CVE-2026-74611tls: rx: restore msg_iter before TLS 1.3 optimistic retry

Official description

In the Linux kernel, the following vulnerability has been resolved: tls: rx: restore msg_iter before TLS 1.3 optimistic retry 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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/97004f3c17371ee1b259887298711e0604666688
• https://git.kernel.org/stable/c/c71bacacd59166adbea423a04e7474b0e8245b84
• https://git.kernel.org/stable/c/3c4e21b1bf8e666a1c141e0f5813ece929570deb
• https://git.kernel.org/stable/c/68787940274ec89f41dc91b1a68ee1a16a90735f
• https://git.kernel.org/stable/c/3c837266a734e2a22b24d2d567404a501d405835
• https://git.kernel.org/stable/c/1c8629651cb54f7b51db8fc0b1a9944e4a4b0f5e