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=1793199879; b=OLlYYRI00D0r/ijcmy9p/n9iCatjFApCLnx/GoQKbWtJ56RtGj5TP1U/7WsYTntZFxyw 1IPDUYX4Q52Tjn4m/2oSr15EUqV+P+Jd3pTrsg2QW07yAIILAcP97TDd7RBVdYPjedAx/ caOlM2Yo8IdMEgs8tU3wgAe48PmtAXHAkpzG5FxEUhp3jWbAGB88J6ZeH8rTlxh+UqjtM 0Xh5qrjicG7gxBxAi6pJ5PWZ6OQ8zMqlnBy8YHikevSf3UwP2bTWwkL/sB1J/J90QGLgp wKNYLoXNuPq1xFZmYrQyt1T/BTscj5WZE62DBSwrkxtIwDV9pTAfj4Pm310lyav8rXQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793199879; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=1TKqOP98FHIDcaJNoj3/GWwGDtZsh2WFMN9gl9UcQOs=; b=a4UqVkn8GyneSdcT96CbZuJmmdmv36hYtqhRHnSV5EUbBPqU59+qeO9s0GMnG7LTiKkl azbw7a34/oP/GOf8i5odJTS30xEnfw1X9ucNZcQvE7VGbhcGZrRc33oCC0ppaFfdGmBaI zr3zrM45hRkY9o6JBlkj8vd9ZlhkvAIkPBOZMAXrN5LLXgJyQU3th8NekUntQ8l2WgHdi dDtjOjoWRTmyoysoMJ4HrgbA/5edXyJ0Wfec7rwlg9ZIlWqfkZigEJUzOAfOujbHACmb/ +c0PcGbIEUf80F274tflISMuGMOHb+d0Bg7yu/RdZMtjuwHTPqT8GNUQL7v6dCC84EA== 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=EIRs14Ak; 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 972D8606A31D; Wed, 28 Oct 2026 15:04:39 +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=EIRs14Ak Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FB0F1F01825; Wed, 28 Oct 2026 15:04:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793199879; bh=1TKqOP98FHIDcaJNoj3/GWwGDtZsh2WFMN9gl9UcQOs=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=EIRs14AkkJNqV4FP2ztjO7metvge3koWsF8rvc9H1eOkLYX/cgC+Pq+XLh/h7oAnj MNEGn9M/5cbtIepg3E5EECqqap8BFEljXDT05wKvMgl+Apv61iiIqUYexNfJTjfmPs AoRvFUnbC3JIf3GjxOS+wc+ep8hcuNWLd1w3y7jCZ6hnohvFWH1x2A80texn/ET9Kq yEq4MfQLIx5q38dPZ7eq1EDKuY5cCnLKRotbFLGUKXR/tzKM6v7AlFttlp5sh19hjJ UBMh1XXQFRZUVF7n1jMrjSfKEDoADfSjdgZdcB6KfU5RvH6Y0q7CasX9j84wOnfCZY 3UAJSV4V6VVAA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v3 6/8] 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, echanude@redhat.com, mripard@kernel.org, media-ci@linuxtv.org In-Reply-To: <20261027-v2_20230123_tjmercier_google_com-v3-6-78d2c4cb8647@redhat.com> References: <20261027-v2_20230123_tjmercier_google_com-v3-0-78d2c4cb8647@redhat.com> <20261027-v2_20230123_tjmercier_google_com-v3-6-78d2c4cb8647@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Wed, 28 Oct 2026 15:04:37 +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 1 potential issue(= s) to consider: - [High] selinux: selinux_dma_buf_charge_cgroup() bypasses check on genfsco= n cgroups -- commit 6b412783b17727c382f1a67078326c58c39264e7 Author: Albert Esteve selinux: Restrict dma-buf direct cgroup charging This commit implements the selinux_dma_buf_charge_cgroup() LSM hook and adds the charge_cgroup permission to the dma_buf security class to control which processes may charge dma-buf memory to a cgroup. It reads the target securi= ty context from the cgroup kernfs node's security.selinux extended attribute a= nd checks permission via avc_has_perm(). > 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] Does returning 0 on -ENODATA here bypass the permission check for all cgrou= ps that carry their default genfscon label (such as cgroup_t)? In selinux_set_mnt_opts(), cgroup and cgroup2 filesystems are configured wi= th SE_SBGENFS | SE_SBGENFS_XATTR. When a cgroup VFS inode is initialized in inode_doinit_with_dentry(), SELinux obtains the default SID from policy via selinux_genfs_get_sid() and then checks for an optional xattr override via inode_doinit_use_xattr(): 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() sees -ENODATA from the underlying kernfs node and falls back to def_sid in memory without writing a 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; } ... } Likewise, selinux_kernfs_init_security() sees -ENODATA on the parent kernfs node and returns 0 without storing an xattr on newly created child cgroups. As a result, unless a cgroup directory has been explicitly relabeled with setxattr(), kernfs_xattr_get(cgrp->kn, XATTR_NAME_SELINUX, NULL, 0) will return -ENODATA even though the cgroup is labeled cgroup_t via genfscon. When userspace passes a cgroup fd via DMA_HEAP_IOCTL_ALLOC or DMA_BUF_IOCTL_XFER_CHARGE, mem_cgroup_get_from_fd() invokes security_dma_buf_charge_cgroup() -> selinux_dma_buf_charge_cgroup(), which will return 0 without calling avc_has_perm(), leaving default-labeled cgroup_t cgroups unrestricted? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261027-v2_2023012= 3_tjmercier_google_com-v3-0-78d2c4cb8647@redhat.com?part=3D6