Message-ID: <2025070422-CVE-2025-38211-215a@gregkh>
Date: Fri,  4 Jul 2025 15:37:40 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38211: RDMA/iwcm: Fix use-after-free of work objects after cm_id destruction

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

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

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

RDMA/iwcm: Fix use-after-free of work objects after cm_id destruction

The commit 59c68ac31e15 ("iw_cm: free cm_id resources on the last
deref") simplified cm_id resource management by freeing cm_id once all
references to the cm_id were removed. The references are removed either
upon completion of iw_cm event handlers or when the application destroys
the cm_id. This commit introduced the use-after-free condition where
cm_id_private object could still be in use by event handler works during
the destruction of cm_id. The commit aee2424246f9 ("RDMA/iwcm: Fix a
use-after-free related to destroying CM IDs") addressed this use-after-
free by flushing all pending works at the cm_id destruction.

However, still another use-after-free possibility remained. It happens
with the work objects allocated for each cm_id_priv within
alloc_work_entries() during cm_id creation, and subsequently freed in
dealloc_work_entries() once all references to the cm_id are removed.
If the cm_id's last reference is decremented in the event handler work,
the work object for the work itself gets removed, and causes the use-
after-free BUG below:

  BUG: KASAN: slab-use-after-free in __pwq_activate_work+0x1ff/0x250
  Read of size 8 at addr ffff88811f9cf800 by task kworker/u16:1/147091

  CPU: 2 UID: 0 PID: 147091 Comm: kworker/u16:1 Not tainted 6.15.0-rc2+ #27 PREEMPT(voluntary)
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014
  Workqueue:  0x0 (iw_cm_wq)
  Call Trace:
   <TASK>
   dump_stack_lvl+0x6a/0x90
   print_report+0x174/0x554
   ? __virt_addr_valid+0x208/0x430
   ? __pwq_activate_work+0x1ff/0x250
   kasan_report+0xae/0x170
   ? __pwq_activate_work+0x1ff/0x250
   __pwq_activate_work+0x1ff/0x250
   pwq_dec_nr_in_flight+0x8c5/0xfb0
   process_one_work+0xc11/0x1460
   ? __pfx_process_one_work+0x10/0x10
   ? assign_work+0x16c/0x240
   worker_thread+0x5ef/0xfd0
   ? __pfx_worker_thread+0x10/0x10
   kthread+0x3b0/0x770
   ? __pfx_kthread+0x10/0x10
   ? rcu_is_watching+0x11/0xb0
   ? _raw_spin_unlock_irq+0x24/0x50
   ? rcu_is_watching+0x11/0xb0
   ? __pfx_kthread+0x10/0x10
   ret_from_fork+0x30/0x70
   ? __pfx_kthread+0x10/0x10
   ret_from_fork_asm+0x1a/0x30
   </TASK>

  Allocated by task 147416:
   kasan_save_stack+0x2c/0x50
   kasan_save_track+0x10/0x30
   __kasan_kmalloc+0xa6/0xb0
   alloc_work_entries+0xa9/0x260 [iw_cm]
   iw_cm_connect+0x23/0x4a0 [iw_cm]
   rdma_connect_locked+0xbfd/0x1920 [rdma_cm]
   nvme_rdma_cm_handler+0x8e5/0x1b60 [nvme_rdma]
   cma_cm_event_handler+0xae/0x320 [rdma_cm]
   cma_work_handler+0x106/0x1b0 [rdma_cm]
   process_one_work+0x84f/0x1460
   worker_thread+0x5ef/0xfd0
   kthread+0x3b0/0x770
   ret_from_fork+0x30/0x70
   ret_from_fork_asm+0x1a/0x30

  Freed by task 147091:
   kasan_save_stack+0x2c/0x50
   kasan_save_track+0x10/0x30
   kasan_save_free_info+0x37/0x60
   __kasan_slab_free+0x4b/0x70
   kfree+0x13a/0x4b0
   dealloc_work_entries+0x125/0x1f0 [iw_cm]
   iwcm_deref_id+0x6f/0xa0 [iw_cm]
   cm_work_handler+0x136/0x1ba0 [iw_cm]
   process_one_work+0x84f/0x1460
   worker_thread+0x5ef/0xfd0
   kthread+0x3b0/0x770
   ret_from_fork+0x30/0x70
   ret_from_fork_asm+0x1a/0x30

  Last potentially related work creation:
   kasan_save_stack+0x2c/0x50
   kasan_record_aux_stack+0xa3/0xb0
   __queue_work+0x2ff/0x1390
   queue_work_on+0x67/0xc0
   cm_event_handler+0x46a/0x820 [iw_cm]
   siw_cm_upcall+0x330/0x650 [siw]
   siw_cm_work_handler+0x6b9/0x2b20 [siw]
   process_one_work+0x84f/0x1460
   worker_thread+0x5ef/0xfd0
   kthread+0x3b0/0x770
   ret_from_fork+0x30/0x70
   ret_from_fork_asm+0x1a/0x30

This BUG is reproducible by repeating the blktests test case nvme/061
for the rdma transport and the siw driver.

To avoid the use-after-free of cm_id_private work objects, ensure that
the last reference to the cm_id is decremented not in the event handler
works, but in the cm_id destruction context. For that purpose, move
iwcm_deref_id() call from destroy_cm_id() to the callers of
destroy_cm_id(). In iw_destroy_cm_id(), call iwcm_deref_id() after
flushing the pending works.

During the fix work, I noticed that iw_destroy_cm_id() is called from
cm_work_handler() and process_event() context. However, the comment of
iw_destroy_cm_id() notes that the function "cannot be called by the
event thread". Drop the false comment.

The Linux kernel CVE team has assigned CVE-2025-38211 to this issue.


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

	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 5.15.186 with commit 3b4a50d733acad6831f6bd9288a76a80f70650ac
	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 6.1.142 with commit 78381dc8a6b61c9bb9987d37b4d671b99767c4a1
	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 6.6.95 with commit 23a707bbcbea468eedb398832eeb7e8e0ceafd21
	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 6.12.35 with commit 764c9f69beabef8bdc651a7746c59f7a340d104f
	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 6.15.4 with commit fd960b5ddf4faf00da43babdd3acda68842e1f6a
	Issue introduced in 4.8 with commit 59c68ac31e15ad09d2cb04734e3c8c544a95f8d4 and fixed in 6.16-rc1 with commit 6883b680e703c6b2efddb4e7a8d891ce1803d06b

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-2025-38211
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:
	drivers/infiniband/core/iwcm.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/3b4a50d733acad6831f6bd9288a76a80f70650ac
	https://git.kernel.org/stable/c/78381dc8a6b61c9bb9987d37b4d671b99767c4a1
	https://git.kernel.org/stable/c/23a707bbcbea468eedb398832eeb7e8e0ceafd21
	https://git.kernel.org/stable/c/764c9f69beabef8bdc651a7746c59f7a340d104f
	https://git.kernel.org/stable/c/fd960b5ddf4faf00da43babdd3acda68842e1f6a
	https://git.kernel.org/stable/c/6883b680e703c6b2efddb4e7a8d891ce1803d06b

Powered by blists - more mailing lists