CVE-2026-74610: tls: don't leave a full plaintext sk_msg ring unpushed

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

tls: don't leave a full plaintext sk_msg ring unpushed

When the copy path in tls_sw_sendmsg_locked() adds the fragment that fills
the plaintext sk_msg ring, it does not set full_record, so the record is
left full and unpushed.  A later splice() then adds to an already full
ring: sk_msg_page_add() has no fullness check of its own, so sg.end wraps
onto sg.start and the ring appears empty.  Fragments added after that
overwrite live entries, and sg.size no longer matches what is reachable
between sg.start and sg.end, so pushing the record runs the scatterwalk off
the end of the scatterlist.

An unprivileged user can trigger this on a loopback TCP socket with the
"tls" ULP attached:

  BUG: kernel NULL pointer dereference, address: 0000000000000008
  RIP: 0010:memcpy_from_scatterwalk+0x32/0xc0
  Call Trace:
   skcipher_walk_next+0x1d1/0x2c0
   gcm_encrypt_aesni_avx+0x1e9/0x220
   bpf_exec_tx_verdict+0x3bb/0x860
   tls_sw_sendmsg+0xa1a/0xca0
   __sys_sendto+0x1da/0x1f0

Set full_record in the copy path when the ring becomes full, and push a
record that is already full on entry to the sendmsg loop.

The Linux kernel CVE team has assigned CVE-2026-74610 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.5 with commit fe1e81d4f73b6cbaed4fcc476960d26770642842 and fixed in 6.6.152 with commit aa8b14647721b5a4958712b35cf43e3125d47753
	Issue introduced in 6.5 with commit fe1e81d4f73b6cbaed4fcc476960d26770642842 and fixed in 6.12.104 with commit f634289a0b557a197c5f37284b623cefedfe73d5
	Issue introduced in 6.5 with commit fe1e81d4f73b6cbaed4fcc476960d26770642842 and fixed in 6.18.45 with commit 3fc5044796dd87b8d68be4207046f5ce2748174c
	Issue introduced in 6.5 with commit fe1e81d4f73b6cbaed4fcc476960d26770642842 and fixed in 7.1.9 with commit 3c5f8f2aa57c647b83add4896aab64aac5fdedad
	Issue introduced in 6.5 with commit fe1e81d4f73b6cbaed4fcc476960d26770642842 and fixed in 7.2 with commit 7bca91d63341274e857f4aeaad54d229405e93dc

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74610
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/tls/tls_sw.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/aa8b14647721b5a4958712b35cf43e3125d47753
	https://git.kernel.org/stable/c/f634289a0b557a197c5f37284b623cefedfe73d5
	https://git.kernel.org/stable/c/3fc5044796dd87b8d68be4207046f5ce2748174c
	https://git.kernel.org/stable/c/3c5f8f2aa57c647b83add4896aab64aac5fdedad
	https://git.kernel.org/stable/c/7bca91d63341274e857f4aeaad54d229405e93dc