selinux: parse contexts for mount options early

Commit b8b87fd954b4 ("selinux: Fix selinux_sb_mnt_opts_compat()")
started to parse mount options into SIDs in selinux_add_opt() if policy
has already been loaded. Since it's extremely unlikely that anyone would
depend on the ability to set SELinux contexts on fs_context before
loading the policy and then mounting that context after simplify the
logic by always parsing the options early.

Note that the multi-step mounting is only possible with the new
fscontext mount API and wasn't possible before its introduction.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index b24a1ae..ab32303 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -340,7 +340,6 @@ static void inode_free_security(struct inode *inode)
 }
 
 struct selinux_mnt_opts {
-       const char *fscontext, *context, *rootcontext, *defcontext;
        u32 fscontext_sid;
        u32 context_sid;
        u32 rootcontext_sid;
@@ -349,12 +348,7 @@ struct selinux_mnt_opts {
 
 static void selinux_free_mnt_opts(void *mnt_opts)
 {
-       struct selinux_mnt_opts *opts = mnt_opts;
-       kfree(opts->fscontext);
-       kfree(opts->context);
-       kfree(opts->rootcontext);
-       kfree(opts->defcontext);
-       kfree(opts);
+       kfree(mnt_opts);
 }
 
 enum {
@@ -601,17 +595,6 @@ static int bad_option(struct superblock_security_struct *sbsec, char flag,
        return 0;
 }
 
-static int parse_sid(struct super_block *sb, const char *s, u32 *sid)
-{
-       int rc = security_context_str_to_sid(&selinux_state, s,
-                                            sid, GFP_KERNEL);
-       if (rc)
-               pr_warn("SELinux: security_context_str_to_sid"
-                      "(%s) failed for (dev %s, type %s) errno=%d\n",
-                      s, sb ? sb->s_id : "?", sb ? sb->s_type->name : "?", rc);
-       return rc;
-}
-
 /*
  * Allow filesystems with binary mount data to explicitly set mount point
  * labeling information.
@@ -674,49 +657,29 @@ static int selinux_set_mnt_opts(struct super_block *sb,
         * than once with different security options.
         */
        if (opts) {
-               if (opts->fscontext) {
-                       if (opts->fscontext_sid == SECSID_NULL) {
-                               rc = parse_sid(sb, opts->fscontext, &fscontext_sid);
-                               if (rc)
-                                       goto out;
-                       } else
-                               fscontext_sid = opts->fscontext_sid;
+               if (opts->fscontext_sid) {
+                       fscontext_sid = opts->fscontext_sid;
                        if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
                                        fscontext_sid))
                                goto out_double_mount;
                        sbsec->flags |= FSCONTEXT_MNT;
                }
-               if (opts->context) {
-                       if (opts->context_sid == SECSID_NULL) {
-                               rc = parse_sid(sb, opts->context, &context_sid);
-                               if (rc)
-                                       goto out;
-                       } else
-                               context_sid = opts->context_sid;
+               if (opts->context_sid) {
+                       context_sid = opts->context_sid;
                        if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
                                        context_sid))
                                goto out_double_mount;
                        sbsec->flags |= CONTEXT_MNT;
                }
-               if (opts->rootcontext) {
-                       if (opts->rootcontext_sid == SECSID_NULL) {
-                               rc = parse_sid(sb, opts->rootcontext, &rootcontext_sid);
-                               if (rc)
-                                       goto out;
-                       } else
-                               rootcontext_sid = opts->rootcontext_sid;
+               if (opts->rootcontext_sid) {
+                       rootcontext_sid = opts->rootcontext_sid;
                        if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
                                        rootcontext_sid))
                                goto out_double_mount;
                        sbsec->flags |= ROOTCONTEXT_MNT;
                }
-               if (opts->defcontext) {
-                       if (opts->defcontext_sid == SECSID_NULL) {
-                               rc = parse_sid(sb, opts->defcontext, &defcontext_sid);
-                               if (rc)
-                                       goto out;
-                       } else
-                               defcontext_sid = opts->defcontext_sid;
+               if (opts->defcontext_sid) {
+                       defcontext_sid = opts->defcontext_sid;
                        if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
                                        defcontext_sid))
                                goto out_double_mount;
@@ -986,6 +949,8 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
 {
        struct selinux_mnt_opts *opts = *mnt_opts;
        bool is_alloc_opts = false;
+       u32 *dst_sid;
+       int rc;
 
        if (token == Opt_seclabel)
                /* eaten and completely ignored */
@@ -993,6 +958,11 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
        if (!s)
                return -ENOMEM;
 
