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authorCasey Schaufler <casey@schaufler-ca.com>2013-12-30 09:38:00 -0800
committerCasey Schaufler <casey@schaufler-ca.com>2013-12-31 13:35:16 -0800
commit24ea1b6efcd8fc3b465fb74964e1a0cbe9979730 (patch)
treebb45d3814997cbfe99a72fa9c874b752fcd6b83a /security
parent4afde48be8929b6da63a9e977aaff0894ba82984 (diff)
downloadlinux-24ea1b6efcd8fc3b465fb74964e1a0cbe9979730.tar.gz
Smack: Rationalize mount restrictions
The mount restrictions imposed by Smack rely heavily on the use of the filesystem "floor", which is the label that all processes writing to the filesystem must have access to. It turns out that while the "floor" notion is sound, it has yet to be fully implemented and has never been used. The sb_mount and sb_umount hooks only make sense if the filesystem floor is used actively, and it isn't. They can be reintroduced if a rational restriction comes up. Until then, they get removed. The sb_kern_mount hook is required for the option processing. It is too permissive in the case of unprivileged mounts, effectively bypassing the CAP_MAC_ADMIN restrictions if any of the smack options are specified. Unprivileged mounts are no longer allowed to set Smack filesystem options. Additionally, the root and default values are set to the label of the caller, in keeping with the policy that objects get the label of their creator. Targeted for git://git.gitorious.org/smack-next/kernel.git Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Diffstat (limited to 'security')
-rw-r--r--security/smack/smack_lsm.c83
1 files changed, 29 insertions, 54 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 67b7381d024..d5528324a63 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -229,7 +229,7 @@ static int smack_syslog(int typefrom_file)
if (smack_privileged(CAP_MAC_OVERRIDE))
return 0;
- if (smack_syslog_label != NULL && smack_syslog_label != skp)
+ if (smack_syslog_label != NULL && smack_syslog_label != skp)
rc = -EACCES;
return rc;
@@ -339,10 +339,12 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
struct inode *inode = root->d_inode;
struct superblock_smack *sp = sb->s_security;
struct inode_smack *isp;
+ struct smack_known *skp;
char *op;
char *commap;
char *nsp;
int transmute = 0;
+ int specified = 0;
if (sp->smk_initialized)
return 0;
@@ -357,34 +359,56 @@ static int smack_sb_kern_mount(struct super_block *sb, int flags, void *data)
if (strncmp(op, SMK_FSHAT, strlen(SMK_FSHAT)) == 0) {
op += strlen(SMK_FSHAT);
nsp = smk_import(op, 0);
- if (nsp != NULL)
+ if (nsp != NULL) {
sp->smk_hat = nsp;
+ specified = 1;
+ }
} else if (strncmp(op, SMK_FSFLOOR, strlen(SMK_FSFLOOR)) == 0) {
op += strlen(SMK_FSFLOOR);
nsp = smk_import(op, 0);
- if (nsp != NULL)
+ if (nsp != NULL) {
sp->smk_floor = nsp;
+ specified = 1;
+ }
} else if (strncmp(op, SMK_FSDEFAULT,
strlen(SMK_FSDEFAULT)) == 0) {
op += strlen(SMK_FSDEFAULT);
nsp = smk_import(op, 0);
- if (nsp != NULL)
+ if (nsp != NULL) {
sp->smk_default = nsp;
+ specified = 1;
+ }
} else if (strncmp(op, SMK_FSROOT, strlen(SMK_FSROOT)) == 0) {
op += strlen(SMK_FSROOT);
nsp = smk_import(op, 0);
- if (nsp != NULL)
+ if (nsp != NULL) {
sp->smk_root = nsp;
+ specified = 1;
+ }
} else if (strncmp(op, SMK_FSTRANS, strlen(SMK_FSTRANS)) == 0) {
op += strlen(SMK_FSTRANS);
nsp = smk_import(op, 0);
if (nsp != NULL) {
sp->smk_root = nsp;
transmute = 1;
+ specified = 1;
}
}
}
+ if (!smack_privileged(CAP_MAC_ADMIN)) {
+ /*
+ * Unprivileged mounts don't get to specify Smack values.
+ */
+ if (specified)
+ return -EPERM;
+ /*
+ * Unprivileged mounts get root and default from the caller.
+ */
+ skp = smk_of_current();
+ sp->smk_root = skp->smk_known;
+ sp->smk_default = skp->smk_known;
+ }
/*
* Initialize the root inode.
*/
@@ -421,53 +445,6 @@ static int smack_sb_statfs(struct dentry *dentry)
return rc;
}
-/**
- * smack_sb_mount - Smack check for mounting
- * @dev_name: unused
- * @path: mount point
- * @type: unused
- * @flags: unused
- * @data: unused
- *
- * Returns 0 if current can write the floor of the filesystem
- * being mounted on, an error code otherwise.
- */
-static int smack_sb_mount(const char *dev_name, struct path *path,
- const char *type, unsigned long flags, void *data)
-{
- struct superblock_smack *sbp = path->dentry->d_sb->s_security;
- struct smk_audit_info ad;
-
- smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
- smk_ad_setfield_u_fs_path(&ad, *path);
-
- return smk_curacc(sbp->smk_floor, MAY_WRITE, &ad);
-}
-
-/**
- * smack_sb_umount - Smack check for unmounting
- * @mnt: file system to unmount
- * @flags: unused
- *
- * Returns 0 if current can write the floor of the filesystem
- * being unmounted, an error code otherwise.
- */
-static int smack_sb_umount(struct vfsmount *mnt, int flags)
-{
- struct superblock_smack *sbp;
- struct smk_audit_info ad;
- struct path path;
-
- path.dentry = mnt->mnt_root;
- path.mnt = mnt;
-
- smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH);
- smk_ad_setfield_u_fs_path(&ad, path);
-
- sbp = path.dentry->d_sb->s_security;
- return smk_curacc(sbp->smk_floor, MAY_WRITE, &ad);
-}
-
/*
* BPRM hooks
*/
@@ -3762,8 +3739,6 @@ struct security_operations smack_ops = {
.sb_copy_data = smack_sb_copy_data,
.sb_kern_mount = smack_sb_kern_mount,
.sb_statfs = smack_sb_statfs,
- .sb_mount = smack_sb_mount,
- .sb_umount = smack_sb_umount,
.bprm_set_creds = smack_bprm_set_creds,
.bprm_committing_creds = smack_bprm_committing_creds,