linux-cve-announce - CVE-2025-39917: bpf: Fix out-of-bounds dynptr write in bpf_crypto

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Message-ID: <2025100112-CVE-2025-39917-b3a9@gregkh>
Date: Wed,  1 Oct 2025 09:47:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-39917: bpf: Fix out-of-bounds dynptr write in bpf_crypto_crypt

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

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

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

bpf: Fix out-of-bounds dynptr write in bpf_crypto_crypt

Stanislav reported that in bpf_crypto_crypt() the destination dynptr's
size is not validated to be at least as large as the source dynptr's
size before calling into the crypto backend with 'len = src_len'. This
can result in an OOB write when the destination is smaller than the
source.

Concretely, in mentioned function, psrc and pdst are both linear
buffers fetched from each dynptr:

  psrc = __bpf_dynptr_data(src, src_len);
  [...]
  pdst = __bpf_dynptr_data_rw(dst, dst_len);
  [...]
  err = decrypt ?
        ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv) :
        ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv);

The crypto backend expects pdst to be large enough with a src_len length
that can be written. Add an additional src_len > dst_len check and bail
out if it's the case. Note that these kfuncs are accessible under root
privileges only.

The Linux kernel CVE team has assigned CVE-2025-39917 to this issue.


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

	Issue introduced in 6.10 with commit 3e1c6f35409f9e447bf37f64840f5b65576bfb78 and fixed in 6.12.48 with commit 0126358df12d6f476f79251d9c398ac5c1b3062d
	Issue introduced in 6.10 with commit 3e1c6f35409f9e447bf37f64840f5b65576bfb78 and fixed in 6.16.8 with commit c4be24ef0510c146dca4671effb127e97631534b
	Issue introduced in 6.10 with commit 3e1c6f35409f9e447bf37f64840f5b65576bfb78 and fixed in 6.17 with commit f9bb6ffa7f5ad0f8ee0f53fc4a10655872ee4a14

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-2025-39917
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/crypto.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/0126358df12d6f476f79251d9c398ac5c1b3062d
	https://git.kernel.org/stable/c/c4be24ef0510c146dca4671effb127e97631534b
	https://git.kernel.org/stable/c/f9bb6ffa7f5ad0f8ee0f53fc4a10655872ee4a14