CVE-2025-21755: vsock: Orphan socket after transport release

CVE-2025-21755: vsock: Orphan socket after transport release

[Greg Kroah-Hartman]

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

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

vsock: Orphan socket after transport release

During socket release, sock_orphan() is called without considering that it
sets sk->sk_wq to NULL. Later, if SO_LINGER is enabled, this leads to a
null pointer dereferenced in virtio_transport_wait_close().

Orphan the socket only after transport release.

Partially reverts the 'Fixes:' commit.

KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
 lock_acquire+0x19e/0x500
 _raw_spin_lock_irqsave+0x47/0x70
 add_wait_queue+0x46/0x230
 virtio_transport_release+0x4e7/0x7f0
 __vsock_release+0xfd/0x490
 vsock_release+0x90/0x120
 __sock_release+0xa3/0x250
 sock_close+0x14/0x20
 __fput+0x35e/0xa90
 __x64_sys_close+0x78/0xd0
 do_syscall_64+0x93/0x1b0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

The Linux kernel CVE team has assigned CVE-2025-21755 to this issue.


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

	Issue introduced in 6.14-rc1 with commit fcdd2242c0231032fc84e1404315c245ae56322a and fixed in 6.14-rc3 with commit 78dafe1cf3afa02ed71084b350713b07e72a18fb

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-2025-21755
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/vmw_vsock/af_vsock.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/f3b8e9d3414b2eb083d8293be25a949fe480897b
	https://git.kernel.org/stable/c/3a866f8376f0a5c848dcb59cd26df845fffbe6d8
	https://git.kernel.org/stable/c/94d81870eec7ad2dd7af80bffd314ded26caea1a
	https://git.kernel.org/stable/c/78dafe1cf3afa02ed71084b350713b07e72a18fb