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 A23402EBDD2; Wed, 13 Aug 2025 20:55:34 +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=1755118538; cv=none; b=eTHlDvyxJKPF7A3bbmW6ZgZsBJ4N5Hb9wwDnbZxNDp63J5LXyWUsE0jfE+PEhy9sYl+mjcnge1DTkhshNnRe2xUgdjJhlbXJYhYVLfiIKTIrh6vVJn/fbmL+aGiMNLQB7qyMphiBFOnNnGcwZIOQgB1y74dLMuIJbe9SKEjq/i8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755118538; c=relaxed/simple; bh=o+QnQXBbsNnhzc+F7XR5RGGcsAzuJwGoRpwGKKVP7iY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MZYiG6BqF3Lbh6FcQT+rWMiQH3rNJPZ0yFO9Mn61uKvANwTfkVJQ7KHDw72pJc865WAz5pyFAydQYMGyIi8f90DhguISUx79RsnfZMs3i0L7qYj4ZbPfXv1Xpfqjpv7F1f5nsawIzWXb8+IzVg48WgqRUzOlfuWh9xB2YlV6pgc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QNBFjLH6; 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="QNBFjLH6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53B2DC4CEEB; Wed, 13 Aug 2025 20:55:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755118534; bh=o+QnQXBbsNnhzc+F7XR5RGGcsAzuJwGoRpwGKKVP7iY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QNBFjLH6XJmorVw7m/V+G+ydoKpJlWxlSi4khAVSppDyRrLoI/+lcnz9kGhOozG1I ik6Na3jHYhGBdt8TTyQU6xQQauhY1vgopQfosrOIRn8F3f5MNcBqshYb2KngqY9gzd Y5b1xRJS0LBKOL/TIEp7W/izdAg6TzCgO3l4BNpa+Q2DGzSYVDcyrNt+VUvBamlYdy yadvJcg1myzDCK5tAgE4UcTcBw3vPm6mjLlM5ArfmdsQ/edJQKXUE8i5rzbJrPhBRA ytlRVy7THEmsn5WhpqTeUL+CC7ci8KxJLtnr/elqMZgz8oUmZ9aBEqw/brbRbDaNvN LAs1ANQrCqVpg== 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 v3 01/12] bpf: Update the bpf_prog_calc_tag to use SHA256 Date: Wed, 13 Aug 2025 22:55:15 +0200 Message-ID: <20250813205526.2992911-2-kpsingh@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250813205526.2992911-1-kpsingh@kernel.org> References: <20250813205526.2992911-1-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 ++++- include/linux/filter.h | 6 ----- kernel/bpf/Kconfig | 2 +- kernel/bpf/core.c | 50 +++++++----------------------------------- 4 files changed, 14 insertions(+), 50 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index e7ee089e8a31..b98c5b5bf2a1 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; @@ -1711,7 +1712,10 @@ 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/include/linux/filter.h b/include/linux/filter.h index 1e7fd3ee759e..1bcc81ab3227 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -997,12 +997,6 @@ static inline u32 bpf_prog_insn_size(const struct bpf_prog *prog) return prog->len * sizeof(struct bpf_insn); } -static inline u32 bpf_prog_tag_scratch_size(const struct bpf_prog *prog) -{ - return round_up(bpf_prog_insn_size(prog) + - sizeof(__be64) + 1, SHA1_BLOCK_SIZE); -} - static inline unsigned int bpf_prog_size(unsigned int proglen) { return max(sizeof(struct bpf_prog), 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 5d1650af899d..d1a7ea759c82 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -293,28 +294,18 @@ void __bpf_prog_free(struct bpf_prog *fp) int bpf_prog_calc_tag(struct bpf_prog *fp) { - const u32 bits_offset = SHA1_BLOCK_SIZE - sizeof(__be64); - u32 raw_size = bpf_prog_tag_scratch_size(fp); - u32 digest[SHA1_DIGEST_WORDS]; - u32 ws[SHA1_WORKSPACE_WORDS]; - u32 i, bsize, psize, blocks; + u32 insn_size = bpf_prog_insn_size(fp); struct bpf_insn *dst; bool was_ld_map; - u8 *raw, *todo; - __be32 *result; - __be64 *bits; + int i, ret = 0; - raw = vmalloc(raw_size); - if (!raw) + dst = vmalloc(insn_size); + if (!dst) return -ENOMEM; - sha1_init_raw(digest); - memset(ws, 0, sizeof(ws)); - /* We need to take out the map fd for the digest calculation * since they are unstable from user space side. */ - dst = (void *)raw; for (i = 0, was_ld_map = false; i < fp->len; i++) { dst[i] = fp->insnsi[i]; if (!was_ld_map && @@ -334,34 +325,9 @@ int bpf_prog_calc_tag(struct bpf_prog *fp) was_ld_map = false; } } - - psize = bpf_prog_insn_size(fp); - memset(&raw[psize], 0, raw_size - psize); - raw[psize++] = 0x80; - - bsize = round_up(psize, SHA1_BLOCK_SIZE); - blocks = bsize / SHA1_BLOCK_SIZE; - todo = raw; - if (bsize - psize >= sizeof(__be64)) { - bits = (__be64 *)(todo + bsize - sizeof(__be64)); - } else { - bits = (__be64 *)(todo + bsize + bits_offset); - blocks++; - } - *bits = cpu_to_be64((psize - 1) << 3); - - while (blocks--) { - sha1_transform(digest, todo, ws); - todo += SHA1_BLOCK_SIZE; - } - - result = (__force __be32 *)digest; - for (i = 0; i < SHA1_DIGEST_WORDS; i++) - result[i] = cpu_to_be32(digest[i]); - memcpy(fp->tag, result, sizeof(fp->tag)); - - vfree(raw); - return 0; + sha256((u8 *)dst, insn_size, fp->digest); + vfree(dst); + return ret; } static int bpf_adj_delta_to_imm(struct bpf_insn *insn, u32 pos, s32 end_old, -- 2.43.0