Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932980AbbLBPtd (ORCPT ); Wed, 2 Dec 2015 10:49:33 -0500 Received: from mail-ig0-f172.google.com ([209.85.213.172]:37731 "EHLO mail-ig0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932773AbbLBPmM (ORCPT ); Wed, 2 Dec 2015 10:42:12 -0500 From: Seth Forshee To: "Eric W. Biederman" , Casey Schaufler Cc: Alexander Viro , Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , Miklos Szeredi , linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, Seth Forshee , James Morris , "Serge E. Hallyn" Subject: [PATCH 06/19] Smack: Handle labels consistently in untrusted mounts Date: Wed, 2 Dec 2015 09:40:06 -0600 Message-Id: <1449070821-73820-7-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com> References: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3255 Lines: 92 The SMACK64, SMACK64EXEC, and SMACK64MMAP labels are all handled differently in untrusted mounts. This is confusing and potentically problematic. Change this to handle them all the same way that SMACK64 is currently handled; that is, read the label from disk and check it at use time. For SMACK64 and SMACK64MMAP access is denied if the label does not match smk_root. To be consistent with suid, a SMACK64EXEC label which does not match smk_root will still allow execution of the file but will not run with the label supplied in the xattr. Signed-off-by: Seth Forshee Acked-by: Casey Schaufler --- security/smack/smack_lsm.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 16cac04214e2..0e555f64ded0 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -921,6 +921,7 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm) struct inode *inode = file_inode(bprm->file); struct task_smack *bsp = bprm->cred->security; struct inode_smack *isp; + struct superblock_smack *sbsp; int rc; if (bprm->cred_prepared) @@ -930,6 +931,11 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm) if (isp->smk_task == NULL || isp->smk_task == bsp->smk_task) return 0; + sbsp = inode->i_sb->s_security; + if ((sbsp->smk_flags & SMK_SB_UNTRUSTED) && + isp->smk_task != sbsp->smk_root) + return 0; + if (bprm->unsafe & (LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP)) { struct task_struct *tracer; rc = 0; @@ -1733,6 +1739,7 @@ static int smack_mmap_file(struct file *file, struct task_smack *tsp; struct smack_known *okp; struct inode_smack *isp; + struct superblock_smack *sbsp; int may; int mmay; int tmay; @@ -1744,6 +1751,10 @@ static int smack_mmap_file(struct file *file, isp = file_inode(file)->i_security; if (isp->smk_mmap == NULL) return 0; + sbsp = file_inode(file)->i_sb->s_security; + if (sbsp->smk_flags & SMK_SB_UNTRUSTED && + isp->smk_mmap != sbsp->smk_root) + return -EACCES; mkp = isp->smk_mmap; tsp = current_security(); @@ -3532,16 +3543,14 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode) if (rc >= 0) transflag = SMK_INODE_TRANSMUTE; } - if (!(sbsp->smk_flags & SMK_SB_UNTRUSTED)) { - /* - * Don't let the exec or mmap label be "*" or "@". - */ - skp = smk_fetch(XATTR_NAME_SMACKEXEC, inode, dp); - if (IS_ERR(skp) || skp == &smack_known_star || - skp == &smack_known_web) - skp = NULL; - isp->smk_task = skp; - } + /* + * Don't let the exec or mmap label be "*" or "@". + */ + skp = smk_fetch(XATTR_NAME_SMACKEXEC, inode, dp); + if (IS_ERR(skp) || skp == &smack_known_star || + skp == &smack_known_web) + skp = NULL; + isp->smk_task = skp; skp = smk_fetch(XATTR_NAME_SMACKMMAP, inode, dp); if (IS_ERR(skp) || skp == &smack_known_star || -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/