linux-cve-announce - CVE-2025-40248: vsock: Ignore signal/timeout on connect() if already established

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Message-ID: <2025120430-CVE-2025-40248-506e@gregkh>
Date: Thu,  4 Dec 2025 16:57:29 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-40248: vsock: Ignore signal/timeout on connect() if already established

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

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

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

vsock: Ignore signal/timeout on connect() if already established

During connect(), acting on a signal/timeout by disconnecting an already
established socket leads to several issues:

1. connect() invoking vsock_transport_cancel_pkt() ->
   virtio_transport_purge_skbs() may race with sendmsg() invoking
   virtio_transport_get_credit(). This results in a permanently elevated
   `vvs->bytes_unsent`. Which, in turn, confuses the SOCK_LINGER handling.

2. connect() resetting a connected socket's state may race with socket
   being placed in a sockmap. A disconnected socket remaining in a sockmap
   breaks sockmap's assumptions. And gives rise to WARNs.

3. connect() transitioning SS_CONNECTED -> SS_UNCONNECTED allows for a
   transport change/drop after TCP_ESTABLISHED. Which poses a problem for
   any simultaneous sendmsg() or connect() and may result in a
   use-after-free/null-ptr-deref.

Do not disconnect socket on signal/timeout. Keep the logic for unconnected
sockets: they don't linger, can't be placed in a sockmap, are rejected by
sendmsg().

[1]: https://lore.kernel.org/netdev/e07fd95c-9a38-4eea-9638-133e38c2ec9b@rbox.co/
[2]: https://lore.kernel.org/netdev/20250317-vsock-trans-signal-race-v4-0-fc8837f3f1d4@rbox.co/
[3]: https://lore.kernel.org/netdev/60f1b7db-3099-4f6a-875e-af9f6ef194f6@rbox.co/

The Linux kernel CVE team has assigned CVE-2025-40248 to this issue.

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

	Issue introduced in 3.9 with commit d021c344051af91f42c5ba9fdedc176740cbd238 and fixed in 5.4.302 with commit 3f71753935d648082a8279a97d30efe6b85be680
	Issue introduced in 3.9 with commit d021c344051af91f42c5ba9fdedc176740cbd238 and fixed in 6.6.118 with commit 5998da5a8208ae9ad7838ba322bccb2bdcd95e81
	Issue introduced in 3.9 with commit d021c344051af91f42c5ba9fdedc176740cbd238 and fixed in 6.12.60 with commit f1c170cae285e4b8f61be043bb17addc3d0a14b5
	Issue introduced in 3.9 with commit d021c344051af91f42c5ba9fdedc176740cbd238 and fixed in 6.17.10 with commit ab6b19f690d89ae4709fba73a3c4a7911f495b7a
	Issue introduced in 3.9 with commit d021c344051af91f42c5ba9fdedc176740cbd238 and fixed in 6.18 with commit 002541ef650b742a198e4be363881439bb9d86b4

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-2025-40248
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/3f71753935d648082a8279a97d30efe6b85be680
	https://git.kernel.org/stable/c/5998da5a8208ae9ad7838ba322bccb2bdcd95e81
	https://git.kernel.org/stable/c/f1c170cae285e4b8f61be043bb17addc3d0a14b5
	https://git.kernel.org/stable/c/ab6b19f690d89ae4709fba73a3c4a7911f495b7a
	https://git.kernel.org/stable/c/002541ef650b742a198e4be363881439bb9d86b4