linux-cve-announce - CVE-2025-38528: bpf: Reject %p% format string in bprintf-like helpers

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Message-ID: <2025081654-CVE-2025-38528-153c@gregkh>
Date: Sat, 16 Aug 2025 13:13:59 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38528: bpf: Reject %p% format string in bprintf-like helpers

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

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

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

bpf: Reject %p% format string in bprintf-like helpers

static const char fmt[] = "%p%";
    bpf_trace_printk(fmt, sizeof(fmt));

The above BPF program isn't rejected and causes a kernel warning at
runtime:

    Please remove unsupported %\x00 in format string
    WARNING: CPU: 1 PID: 7244 at lib/vsprintf.c:2680 format_decode+0x49c/0x5d0

This happens because bpf_bprintf_prepare skips over the second %,
detected as punctuation, while processing %p. This patch fixes it by
not skipping over punctuation. %\x00 is then processed in the next
iteration and rejected.

The Linux kernel CVE team has assigned CVE-2025-38528 to this issue.


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

	Issue introduced in 5.13 with commit 48cac3f4a96ddf08df8e53809ed066de0dc93915 and fixed in 6.1.147 with commit 61d5fa45ed13e42af14c7e959baba9908b8ee6d4
	Issue introduced in 5.13 with commit 48cac3f4a96ddf08df8e53809ed066de0dc93915 and fixed in 6.6.100 with commit e7be679124bae8cf4fa6e40d7e1661baddfb3289
	Issue introduced in 5.13 with commit 48cac3f4a96ddf08df8e53809ed066de0dc93915 and fixed in 6.12.40 with commit 6952aeace93f8c9ea01849efecac24dd3152c9c9
	Issue introduced in 5.13 with commit 48cac3f4a96ddf08df8e53809ed066de0dc93915 and fixed in 6.15.8 with commit 1c5f5fd47bbda17cb885fe6f03730702cd53d3f8
	Issue introduced in 5.13 with commit 48cac3f4a96ddf08df8e53809ed066de0dc93915 and fixed in 6.16 with commit f8242745871f81a3ac37f9f51853d12854fd0b58

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-2025-38528
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/61d5fa45ed13e42af14c7e959baba9908b8ee6d4
	https://git.kernel.org/stable/c/e7be679124bae8cf4fa6e40d7e1661baddfb3289
	https://git.kernel.org/stable/c/6952aeace93f8c9ea01849efecac24dd3152c9c9
	https://git.kernel.org/stable/c/1c5f5fd47bbda17cb885fe6f03730702cd53d3f8
	https://git.kernel.org/stable/c/f8242745871f81a3ac37f9f51853d12854fd0b58