linux-cve-announce - CVE-2025-38544: rxrpc: Fix bug due to prealloc collision

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Message-ID: <2025081627-CVE-2025-38544-a2ab@gregkh>
Date: Sat, 16 Aug 2025 13:22:30 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38544: rxrpc: Fix bug due to prealloc collision

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

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

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

rxrpc: Fix bug due to prealloc collision

When userspace is using AF_RXRPC to provide a server, it has to preallocate
incoming calls and assign to them call IDs that will be used to thread
related recvmsg() and sendmsg() together.  The preallocated call IDs will
automatically be attached to calls as they come in until the pool is empty.

To the kernel, the call IDs are just arbitrary numbers, but userspace can
use the call ID to hold a pointer to prepared structs.  In any case, the
user isn't permitted to create two calls with the same call ID (call IDs
become available again when the call ends) and EBADSLT should result from
sendmsg() if an attempt is made to preallocate a call with an in-use call
ID.

However, the cleanup in the error handling will trigger both assertions in
rxrpc_cleanup_call() because the call isn't marked complete and isn't
marked as having been released.

Fix this by setting the call state in rxrpc_service_prealloc_one() and then
marking it as being released before calling the cleanup function.

The Linux kernel CVE team has assigned CVE-2025-38544 to this issue.

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

	Issue introduced in 4.9 with commit 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 and fixed in 6.6.99 with commit 432c5363cd6fe5a928bbc94524d28b05515684dd
	Issue introduced in 4.9 with commit 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 and fixed in 6.12.39 with commit 5385ad53793de2ab11e396bdcdaa65bb04b4dad6
	Issue introduced in 4.9 with commit 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 and fixed in 6.15.7 with commit d8ffb47a443919277cb093c3db1ec6c0a06880b1
	Issue introduced in 4.9 with commit 00e907127e6f86d0f9b122d9b4347a8aa09a8b61 and fixed in 6.16 with commit 69e4186773c6445b258fb45b6e1df18df831ec45

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-2025-38544
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/rxrpc/call_accept.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/432c5363cd6fe5a928bbc94524d28b05515684dd
	https://git.kernel.org/stable/c/5385ad53793de2ab11e396bdcdaa65bb04b4dad6
	https://git.kernel.org/stable/c/d8ffb47a443919277cb093c3db1ec6c0a06880b1
	https://git.kernel.org/stable/c/69e4186773c6445b258fb45b6e1df18df831ec45