From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: [PATCH v4 09/21] Smack: Handle labels consistently in untrusted mounts Date: Tue, 26 Apr 2016 14:36:22 -0500 Message-ID: <1461699396-33000-10-git-send-email-seth.forshee@canonical.com> References: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=canonical-com.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=aeG73OW9Xy1CAYW4s8YPsK1DWTEX4M6k8ROnPiImiQM=; b=dJVxu8CvR2IOnLiMj+nVhBBC3n8eJq/E/4Y+nwv8uyMy2EYW4Hs1l1Fw4IqD9NtpV/ ARLRjLtZ6VjapiRvzdMChXO0glLFF6hR5Z6weArYdRmZSaG18ZKObaCBVKwxSf6RPmIu 4iH+xXI0RDmJSWFko93KB2GD3dpkCmn0oUKjAPYQKO3BtcsY62/Y0a4rbKSMppqOSRIj mabfPjmUdAGnqEkTvIlZ3/yyPBCEgEmrBNE2cknP40OefG9Eu1kuvcw5OrhrxFR+fQK2 N6b533hcp8qAZDyMDMS8ytioZnfDxvvqhPT5M/xsmiIfW6jO1e58XFNczXqc2f77yD+g Im2Q== In-Reply-To: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Eric W. Biederman" , Casey Schaufler Cc: Alexander Viro , Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , Miklos Szeredi , Pavel Tikhomirov , linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@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, cgroups@vger.kernel.org, Seth Forshee , James Morris , "Serge E. Hallyn" 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 aa17198cd5f2..ca564590cc1b 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -919,6 +919,7 @@ 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) @@ -928,6 +929,11 @@ 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; @@ -1725,6 +1731,7 @@ 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; @@ -1736,6 +1743,10 @@ 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(); @@ -3546,16 +3557,14 @@ 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 || -- 2.7.4