linux-cve-announce - CVE-2024-50253: bpf: Check the validity of nr_words in bpf_iter_bits

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Message-ID: <2024110937-CVE-2024-50253-7a6b@gregkh>
Date: Sat,  9 Nov 2024 11:16:01 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-50253: bpf: Check the validity of nr_words in bpf_iter_bits_new()

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

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

bpf: Check the validity of nr_words in bpf_iter_bits_new()

Check the validity of nr_words in bpf_iter_bits_new(). Without this
check, when multiplication overflow occurs for nr_bits (e.g., when
nr_words = 0x0400-0001, nr_bits becomes 64), stack corruption may occur
due to bpf_probe_read_kernel_common(..., nr_bytes = 0x2000-0008).

Fix it by limiting the maximum value of nr_words to 511. The value is
derived from the current implementation of BPF memory allocator. To
ensure compatibility if the BPF memory allocator's size limitation
changes in the future, use the helper bpf_mem_alloc_check_size() to
check whether nr_bytes is too larger. And return -E2BIG instead of
-ENOMEM for oversized nr_bytes.

The Linux kernel CVE team has assigned CVE-2024-50253 to this issue.


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

	Issue introduced in 6.11 with commit 4665415975b0 and fixed in 6.11.7 with commit c9539e09c678
	Issue introduced in 6.11 with commit 4665415975b0 and fixed in 6.12-rc6 with commit 393397fbdcad

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-2024-50253
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:
	kernel/bpf/helpers.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/c9539e09c67880ecd88b51188c346a2cc078b06c
	https://git.kernel.org/stable/c/393397fbdcad7396639d7077c33f86169184ba99