From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27C2D2D73B0; Sun, 21 Sep 2025 13:31:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758461501; cv=none; b=Cvd7QT2Pu7dkFNFxv3K2l95rQS/LQL09FJA3xWT+EGfuvKRkCc4IkEEVQOIK9rHAFrExzrt8IjBNkYLb54dpWet0pEf7K5HYZ/fRjz8Mv1vIH4EwrXlKoEr7fKufB7k2zK3a7zDMz2yIfIdbOaChX4oj9Cg7Ea41ZSpYHEkLpSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758461501; c=relaxed/simple; bh=mVzuBM7YN1GiYFKCgsjuvP48gHWPaH9Xlg2yE5+AwIY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FUSOQJpAfYoXTJrXdSP237VVpSmrLF6gdO6FZ6tjCD4R3ZDiOOS02rTL8/zBMmdfmGxPjzJG5+a10tMRDRWVrM/cXi6b5Lzb/Rjbvsf1mMFSHiDx1wLzVoG93NTblZ85umU1wmAEORVAhrENI3qlu9C2nSwylj6nUm1+eUHy1kQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KwKzduc/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KwKzduc/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B28EFC116B1; Sun, 21 Sep 2025 13:31:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758461500; bh=mVzuBM7YN1GiYFKCgsjuvP48gHWPaH9Xlg2yE5+AwIY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KwKzduc/R9vRH4ugDQnDFi8FNXV2zFYb7AXzy1YYBNtYaesJjXeKIHjKO/DQgEl38 JOsHaZ8iDnSQet1uracdgZaDP9sb2e2sFGpX+22DOU+9xw8jQx6+jeGo8DUVrAzkpY lmbi4dJBZAaAbDPbCHlg/aJ0QSIGcE18UmHUoeCQmoG5KxbR4+5TtuizOi66I2Ay5r /1GrLDtaMxUXrYPuLS6EqnHnqbBRVC1UUNm7+FwtUP8n0TSFg+HK8Zi1aw6gnXQv28 IB3IGdDFlbBGYtwmR2Y9Z6uulcRITwrU5rP9oo3E0dPpgQZ9uFqGcAW+ms3bIvtg3W WVE8CDQKYF8sA== From: KP Singh To: bpf@vger.kernel.org, linux-security-module@vger.kernel.org Cc: bboscaccy@linux.microsoft.com, paul@paul-moore.com, kys@microsoft.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, KP Singh Subject: [PATCH v5 01/12] bpf: Update the bpf_prog_calc_tag to use SHA256 Date: Sun, 21 Sep 2025 15:31:22 +0200 Message-ID: <20250921133133.82062-2-kpsingh@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250921133133.82062-1-kpsingh@kernel.org> References: <20250921133133.82062-1-kpsingh@kernel.org> Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Exclusive maps restrict map access to specific programs using a hash. The current hash used for this is SHA1, which is prone to collisions. This patch uses SHA256, which is more resilient against collisions. This new hash is stored in bpf_prog and used by the verifier to determine if a program can access a given exclusive map. The original 64-bit tags are kept, as they are used by users as a short, possibly colliding program identifier for non-security purposes. Signed-off-by: KP Singh --- include/linux/bpf.h | 6 +++++- kernel/bpf/Kconfig | 2 +- kernel/bpf/core.c | 5 ++--- 3 files changed, 8 insertions(+), 5 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 41f776071ff5..d75902074bd1 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -31,6 +31,7 @@ #include #include #include +#include struct bpf_verifier_env; struct bpf_verifier_log; @@ -1717,7 +1718,10 @@ struct bpf_prog { enum bpf_attach_type expected_attach_type; /* For some prog types */ u32 len; /* Number of filter blocks */ u32 jited_len; /* Size of jited insns in bytes */ - u8 tag[BPF_TAG_SIZE]; + union { + u8 digest[SHA256_DIGEST_SIZE]; + u8 tag[BPF_TAG_SIZE]; + }; struct bpf_prog_stats __percpu *stats; int __percpu *active; unsigned int (*bpf_func)(const void *ctx, diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig index 17067dcb4386..eb3de35734f0 100644 --- a/kernel/bpf/Kconfig +++ b/kernel/bpf/Kconfig @@ -3,7 +3,7 @@ # BPF interpreter that, for example, classic socket filters depend on. config BPF bool - select CRYPTO_LIB_SHA1 + select CRYPTO_LIB_SHA256 # Used by archs to tell that they support BPF JIT compiler plus which # flavour. Only one of the two can be selected for a specific arch since diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 1cda2589d4b3..9b64674df16b 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include @@ -296,7 +297,6 @@ void __bpf_prog_free(struct bpf_prog *fp) int bpf_prog_calc_tag(struct bpf_prog *fp) { size_t size = bpf_prog_insn_size(fp); - u8 digest[SHA1_DIGEST_SIZE]; struct bpf_insn *dst; bool was_ld_map; u32 i; @@ -327,8 +327,7 @@ int bpf_prog_calc_tag(struct bpf_prog *fp) was_ld_map = false; } } - sha1((const u8 *)dst, size, digest); - memcpy(fp->tag, digest, sizeof(fp->tag)); + sha256((u8 *)dst, size, fp->digest); vfree(dst); return 0; } -- 2.43.0