CVE-2026-64436: net: af_key: initialize alg_key_len for IPComp states

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

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

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

net: af_key: initialize alg_key_len for IPComp states

pfkey_msg2xfrm_state() handles the IPComp (SADB_X_SATYPE_IPCOMP) case by
allocating x->calg and copying only the algorithm name:

	x->calg = kmalloc_obj(*x->calg);
	if (!x->calg) {
		err = -ENOMEM;
		goto out;
	}
	strcpy(x->calg->alg_name, a->name);
	x->props.calgo = sa->sadb_sa_encrypt;

Unlike the authentication (x->aalg) and encryption (x->ealg) branches of
the same function, the compression branch never initializes
calg->alg_key_len.  IPComp carries no key and the allocation only
reserves sizeof(struct xfrm_algo) (i.e. no room for a key), so the field
is left containing uninitialized slab data.

calg->alg_key_len is later used as a length by xfrm_algo_clone() when an
IPComp state is cloned during XFRM_MSG_MIGRATE:

	xfrm_state_migrate()
	  xfrm_state_clone_and_setup()
	    x->calg = xfrm_algo_clone(orig->calg);
	      kmemdup(orig, xfrm_alg_len(orig));

where xfrm_alg_len() returns sizeof(*alg) + (alg_key_len + 7) / 8.  With
a non-zero garbage alg_key_len, kmemdup() reads past the end of the
68-byte calg object.  Adding an IPComp SA via PF_KEY and then migrating
it triggers (net-next, KASAN, init_on_alloc=0):

  BUG: KASAN: slab-out-of-bounds in kmemdup_noprof+0x44/0x60
  Read of size 4164 at addr ff11000025a74980 by task diag2/9287
  CPU: 3 UID: 0 PID: 9287 Comm: diag2 7.1.0-rc6-g903db046d557 #1
  Call Trace:
   <TASK>
   dump_stack_lvl+0x10e/0x1f0
   print_report+0xf7/0x600
   kasan_report+0xe4/0x120
   kasan_check_range+0x105/0x1b0
   __asan_memcpy+0x23/0x60
   kmemdup_noprof+0x44/0x60
   xfrm_state_migrate+0x70a/0x1da0
   xfrm_migrate+0x753/0x18a0
   xfrm_do_migrate+0xb47/0xf10
   xfrm_user_rcv_msg+0x411/0xb50
   netlink_rcv_skb+0x158/0x420
   xfrm_netlink_rcv+0x71/0x90
   netlink_unicast+0x584/0x850
   netlink_sendmsg+0x8b0/0xdc0
   ____sys_sendmsg+0x9f7/0xb90
   ___sys_sendmsg+0x134/0x1d0
   __sys_sendmsg+0x16d/0x220
   do_syscall_64+0x116/0x7d0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   </TASK>

  Allocated by task 9287:
   kasan_save_stack+0x33/0x60
   kasan_save_track+0x14/0x30
   __kasan_kmalloc+0xaa/0xb0
   pfkey_add+0x2652/0x2ea0
   pfkey_process+0x6d0/0x830
   pfkey_sendmsg+0x42c/0x850
   __sys_sendto+0x461/0x4b0
   __x64_sys_sendto+0xe0/0x1c0
   do_syscall_64+0x116/0x7d0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f

  The buggy address belongs to the object at ff11000025a74980
   which belongs to the cache kmalloc-96 of size 96
  The buggy address is located 0 bytes inside of
   allocated 68-byte region [ff11000025a74980, ff11000025a749c4)

Depending on the uninitialized value the same field can instead request
an oversized kmemdup() allocation and make the migration clone fail.

The XFRM netlink path is not affected: verify_one_alg() rejects an
XFRMA_ALG_COMP attribute shorter than xfrm_alg_len(), so a calg added via
XFRM_MSG_NEWSA is always self-consistent.

Initialize calg->alg_key_len to 0, matching the aalg/ealg branches.

The Linux kernel CVE team has assigned CVE-2026-64436 to this issue.


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

	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 5.10.261 with commit 58e82fc3dedb57b1432292504415b224fd2d6acb
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 5.15.212 with commit 01b9115b55018123ef2449ac4951f89147a8428e
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 6.1.178 with commit 3f63d1752d90c0e28be931a48ab5d89bc97d637d
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 6.6.145 with commit 273c06b81d2e902b21acc801ae18c8276c8a9b69
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 6.12.96 with commit 6de2a650917bedaaefd65b17cede83c5e2c1dedd
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 6.18.39 with commit e8417353cbd078d10531ba3928e609c84ab09e6b
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 7.1.4 with commit cea34abc94b0a81e3a8b5cfb41cf45af37c2c67e
	Issue introduced in 2.6.21 with commit 80c9abaabf4283f7cf4a0b3597cd302506635b7f and fixed in 7.2-rc1 with commit d129c3177d7b1138fd5066fcc63a698b3ba415b0

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-2026-64436
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/key/af_key.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/58e82fc3dedb57b1432292504415b224fd2d6acb
	https://git.kernel.org/stable/c/01b9115b55018123ef2449ac4951f89147a8428e
	https://git.kernel.org/stable/c/3f63d1752d90c0e28be931a48ab5d89bc97d637d
	https://git.kernel.org/stable/c/273c06b81d2e902b21acc801ae18c8276c8a9b69
	https://git.kernel.org/stable/c/6de2a650917bedaaefd65b17cede83c5e2c1dedd
	https://git.kernel.org/stable/c/e8417353cbd078d10531ba3928e609c84ab09e6b
	https://git.kernel.org/stable/c/cea34abc94b0a81e3a8b5cfb41cf45af37c2c67e
	https://git.kernel.org/stable/c/d129c3177d7b1138fd5066fcc63a698b3ba415b0