linux-cve-announce - CVE-2025-38339: powerpc/bpf: fix JIT code size calculation of bpf trampoline

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Message-ID: <2025071034-CVE-2025-38339-90f8@gregkh>
Date: Thu, 10 Jul 2025 10:15:47 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-38339: powerpc/bpf: fix JIT code size calculation of bpf trampoline

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

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

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

powerpc/bpf: fix JIT code size calculation of bpf trampoline

arch_bpf_trampoline_size() provides JIT size of the BPF trampoline
before the buffer for JIT'ing it is allocated. The total number of
instructions emitted for BPF trampoline JIT code depends on where
the final image is located. So, the size arrived at with the dummy
pass in arch_bpf_trampoline_size() can vary from the actual size
needed in  arch_prepare_bpf_trampoline().  When the instructions
accounted in  arch_bpf_trampoline_size() is less than the number of
instructions emitted during the actual JIT compile of the trampoline,
the below warning is produced:

  WARNING: CPU: 8 PID: 204190 at arch/powerpc/net/bpf_jit_comp.c:981 __arch_prepare_bpf_trampoline.isra.0+0xd2c/0xdcc

which is:

  /* Make sure the trampoline generation logic doesn't overflow */
  if (image && WARN_ON_ONCE(&image[ctx->idx] >
  			(u32 *)rw_image_end - BPF_INSN_SAFETY)) {

So, during the dummy pass, instead of providing some arbitrary image
location, account for maximum possible instructions if and when there
is a dependency with image location for JIT'ing.

The Linux kernel CVE team has assigned CVE-2025-38339 to this issue.

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

	Issue introduced in 6.13 with commit d243b62b7bd3d5314382d3b54e4992226245e936 and fixed in 6.15.4 with commit 7833deb95e05bec146414b3a2feb24f025ca27c0
	Issue introduced in 6.13 with commit d243b62b7bd3d5314382d3b54e4992226245e936 and fixed in 6.16-rc1 with commit 59ba025948be2a92e8bc9ae1cbdaf197660bd508

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-2025-38339
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:
	arch/powerpc/net/bpf_jit.h
	arch/powerpc/net/bpf_jit_comp.c
	arch/powerpc/net/bpf_jit_comp32.c
	arch/powerpc/net/bpf_jit_comp64.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/7833deb95e05bec146414b3a2feb24f025ca27c0
	https://git.kernel.org/stable/c/59ba025948be2a92e8bc9ae1cbdaf197660bd508