CVE-2026-53005: af_unix: Drop all SCM attributes for SOCKMAP.

CVE-2026-53005: af_unix: Drop all SCM attributes for SOCKMAP.

[Greg Kroah-Hartman]

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

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

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

af_unix: Drop all SCM attributes for SOCKMAP.

SOCKMAP can hide inflight fd from AF_UNIX GC.

When a socket in SOCKMAP receives skb with inflight fd,
sk_psock_verdict_data_ready() looks up the mapped socket and
enqueue skb to its psock->ingress_skb.

Since neither the old nor the new GC can inspect the psock
queue, the hidden skb leaks the inflight sockets.  Note that
this cannot be detected via kmemleak because inflight sockets
are linked to a global list.

In addition, SOCKMAP redirect breaks the Tarjan-based GC's
assumption that unix_edge.successor is always alive, which
is no longer true once skb is redirected, resulting in
use-after-free below. [0]

Moreover, SOCKMAP does not call scm_stat_del() properly,
so unix_show_fdinfo() could report an incorrect fd count.

sk_msg_recvmsg() does not support any SCM attributes in the
first place.

Let's drop all SCM attributes before passing skb to the
SOCKMAP layer.

[0]:
BUG: KASAN: slab-use-after-free in unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251)
Read of size 8 at addr ffff888125362670 by task kworker/56:1/496

CPU: 56 UID: 0 PID: 496 Comm: kworker/56:1 Not tainted 7.0.0-rc7-00263-gb9d8b856689d #3 PREEMPT(lazy)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
Workqueue: events sk_psock_backlog
Call Trace:
 <TASK>
 dump_stack_lvl (lib/dump_stack.c:122)
 print_report (mm/kasan/report.c:379)
 kasan_report (mm/kasan/report.c:597)
 unix_del_edges (net/unix/garbage.c:118 net/unix/garbage.c:181 net/unix/garbage.c:251)
 unix_destroy_fpl (net/unix/garbage.c:317)
 unix_destruct_scm (./include/net/scm.h:80 ./include/net/scm.h:86 net/unix/af_unix.c:1976)
 sk_psock_backlog (./include/linux/skbuff.h:?)
 process_scheduled_works (kernel/workqueue.c:?)
 worker_thread (kernel/workqueue.c:?)
 kthread (kernel/kthread.c:438)
 ret_from_fork (arch/x86/kernel/process.c:164)
 ret_from_fork_asm (arch/x86/entry/entry_64.S:258)
 </TASK>

Allocated by task 955:
 kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78)
 __kasan_slab_alloc (mm/kasan/common.c:369)
 kmem_cache_alloc_noprof (mm/slub.c:4539)
 sk_prot_alloc (net/core/sock.c:2240)
 sk_alloc (net/core/sock.c:2301)
 unix_create1 (net/unix/af_unix.c:1099)
 unix_create (net/unix/af_unix.c:1169)
 __sock_create (net/socket.c:1606)
 __sys_socketpair (net/socket.c:1811)
 __x64_sys_socketpair (net/socket.c:1863 net/socket.c:1860 net/socket.c:1860)
 do_syscall_64 (arch/x86/entry/syscall_64.c:?)
 entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)

Freed by task 496:
 kasan_save_track (mm/kasan/common.c:58 mm/kasan/common.c:78)
 kasan_save_free_info (mm/kasan/generic.c:587)
 __kasan_slab_free (mm/kasan/common.c:287)
 kmem_cache_free (mm/slub.c:6165)
 __sk_destruct (net/core/sock.c:2282 net/core/sock.c:2384)
 sk_psock_destroy (./include/net/sock.h:?)
 process_scheduled_works (kernel/workqueue.c:?)
 worker_thread (kernel/workqueue.c:?)
 kthread (kernel/kthread.c:438)
 ret_from_fork (arch/x86/kernel/process.c:164)
 ret_from_fork_asm (arch/x86/entry/entry_64.S:258)

The Linux kernel CVE team has assigned CVE-2026-53005 to this issue.


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

	Issue introduced in 5.15 with commit c63829182c37c2d6d0608976d15fa61ebebe9e6b and fixed in 7.0.10 with commit b34a1d83c74a124c968b5adb25c809db3e2eb86a
	Issue introduced in 5.15 with commit c63829182c37c2d6d0608976d15fa61ebebe9e6b and fixed in 7.1 with commit 965dc93481d1b80d341bdd16c27b16fe197175ee

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-2026-53005
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/unix/af_unix.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/b34a1d83c74a124c968b5adb25c809db3e2eb86a
	https://git.kernel.org/stable/c/965dc93481d1b80d341bdd16c27b16fe197175ee