From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7299C3CB555 for ; Tue, 1 Sep 2026 01:47:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788227303; cv=none; b=ihoT1i2z5Jwvmi4f2jl52fyYOXJWNMzidK2XbSxRHmNDij39D+GH9AIzgGh3zBiKdmTNxcBBLV776pTdhiQLjWVsbtSMvlvQeOSh3kP1/JxdvIFBTiZhwtdFyEbCa0C0evIDugGRbmUKl0HORen0VFbO3cCq0VpTEwNG25OsjCY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788227303; c=relaxed/simple; bh=sEqoE/JOspzAh4I7PK3klxs+bcydlAXZlE1An4cO3Ow=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=o+5eCFZ8v3l8rZ7+RNSMq01amkh2YJo/Aav+ZYxdEnhs5Ny60lF9R7+qGPqvXoVvnfa19jprvZDVpCdowGRsVbfmJwxkcxR73sevsn6DuUEXwq8m5BuYil7LapZRFtx3kCqgzfjHEGAHn7GCVbhVGV9z4kZal2gwf+1FFL2i+CE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WT/nKl5D; arc=none smtp.client-ip=209.85.214.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WT/nKl5D" Received: by mail-pl1-f181.google.com with SMTP id d9443c01a7336-2d9004f39d3so24961685ad.2 for ; Mon, 31 Aug 2026 18:47:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1788227265; x=1788832065; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to:content-type; bh=+/E7TIF3u/RGKDlz/vbcdmW4BNPGxEY5+7Q5goscvkM=; b=WT/nKl5Dzj/WdzvVmNlFS3qRcJ375vzVwNdet9nLaZ8IIDZtK9gzZoDSX6hPXjq6Cr 9rmnpEDOPNzGvDWiZqJahzs7Nc+zFsq58rXSgQd5fJR5y5LlfN4Mdl7bOgp4JR+sJIgM y/FO0WmUaI8rhMbPdHqKT4Wbqw+eJ5n5e/z0twM08EC59vGmEtxFEg/warf3OPl52xWO 4ZPc73X1HddUtSJQdIhXQl0l6URyWuNn3CRCx8KvzISwLzXkAcbp+M+A788RkO0WJoS9 SXVUxko9F8D1jLL47HNWBoJzOrqaKWUTB0tgWu28QDWE4wIdn/cXtR3K6pWDVLmjE3fi MuHg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788227265; x=1788832065; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=+/E7TIF3u/RGKDlz/vbcdmW4BNPGxEY5+7Q5goscvkM=; b=Rde3z3uxcJnZSZer1naioG0apB2Tzo1SvDeWA7pvbHG9kwit1/KTf6s/1kY6DpAVWU OYHcwn6ECDWUJOKZUBq0Wp5m11Qn18hbPqJOHBjyCc/X70ANl4D0GcbnaEX8plKrGNdw lnoEdYC74fomT6ZVG0Qvw9pgLzfR+RxY2/Scs/FlhqXg9fD3rc9kuxLM46Iy7woWt8Gq /uXBxtDnwm8dzAj1HHAomnzuQvD/kU47g+lsA0M50e0rXn1b0NJOzn/HcoPcievkxPpg OPDoPtTrrGwEwpNHNmGle2N+P2nnejVFGcA/IhtiPGrTGXkscG9gW+6yTfbxpgoGCVZU dkTw== X-Forwarded-Encrypted: i=1; AKwUvBx7L1Ubvg6d8rmKzg5YVd6MPNkdFF1QNs1AfsupF2k5TG96s4+rkJjUBRypxmsXjT5hwOk=@vger.kernel.org X-Gm-Message-State: AFuF++krBesiGLEJ1Wswqs+dHToVU0cb4LUSdliSOrpeUg8WLfmn1r4X 8CBnF/FIwslUexA+5ea3sEGytl7LLuQnF2RRWpNlunrzX/GHOiakHxgH X-Gm-Gg: AYBFou0m+RixmuRN52WLedns3M0+Ib8CzXyjONyA1IV6mnBDvUwmr6qOqwHTuEhRTo7 97M2XRiy7UVcZg6r3gB4aCOPaww4iLxvDwhpUXfN1tU+ubYvbXyIx+T9niu1f9mX8l4eqzSboQQ qgipU4t+Mebvdi5+OjV9ACE47NZTPU1Pn160Ct5ufC+GjJ1Vaq3DwfNFOa0ihlcpc5Q8WgEUtII C23szoNm9QRs9sY8Fg5IGQaK1XwsYQz+DJLrtjklX9uT9tJeG8FbQ678lHqvd17ua6di844PfLp hN1oAK6PqNR2VYp1C34fax2kjr2otZdmK1Pdon5NPbgilcUM8G6OGm4Eg9bDaqq44rxtTcx7nrd 2AwXpqSOMmor9dkC8ZB0ppkvyFzUR1DlZSgHukYZVC+6GTyCOHp3Ag67fssDclkNZIFIOzwpmcL YvOJ6y+zBzPRODEzs7BrGngqXQCFBAG0D/7W3BQYMeGN4uJMHi6Y4yKReO2b6/YcLqjOFD+8jRN HfGTJ4bDKtOONA+tYi0wmUjBhRiI12IukmAUIkpM74rErf54sMQZA== X-Received: by 2002:a17:903:4686:b0:2cf:c543:2c7e with SMTP id d9443c01a7336-2d94a8f455amr62657115ad.10.1788227265233; Mon, 31 Aug 2026 18:47:45 -0700 (PDT) Received: from secrnd-cstp.tailb7f510.ts.net ([125.131.91.97]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2d911a9651csm27053495ad.21.2026.08.31.18.47.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Aug 2026 18:47:42 -0700 (PDT) From: Sanghyun Park To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , bpf@vger.kernel.org Cc: Sanghyun Park , Leon Hwang , John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Ihor Solodrai , Shuah Khan , Stanislav Fomichev , Pu Lehui , Suchit Karunakaran , Xu Kuohai , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf-next v5 1/2] bpf: Validate program attach type during link update Date: Tue, 1 Sep 2026 10:47:09 +0900 Message-ID: <20260901014713.3502900-2-sanghyun.park.cnu@gmail.com> X-Mailer: git-send-email 2.48.