CVE-2026-72252: netfilter: nft_set_pipapo: don't leak bad clone into future transaction

CVE-2026-72252: netfilter: nft_set_pipapo: don't leak bad clone into future transaction

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

netfilter: nft_set_pipapo: don't leak bad clone into future transaction

On memory allocation failure the cloned nft_pipapo_match can enter a bad
state:
 - some fields can have their lookup tables resized while others did
   not
 - bits might have been toggled
 - scratch map can be undersized which also means m->bsize_max can be
   lower than what is required

This means that the next insertion in the same batch can trigger
out-of-bounds writes.

Furthermore, a failure in the first can result in the bad clone to
leak into the next transaction because the abort callback is never
executed in this case (the upper layer saw an error and no attempt to
allocate a transactional request was made).

Record a state for the nft_pipapo_match structure:
- NEW (pristine clone)
- MOD (modified clone with good state)
- ERR (potentially bogus content)

Then make it so that deletes and insertions fail when the clone
entered ERR state.

In case the very first insert attempt results in an error, free the
clone right away.

The Linux kernel CVE team has assigned CVE-2026-72252 to this issue.


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

	Issue introduced in 5.6 with commit 3c4287f62044a90e73a561aa05fc46e62da173da and fixed in 6.6.148 with commit 047e813324eac2ac60cddfb58bcdbd0144eadb09
	Issue introduced in 5.6 with commit 3c4287f62044a90e73a561aa05fc46e62da173da and fixed in 6.12.97 with commit 610e3b73efaec3dd81a95dcda2421ad7d9795bd0
	Issue introduced in 5.6 with commit 3c4287f62044a90e73a561aa05fc46e62da173da and fixed in 6.18.40 with commit 02b6b0e892aea582590671796fd6eff5b93ea93f
	Issue introduced in 5.6 with commit 3c4287f62044a90e73a561aa05fc46e62da173da and fixed in 7.1.5 with commit e74f9680e1b64872a51cc7b5bda1edaaa08aa51f
	Issue introduced in 5.6 with commit 3c4287f62044a90e73a561aa05fc46e62da173da and fixed in 7.2-rc2 with commit 47e65eff50691f0a5b79d325e28d83ec1da43bcf

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-2026-72252
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/netfilter/nft_set_pipapo.c
	net/netfilter/nft_set_pipapo.h


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/047e813324eac2ac60cddfb58bcdbd0144eadb09
	https://git.kernel.org/stable/c/610e3b73efaec3dd81a95dcda2421ad7d9795bd0
	https://git.kernel.org/stable/c/02b6b0e892aea582590671796fd6eff5b93ea93f
	https://git.kernel.org/stable/c/e74f9680e1b64872a51cc7b5bda1edaaa08aa51f
	https://git.kernel.org/stable/c/47e65eff50691f0a5b79d325e28d83ec1da43bcf