linux-cve-announce - CVE-2023-53272: net: ena: fix shift-out-of-bounds in exponential backoff

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Message-ID: <2025091604-CVE-2023-53272-3be5@gregkh>
Date: Tue, 16 Sep 2025 10:07:10 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2023-53272: net: ena: fix shift-out-of-bounds in exponential backoff

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

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

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

net: ena: fix shift-out-of-bounds in exponential backoff

The ENA adapters on our instances occasionally reset.  Once recently
logged a UBSAN failure to console in the process:

  UBSAN: shift-out-of-bounds in build/linux/drivers/net/ethernet/amazon/ena/ena_com.c:540:13
  shift exponent 32 is too large for 32-bit type 'unsigned int'
  CPU: 28 PID: 70012 Comm: kworker/u72:2 Kdump: loaded not tainted 5.15.117
  Hardware name: Amazon EC2 c5d.9xlarge/, BIOS 1.0 10/16/2017
  Workqueue: ena ena_fw_reset_device [ena]
  Call Trace:
  <TASK>
  dump_stack_lvl+0x4a/0x63
  dump_stack+0x10/0x16
  ubsan_epilogue+0x9/0x36
  __ubsan_handle_shift_out_of_bounds.cold+0x61/0x10e
  ? __const_udelay+0x43/0x50
  ena_delay_exponential_backoff_us.cold+0x16/0x1e [ena]
  wait_for_reset_state+0x54/0xa0 [ena]
  ena_com_dev_reset+0xc8/0x110 [ena]
  ena_down+0x3fe/0x480 [ena]
  ena_destroy_device+0xeb/0xf0 [ena]
  ena_fw_reset_device+0x30/0x50 [ena]
  process_one_work+0x22b/0x3d0
  worker_thread+0x4d/0x3f0
  ? process_one_work+0x3d0/0x3d0
  kthread+0x12a/0x150
  ? set_kthread_struct+0x50/0x50
  ret_from_fork+0x22/0x30
  </TASK>

Apparently, the reset delays are getting so large they can trigger a
UBSAN panic.

Looking at the code, the current timeout is capped at 5000us.  Using a
base value of 100us, the current code will overflow after (1<<29).  Even
at values before 32, this function wraps around, perhaps
unintentionally.

Cap the value of the exponent used for this backoff at (1<<16) which is
larger than currently necessary, but large enough to support bigger
values in the future.

The Linux kernel CVE team has assigned CVE-2023-53272 to this issue.

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

	Issue introduced in 5.8 with commit 4bb7f4cf60e38a00965d22aa5979ab143193d41f and fixed in 5.10.188 with commit 1e760b2d18bf129b3da052c2946c02758e97d15e
	Issue introduced in 5.8 with commit 4bb7f4cf60e38a00965d22aa5979ab143193d41f and fixed in 5.15.121 with commit 3e36cc94d6e60a27f27498adf1c71eeba769ab33
	Issue introduced in 5.8 with commit 4bb7f4cf60e38a00965d22aa5979ab143193d41f and fixed in 6.1.40 with commit 90947ebf8794e3c229fb2e16e37f1bfea6877f14
	Issue introduced in 5.8 with commit 4bb7f4cf60e38a00965d22aa5979ab143193d41f and fixed in 6.4.5 with commit 0939c264729d4a081ff88efce2ffdf85dc5331e0
	Issue introduced in 5.8 with commit 4bb7f4cf60e38a00965d22aa5979ab143193d41f and fixed in 6.5 with commit 1e9cb763e9bacf0c932aa948f50dcfca6f519a26

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-2023-53272
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/amazon/ena/ena_com.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/1e760b2d18bf129b3da052c2946c02758e97d15e
	https://git.kernel.org/stable/c/3e36cc94d6e60a27f27498adf1c71eeba769ab33
	https://git.kernel.org/stable/c/90947ebf8794e3c229fb2e16e37f1bfea6877f14
	https://git.kernel.org/stable/c/0939c264729d4a081ff88efce2ffdf85dc5331e0
	https://git.kernel.org/stable/c/1e9cb763e9bacf0c932aa948f50dcfca6f519a26