC */
 	if (unlikely(darg->zc && prot->version == TLS_1_3_VERSION &&
 		     darg->tail != TLS_RECORD_TYPE_DATA)) {
+		iov_iter_revert(&msg->msg_iter, strp_msg(darg->skb)->full_len -
+				prot->overhead_size);
 		darg->zc = false;
 		if (!darg->tail)
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXNOPADVIOL);