Message-ID: <2025072501-CVE-2025-38440-cb71@gregkh>
Date: Fri, 25 Jul 2025 17:28:02 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38440: net/mlx5e: Fix race between DIM disable and net_dim()

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

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

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

net/mlx5e: Fix race between DIM disable and net_dim()

There's a race between disabling DIM and NAPI callbacks using the dim
pointer on the RQ or SQ.

If NAPI checks the DIM state bit and sees it still set, it assumes
`rq->dim` or `sq->dim` is valid. But if DIM gets disabled right after
that check, the pointer might already be set to NULL, leading to a NULL
pointer dereference in net_dim().

Fix this by calling `synchronize_net()` before freeing the DIM context.
This ensures all in-progress NAPI callbacks are finished before the
pointer is cleared.

Kernel log:

BUG: kernel NULL pointer dereference, address: 0000000000000000
...
RIP: 0010:net_dim+0x23/0x190
...
Call Trace:
 <TASK>
 ? __die+0x20/0x60
 ? page_fault_oops+0x150/0x3e0
 ? common_interrupt+0xf/0xa0
 ? sysvec_call_function_single+0xb/0x90
 ? exc_page_fault+0x74/0x130
 ? asm_exc_page_fault+0x22/0x30
 ? net_dim+0x23/0x190
 ? mlx5e_poll_ico_cq+0x41/0x6f0 [mlx5_core]
 ? sysvec_apic_timer_interrupt+0xb/0x90
 mlx5e_handle_rx_dim+0x92/0xd0 [mlx5_core]
 mlx5e_napi_poll+0x2cd/0xac0 [mlx5_core]
 ? mlx5e_poll_ico_cq+0xe5/0x6f0 [mlx5_core]
 busy_poll_stop+0xa2/0x200
 ? mlx5e_napi_poll+0x1d9/0xac0 [mlx5_core]
 ? mlx5e_trigger_irq+0x130/0x130 [mlx5_core]
 __napi_busy_loop+0x345/0x3b0
 ? sysvec_call_function_single+0xb/0x90
 ? asm_sysvec_call_function_single+0x16/0x20
 ? sysvec_apic_timer_interrupt+0xb/0x90
 ? pcpu_free_area+0x1e4/0x2e0
 napi_busy_loop+0x11/0x20
 xsk_recvmsg+0x10c/0x130
 sock_recvmsg+0x44/0x70
 __sys_recvfrom+0xbc/0x130
 ? __schedule+0x398/0x890
 __x64_sys_recvfrom+0x20/0x30
 do_syscall_64+0x4c/0x100
 entry_SYSCALL_64_after_hwframe+0x4b/0x53
...
---[ end trace 0000000000000000 ]---
...
---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---

The Linux kernel CVE team has assigned CVE-2025-38440 to this issue.


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

	Issue introduced in 6.10 with commit 445a25f6e1a2f6a132b06af6ede4f3c9b5f9af68 and fixed in 6.12.39 with commit 7581afc051542e11ccf3ade68acd01b7fb1a3cde
	Issue introduced in 6.10 with commit 445a25f6e1a2f6a132b06af6ede4f3c9b5f9af68 and fixed in 6.15.7 with commit 2bc6fb90486e42dd80e660ef7a40c02b2516c6d6
	Issue introduced in 6.10 with commit 445a25f6e1a2f6a132b06af6ede4f3c9b5f9af68 and fixed in 6.16-rc6 with commit eb41a264a3a576dc040ee37c3d9d6b7e2d9be968

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-2025-38440
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/net/ethernet/mellanox/mlx5/core/en_dim.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/7581afc051542e11ccf3ade68acd01b7fb1a3cde
	https://git.kernel.org/stable/c/2bc6fb90486e42dd80e660ef7a40c02b2516c6d6
	https://git.kernel.org/stable/c/eb41a264a3a576dc040ee37c3d9d6b7e2d9be968

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