CVE-2026-64046: net: tls: prevent chain-after-chain in plain text SG

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

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

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

net: tls: prevent chain-after-chain in plain text SG

Sashiko points out that if end = 0 (start != 0) the current
code will create a chain link to content type right after
the wrap link:

  This would create a chain where the wrap link points directly
  to another chain link. The scatterlist API sg_next iterator
  does not recursively resolve consecutive chain links.

meaning this is illegal input to crypto.

The wrapping link is unnecessary if end = 0. end is the entry after
the last one used so end = 0 means there's nothing pushed after
the wrap:

   end         start            i
    v            v              v
  [   ]...[   ][ d ][ d ][ d ][ d ][rsv for wrap]

Skip the wrapping in this case.

TLS 1.3 can use the "wrapping slot" for it's chaining if end = 0.
This avoids the chain-after-chain.

Move the wrap chaining before marking END and chaining off content
type, that feels like more logical ordering to me, but should not
matter from functional perspective.

The Linux kernel CVE team has assigned CVE-2026-64046 to this issue.


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

	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 5.10.258 with commit 49a5faaa471ddcd37b6893970c9916eb836e7c31
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 5.15.209 with commit 91359966e247c0244c66d50bbb8e74aefa4321c3
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 6.1.175 with commit 410351158dfef2d67fea6603680b3a6013c6ed9d
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 6.6.142 with commit acdc12b71c9aa4be5dcd2c8062753c6d2033e235
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 6.12.92 with commit 929b1548e63ac72e104c07d8ee8cbbeeba2fa89a
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 6.18.34 with commit af855f4c966afafef74faf8390c7b86568c0d46d
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 7.0.11 with commit b9c015ef1a7bf1e8dc67f21c6381f36deb2c3a36
	Issue introduced in 5.5 with commit 9aaaa56845a06aeabdd597cbe19492dc01f281ec and fixed in 7.1 with commit ff26a0e8377dec07e4a7230db7675bed1b9a6d03
	Issue introduced in 5.4.14 with commit d529d6c9f7e3aaeac13c4948f79799ccb825f29d

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-2026-64046
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/49a5faaa471ddcd37b6893970c9916eb836e7c31
	https://git.kernel.org/stable/c/91359966e247c0244c66d50bbb8e74aefa4321c3
	https://git.kernel.org/stable/c/410351158dfef2d67fea6603680b3a6013c6ed9d
	https://git.kernel.org/stable/c/acdc12b71c9aa4be5dcd2c8062753c6d2033e235
	https://git.kernel.org/stable/c/929b1548e63ac72e104c07d8ee8cbbeeba2fa89a
	https://git.kernel.org/stable/c/af855f4c966afafef74faf8390c7b86568c0d46d
	https://git.kernel.org/stable/c/b9c015ef1a7bf1e8dc67f21c6381f36deb2c3a36
	https://git.kernel.org/stable/c/ff26a0e8377dec07e4a7230db7675bed1b9a6d03