linux-kernel - [PATCH v2] smack: introduce a special case for tmpfs in smack_d

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Date:	Tue, 16 Dec 2014 16:53:08 +0100
From:	Łukasz Stelmach <l.stelmach@...sung.com>
To:	Casey Schaufler <casey@...aufler-ca.com>,
	James Morris <james.l.morris@...cle.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Karol Lewandowski <k.lewandowsk@...sung.com>,
	l.skalski@...sung.com, m.wereski@...tner.samsung.com,
	r.krypa@...sung.com,
	Łukasz Stelmach <l.stelmach@...sung.com>
Subject: [PATCH v2] smack: introduce a special case for tmpfs in
 smack_d_instantiate()

Files created with __shmem_file_stup() appear to have somewhat fake
dentries which make them look like root directories and not get
the label the current process or ("*") star meant for tmpfs files.

Signed-off-by: Łukasz Stelmach <l.stelmach@...sung.com>
---
 security/smack/smack_lsm.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index e8bed86..b774029 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3036,18 +3036,30 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode)
 	 * If that is the case use the root value out
 	 * of the superblock.
 	 */
 	if (opt_dentry->d_parent == opt_dentry) {
-		if (sbp->s_magic == CGROUP_SUPER_MAGIC) {
+		switch (sbp->s_magic) {
+		case CGROUP_SUPER_MAGIC:
 			/*
 			 * The cgroup filesystem is never mounted,
 			 * so there's no opportunity to set the mount
 			 * options.
 			 */
 			sbsp->smk_root = &smack_known_star;
 			sbsp->smk_default = &smack_known_star;
+			isp->smk_inode = sbsp->smk_root;
+			break;
+		case TMPFS_MAGIC:
+			/*
+			 * What about shmem/tmpfs anonymous files with dentry
+			 * obtained from d_alloc_pseudo()?
+			 */
+			isp->smk_inode = smk_of_current();
+			break;
+		default:
+			isp->smk_inode = sbsp->smk_root;
+			break;
 		}
-		isp->smk_inode = sbsp->smk_root;
 		isp->smk_flags |= SMK_INODE_INSTANT;
 		goto unlockandout;
 	}
 
-- 
1.9.1

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