From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793877126; b=gnAi3XAYfiJokB3mZBX1TJ5vLUUFnugUxuJAuBqbX/lq9000Wjp3DY5rQAKmedkyXwRa BuCOPAbBqr3v87bleoORzI2JIhXRuKg27oBeEdB9HRKXg6XIH1RSII24X/v+1uAB67i54 ILTV84gjQoaZkpGv7sS6Iu/qei3N6NYo6ZSJ0DrylD8bL/CjbcSLWxV4VsTW86x9PioJo GXMmujXfiR7kY1+u8Cy2tMMY/3aUd53SQrVEko+5vk6iynG7oCK+wEZ97RlLBGDKjGJxW jsg5Bo4HeXHPA+uWZ0VhWcnpU5N9Wky25VXX+o3T5olDi4ao3r3srCoUS44y1Ymet9Q== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793877126; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=A6Btm3+v+dnXqWTR2GX+hsLiVMvVrLHj5mxZiRv+uQA=; b=x+Fg3FGbSLozNBzy1Opek04AGYC6ITc6GPk9M08J5baLiHM5ar13QgR49fHlmxOxkbxu RwpiK2QXz/qoQA9u5bK1snnS1OKlPlgzuj9p+8i8kE+Sh2RC6n9ju33U3lAFI+V6qHqlq AD5Bc7J5TFF68yqqXt7MUV3no0pabxP2UIeutJ0DjQr0GlIvgZltYttalcGLQxrtGki9v elqqLjJPU/W9GZ1SN2TRxdD17Fn1Tiye6drUwxpzAtKWDPjjXV9PCpBsZ/LY+OuZGoflj ynG5yVCyljEEsFfqZtknhQmFLsQCOA+PzZQyRqoDqL79Z+O5b8C8EKEk1FVxj0P3lQg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=WAbXpW5G; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9D48606A337; Thu, 5 Nov 2026 11:12:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=WAbXpW5G Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3B671F000C1; Thu, 5 Nov 2026 11:12:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793877125; bh=A6Btm3+v+dnXqWTR2GX+hsLiVMvVrLHj5mxZiRv+uQA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=WAbXpW5G+J81zpga2YkofDFAJr37p7VW0gGXFRU1+QCgzM/A2pZgHgznNZ2nCalqE Ia3JyUZPh6L8Rg/y+uDgpDdpHVkNXyzDJVU61C50bKdJpxk3QmFsmifPi+WacjV/XA QcdaQ2JwYWDZM/S9fBxO98d3uu84tMP2L3LX4JZ6BhPLw+JPH/18HgMzAJJzcMfDF3 tw4HNNjQMzFdjFhehxPRAgVYMCdqVn+EzZzkd0u3g2A/L89+VMUZrPX21d6cbm+Hxu OFZ2xzICDiinoYKDYRJ6cNwQKSRtQb9bUblJfArFReo7oJfCXLWSKUy3cXW4MihmdO KKFQUwanA6LGA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v4 7/8] selinux: Restrict dma-buf direct cgroup charging Reply-To: sashiko-reviews@lists.linux.dev To: "Albert Esteve" , "Tejun Heo" , "Johannes Weiner" , =?utf-8?b?TWljaGFsIEtvdXRuw70=?= , "Jonathan Corbet" , "Shuah Khan" , "Sumit Semwal" , =?utf-8?b?Q2hyaXN0aWFuIEvDtm5pZw==?= , "Michal Hocko" , "Roman Gushchin" , "Shakeel Butt" , "Muchun Song" , "Andrew Morton" , "Benjamin Gaignard" , "Brian Starkey" , "John Stultz" , "T.J. Mercier" , "Christian Brauner" , "Paul Moore" , "James Morris" , "Serge E. Hallyn" , "Stephen Smalley" , "Shuah Khan" , "Randy Dunlap" , =?utf-8?b?T25kcmVqIE1vc27DocSNZWs=?= , "Jens Wiklander" , "Sumit Garg" Cc: dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, op-tee@lists.trustedfirmware.org, media-ci@linuxtv.org In-Reply-To: <20261104-v2_20230123_tjmercier_google_com-v4-7-1819a017000b@redhat.com> References: <20261104-v2_20230123_tjmercier_google_com-v4-0-1819a017000b@redhat.com> <20261104-v2_20230123_tjmercier_google_com-v4-7-1819a017000b@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Thu, 05 Nov 2026 11:12:03 +0000 X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Thank you for your contribution! Sashiko AI review found 2 potential issue(= s) to consider: - [High] selinux: selinux_dma_buf_charge_cgroup() bypasses check on genfsco= n cgroups - [Medium] selinux: one-off dma_buf charge_cgroup lacks broader cgroup cont= rol design -- commit d0dd0ed1dd84ec5c8f4de9a298a749d83668b53e Author: Albert Esteve selinux: Restrict dma-buf direct cgroup charging This commit implements the selinux_dma_buf_charge_cgroup() hook and adds the charge_cgroup permission to the dma_buf security class to restrict which processes can charge dma-buf memory to a target cgroup. > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 8f39d91eabc97..2f99eaa910af4 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -2210,6 +2210,40 @@ static int selinux_dma_buf_charge_task(const struc= t cred *from, const struct cre > SECCLASS_DMA_BUF, DMA_BUF__CHARGE_TASK, NULL); > } > =20 > +#ifdef CONFIG_CGROUPS > +static int selinux_dma_buf_charge_cgroup(const struct cred *cred, struct= cgroup *cgrp) > +{ > + u32 cgrp_sid, clen; > + int rc; > + char *context; > + > + rc =3D kernfs_xattr_get(cgrp->kn, XATTR_NAME_SELINUX, NULL, 0); > + if (rc =3D=3D -ENODATA) > + return 0; [Severity: High] As reported by Sashiko on v3 [1], in security/selinux/hooks.c, does returni= ng 0 in selinux_dma_buf_charge_cgroup() when kernfs_xattr_get() returns -ENODA= TA bypass the permission check for all default-labeled cgroups? When a process calls ioctl(DMA_HEAP_IOCTL_ALLOC) or ioctl(DMA_BUF_IOCTL_XFER_CHARGE) with a charge_fd referencing a cgroup directory, mem_cgroup_get_from_fd() invokes security_dma_buf_charge_cgroup() -> selinux_dma_buf_charge_cgroup(). In SELinux, cgroup and cgroup2 filesystems are configured with SE_SBGENFS | SE_SBGENFS_XATTR in selinux_set_mnt_opts() and obtain their default label (such as cgroup_t) from policy genfscon rules. When a cgroupfs VFS inode is initialized in inode_doinit_with_dentry(), SELinux computes the default SID via selinux_genfs_get_sid() and only uses kernfs xattrs as an optional override: security/selinux/hooks.c:inode_doinit_with_dentry() { ... rc =3D selinux_genfs_get_sid(dentry, sclass, sbsec->flags, &sid); if (rc) { dput(dentry); goto out; } if ((sbsec->flags & SE_SBGENFS_XATTR) && (inode->i_opflags & IOP_XATTR)) { rc =3D inode_doinit_use_xattr(inode, dentry, sid, &sid); ... } When no explicit setxattr() has been performed on the cgroup directory, inode_doinit_use_xattr() gets -ENODATA and falls back to def_sid in memory without writing any security.selinux xattr to cgrp->kn: security/selinux/hooks.c:inode_doinit_use_xattr() { ... if (rc < 0) { kfree(context); if (rc !=3D -ENODATA) { pr_warn("SELinux: %s: getxattr returned %d for dev=3D%s ino=3D%llu\n", __func__, -rc, inode->i_sb->s_id, inode->i_ino); return rc; } *sid =3D def_sid; return 0; } ... } Similarly, selinux_kernfs_init_security() sees -ENODATA on the parent node and returns 0 without setting an xattr on child cgroup nodes, and if the cgroup_seclabel policy capability is not enabled, security.selinux xattrs cannot be set on cgroup directories at all. Because kernfs_xattr_get(cgrp->kn, XATTR_NAME_SELINUX, NULL, 0) returns -ENODATA for every cgroup that has not been manually relabeled via setxattr(), won't selinux_dma_buf_charge_cgroup() skip avc_has_perm() for a= ll default-labeled cgroup_t cgroups and render policy rules like "allow allocator_app_t cgroup_t:dma_buf charge_cgroup;" ineffective? [ ... ] > diff --git a/security/selinux/include/classmap.h b/security/selinux/inclu= de/classmap.h > index b4ebedc6e4240..90d1e04c3d27c 100644 > --- a/security/selinux/include/classmap.h > +++ b/security/selinux/include/classmap.h > @@ -181,7 +181,7 @@ const struct security_class_mapping secclass_map[] = =3D { > { "user_namespace", { "create", NULL } }, > { "memfd_file", > { COMMON_FILE_PERMS, "execute_no_trans", "entrypoint", NULL } }, > - { "dma_buf", { "charge_task", NULL } }, > + { "dma_buf", { "charge_task", "charge_cgroup", NULL } }, [Severity: Medium] As reported by Paul Moore on RFC [2], in security/selinux/include/classmap.h (secclass_map) and security/selinux/hooks.c (selinux_dma_buf_charge_cgroup(= )), this adds a narrow dma_buf class permission for cgroup charging invoked from DMA_HEAP_IOCTL_ALLOC and DMA_BUF_IOCTL_XFER_CHARGE via mem_cgroup_get_from_fd() -> security_dma_buf_charge_cgroup(). Rather than introducing a one-off dma_buf cgroup charging permission, should this be part of a broader SELinux access control design covering existing cgroup control points so that the object class and permission model is consistent across cgroup operations? [1] https://lore.kernel.org/r/20261027-v2_20230123_tjmercier_google_com-v3-= 6-78d2c4cb8647@redhat.com [2] https://lore.kernel.org/r/16093a0278a6d7d1a0a8bc055c228bed@paul-moore.c= om --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261104-v2_2023012= 3_tjmercier_google_com-v4-0-1819a017000b@redhat.com?part=3D7