linux-cve-announce - CVE-2025-21886: RDMA/mlx5: Fix implicit ODP hang on parent deregistration

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Message-ID: <2025032713-CVE-2025-21886-9ca3@gregkh>
Date: Thu, 27 Mar 2025 15:58:20 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21886: RDMA/mlx5: Fix implicit ODP hang on parent deregistration

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

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

RDMA/mlx5: Fix implicit ODP hang on parent deregistration

Fix the destroy_unused_implicit_child_mr() to prevent hanging during
parent deregistration as of below [1].

Upon entering destroy_unused_implicit_child_mr(), the reference count
for the implicit MR parent is incremented using:
refcount_inc_not_zero().

A corresponding decrement must be performed if
free_implicit_child_mr_work() is not called.

The code has been updated to properly manage the reference count that
was incremented.

[1]
INFO: task python3:2157 blocked for more than 120 seconds.
Not tainted 6.12.0-rc7+ #1633
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:python3         state:D stack:0     pid:2157 tgid:2157  ppid:1685   flags:0x00000000
Call Trace:
<TASK>
__schedule+0x420/0xd30
schedule+0x47/0x130
__mlx5_ib_dereg_mr+0x379/0x5d0 [mlx5_ib]
? __pfx_autoremove_wake_function+0x10/0x10
ib_dereg_mr_user+0x5f/0x120 [ib_core]
? lock_release+0xc6/0x280
destroy_hw_idr_uobject+0x1d/0x60 [ib_uverbs]
uverbs_destroy_uobject+0x58/0x1d0 [ib_uverbs]
uobj_destroy+0x3f/0x70 [ib_uverbs]
ib_uverbs_cmd_verbs+0x3e4/0xbb0 [ib_uverbs]
? __pfx_uverbs_destroy_def_handler+0x10/0x10 [ib_uverbs]
? lock_acquire+0xc1/0x2f0
? ib_uverbs_ioctl+0xcb/0x170 [ib_uverbs]
? ib_uverbs_ioctl+0x116/0x170 [ib_uverbs]
? lock_release+0xc6/0x280
ib_uverbs_ioctl+0xe7/0x170 [ib_uverbs]
? ib_uverbs_ioctl+0xcb/0x170 [ib_uverbs]
 __x64_sys_ioctl+0x1b0/0xa70
? kmem_cache_free+0x221/0x400
do_syscall_64+0x6b/0x140
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f20f21f017b
RSP: 002b:00007ffcfc4a77c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffcfc4a78d8 RCX: 00007f20f21f017b
RDX: 00007ffcfc4a78c0 RSI: 00000000c0181b01 RDI: 0000000000000003
RBP: 00007ffcfc4a78a0 R08: 000056147d125190 R09: 00007f20f1f14c60
R10: 0000000000000001 R11: 0000000000000246 R12: 00007ffcfc4a7890
R13: 000000000000001c R14: 000056147d100fc0 R15: 00007f20e365c9d0
</TASK>

The Linux kernel CVE team has assigned CVE-2025-21886 to this issue.


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

	Issue introduced in 6.12.13 with commit 7cc8f681f6d4ae4478ae0f60485fc768f2b450da and fixed in 6.12.18 with commit cb96ae783e7249e8e5a50c22952c0bb2983133df
	Issue introduced in 6.13.2 with commit edfb65dbb9ffd3102f3ff4dd21316158e56f1976 and fixed in 6.13.6 with commit a095ede2daca49d15e74d66d014883f2fa8bb924

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-2025-21886
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/hw/mlx5/odp.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/cb96ae783e7249e8e5a50c22952c0bb2983133df
	https://git.kernel.org/stable/c/a095ede2daca49d15e74d66d014883f2fa8bb924
	https://git.kernel.org/stable/c/3d8c6f26893d55fab218ad086719de1fc9bb86ba