tls: handle data disappearing from under the TLS ULP

[ Upstream commit 6db015fc4b5d5f63a64a193f65d98da3a7fc811d ]

TLS expects that it owns the receive queue of the TCP socket.
This cannot be guaranteed in case the reader of the TCP socket
entered before the TLS ULP was installed, or uses some non-standard
read API (eg. zerocopy ones). Replace the WARN_ON() and a buggy
early exit (which leaves anchor pointing to a freed skb) with real
error handling. Wipe the parsing state and tell the reader to retry.

We already reload the anchor every time we (re)acquire the socket lock,
so the only condition we need to avoid is an out of bounds read
(not having enough bytes in the socket for previously parsed record len).

If some data was read from under TLS but there's enough in the queue
we'll reload and decrypt what is most likely not a valid TLS record.
Leading to some undefined behavior from TLS perspective (corrupting
a stream? missing an alert? missing an attack?) but no kernel crash
should take place.

BUG=b/440568380
TEST=presubmit
RELEASE_NOTE=Fixed KCTF-6db015f in the Linux kernel.

Reported-by: William Liu <will@willsroot.io>
Reported-by: Savino Dicanosa <savy@syst3mfailure.io>
Link: https://lore.kernel.org/tFjq_kf7sWIG3A7CrCg_egb8CVsT_gsmHAK0_wxDPJXfIzxFAMxqmLwp3MlU5EHiet0AwwJldaaFdgyHpeIUCS-3m3llsmRzp9xIOBR4lAI=@syst3mfailure.io
Fixes: 84c61fe1a75b ("tls: rx: do not use the standard strparser")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250807232907.600366-1-kuba@kernel.org
Change-Id: I3dff1f5e20d70f0090b516c260794d30250f66a3
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit eb0336f213fe88bbdb7d2b19c9c9ec19245a3155)
Signed-off-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/109902
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Kevin Berry <kpberry@google.com>
3 files changed