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Cgroup link updates compare only the program type. Programs verified for different hooks can share a type, so a UDP6 sock_addr program can replace a UDP4 program and write beyond the four-byte ipc.addr field in the stack-local struct ipcm_cookie. The same gap permits incompatible LSM_MAC and LSM_CGROUP replacements. Validate every replacement program against the link attach type before dispatching to the link-specific update operation. Keep the CGROUP_SKB CAP_NET_ADMIN check at initial attach so pinned or delegated link FDs can still be updated after a capability drop. Fixes: 0c991ebc8c69 ("bpf: Implement bpf_prog replacement for an active bpf_cgroup_link") Acked-by: Leon Hwang Signed-off-by: Sanghyun Park --- v5: - Fold the link-create permission check call onto one line. v4: https://lore.kernel.org/r/20260831023918.1857658-1-sanghyun.park.cnu@gmail.com - Validate every program link update through the shared attach-type helper. - Fold the LSM attach-flavor check into that helper. - Keep the CGROUP_SKB permission check in the attach-only wrapper and rename the wrapper to describe that role. - Follow the preferred BPF multi-line comment style. - Add focused regression selftests as patch 2/2. v3: https://lore.kernel.org/r/20260821084726.3769957-2-sanghyun.park.cnu@gmail.com - Factor the CGROUP_SKB CAP_NET_ADMIN check into an attach-only helper. v2: https://lore.kernel.org/r/20260818061021.2551771-2-sanghyun.park.cnu@gmail.com - Extend validation from cgroup sock_addr programs to all cgroup program types, including exact LSM attach flavors. - Preserve legacy CGROUP_SKB ingress/egress replacement compatibility. - Keep the CGROUP_SKB CAP_NET_ADMIN check on attach, not link update. v1: https://lore.kernel.org/r/20260805052858.2390918-3-sanghyun.park.cnu@gmail.com --- kernel/bpf/syscall.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 6874ba1424af..2bcd3f3a2a55 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -4481,14 +4481,9 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog, case BPF_PROG_TYPE_CGROUP_SOCK_ADDR: case BPF_PROG_TYPE_CGROUP_SOCKOPT: case BPF_PROG_TYPE_SK_LOOKUP: + case BPF_PROG_TYPE_LSM: return attach_type == prog->expected_attach_type ? 0 : -EINVAL; case BPF_PROG_TYPE_CGROUP_SKB: - if (!bpf_token_capable(prog->aux->token, CAP_NET_ADMIN)) - /* cg-skb progs can be loaded by unpriv user. - * check permissions at attach time. - */ - return -EPERM; - ptype = attach_type_to_prog_type(attach_type); if (prog->type != ptype) return -EINVAL; @@ -4542,6 +4537,20 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog, } } +static int bpf_prog_attach_check_perm(const struct bpf_prog *prog, + enum bpf_attach_type attach_type) +{ + /* + * CGROUP_SKB programs can be loaded by unprivileged users, so check + * permissions at attach time. + */ + if (prog->type == BPF_PROG_TYPE_CGROUP_SKB && + !bpf_token_capable(prog->aux->token, CAP_NET_ADMIN)) + return -EPERM; + + return bpf_prog_attach_check_attach_type(prog, attach_type); +} + static bool is_cgroup_prog_type(enum bpf_prog_type ptype, enum bpf_attach_type atype, bool check_atype) { @@ -4606,7 +4615,7 @@ static int bpf_prog_attach(const union bpf_attr *attr) if (IS_ERR(prog)) return PTR_ERR(prog); - if (bpf_prog_attach_check_attach_type(prog, attr->attach_type)) { + if (bpf_prog_attach_check_perm(prog, attr->attach_type)) { bpf_prog_put(prog); return -EINVAL; } @@ -5805,8 +5814,7 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr) if (IS_ERR(prog)) return PTR_ERR(prog); - ret = bpf_prog_attach_check_attach_type(prog, - attr->link_create.attach_type); + ret = bpf_prog_attach_check_perm(prog, attr->link_create.attach_type); if (ret) goto out; @@ -5968,6 +5976,10 @@ static int link_update(union bpf_attr *attr) goto out_put_progs; } + ret = bpf_prog_attach_check_attach_type(new_prog, link->attach_type); + if (ret) + goto out_put_progs; + if (link->ops->update_prog) ret = link->ops->update_prog(link, new_prog, old_prog); else -- 2.48.1