+       if (!selinux_initialized(&selinux_state)) {
+               pr_warn("SELinux: Unable to set superblock options before the security server is initialized\n");
+               return -EINVAL;
+       }
+
        if (!opts) {
                opts = kzalloc(sizeof(*opts), GFP_KERNEL);
                if (!opts)
@@ -1003,36 +973,34 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
 
        switch (token) {
        case Opt_context:
-               if (opts->context || opts->defcontext)
+               if (opts->context_sid || opts->defcontext_sid)
                        goto err;
-               opts->context = s;
-               if (selinux_initialized(&selinux_state))
-                       parse_sid(NULL, s, &opts->context_sid);
+               dst_sid = &opts->context_sid;
                break;
        case Opt_fscontext:
-               if (opts->fscontext)
+               if (opts->fscontext_sid)
                        goto err;
-               opts->fscontext = s;
-               if (selinux_initialized(&selinux_state))
-                       parse_sid(NULL, s, &opts->fscontext_sid);
+               dst_sid = &opts->fscontext_sid;
                break;
        case Opt_rootcontext:
-               if (opts->rootcontext)
+               if (opts->rootcontext_sid)
                        goto err;
-               opts->rootcontext = s;
-               if (selinux_initialized(&selinux_state))
-                       parse_sid(NULL, s, &opts->rootcontext_sid);
+               dst_sid = &opts->rootcontext_sid;
                break;
        case Opt_defcontext:
-               if (opts->context || opts->defcontext)
+               if (opts->context_sid || opts->defcontext_sid)
                        goto err;
-               opts->defcontext = s;
-               if (selinux_initialized(&selinux_state))
-                       parse_sid(NULL, s, &opts->defcontext_sid);
+               dst_sid = &opts->defcontext_sid;
                break;
+       default:
+               WARN_ON(1);
+               return -EINVAL;
        }
-
-       return 0;
+       rc = security_context_str_to_sid(&selinux_state, s, dst_sid, GFP_KERNEL);
+       if (rc)
+               pr_warn("SELinux: security_context_str_to_sid (%s) failed with errno=%d\n",
+                       s, rc);
+       return rc;
 
 err:
        if (is_alloc_opts) {
@@ -2681,37 +2649,27 @@ static int selinux_sb_mnt_opts_compat(struct super_block *sb, void *mnt_opts)
        if (!opts)
                return (sbsec->flags & SE_MNTMASK) ? 1 : 0;
 
-       if (opts->fscontext) {
-               if (opts->fscontext_sid == SECSID_NULL)
-                       return 1;
-               else if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
-                                      opts->fscontext_sid))
+       if (opts->fscontext_sid) {
+               if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
+                              opts->fscontext_sid))
                        return 1;
        }
-       if (opts->context) {
-               if (opts->context_sid == SECSID_NULL)
-                       return 1;
-               else if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
-                                      opts->context_sid))
+       if (opts->context_sid) {
+               if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
+                              opts->context_sid))
                        return 1;
        }
-       if (opts->rootcontext) {
-               if (opts->rootcontext_sid == SECSID_NULL)
-                       return 1;
-               else {
-                       struct inode_security_struct *root_isec;
+       if (opts->rootcontext_sid) {
+               struct inode_security_struct *root_isec;
 
-                       root_isec = backing_inode_security(sb->s_root);
-                       if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
-                                      opts->rootcontext_sid))
-                               return 1;
-               }
-       }
-       if (opts->defcontext) {
-               if (opts->defcontext_sid == SECSID_NULL)
+               root_isec = backing_inode_security(sb->s_root);
+               if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
+                              opts->rootcontext_sid))
                        return 1;
-               else if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
-                                      opts->defcontext_sid))
+       }
+       if (opts->defcontext_sid) {
+               if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
+                              opts->defcontext_sid))
                        return 1;
        }
        return 0;
@@ -2721,7 +2679,6 @@ static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)
 {
        struct selinux_mnt_opts *opts = mnt_opts;
        struct superblock_security_struct *sbsec = selinux_superblock(sb);
-       int rc;
 
        if (!(sbsec->flags & SE_SBINITIALIZED))
                return 0;
@@ -2729,47 +2686,24 @@ static int selinux_sb_remount(struct super_block *sb, void *mnt_opts)
        if (!opts)
                return 0;
 
-       if (opts->fscontext) {
-               if (opts->fscontext_sid == SECSID_NULL) {
-                       rc = parse_sid(sb, opts->fscontext,
-                                      &opts->fscontext_sid);
-                       if (rc)
-                               return rc;
-               }
+       if (opts->fscontext_sid) {
                if (bad_option(sbsec, FSCONTEXT_MNT, sbsec->sid,
                               opts->fscontext_sid))
                        goto out_bad_option;
        }
-       if (opts->context) {
-               if (opts->context_sid == SECSID_NULL) {
-                       rc = parse_sid(sb, opts->context, &opts->context_sid);
-                       if (rc)
-                               return rc;
-               }
+       if (opts->context_sid) {
                if (bad_option(sbsec, CONTEXT_MNT, sbsec->mntpoint_sid,
                               opts->context_sid))
                        goto out_bad_option;
        }
-       if (opts->rootcontext) {
+       if (opts->rootcontext_sid) {
                struct inode_security_struct *root_isec;
                root_isec = backing_inode_security(sb->s_root);
-               if (opts->rootcontext_sid == SECSID_NULL) {
-                       rc = parse_sid(sb, opts->rootcontext,
-                                      &opts->rootcontext_sid);
-                       if (rc)
-                               return rc;
-               }
                if (bad_option(sbsec, ROOTCONTEXT_MNT, root_isec->sid,
                               opts->rootcontext_sid))
                        goto out_bad_option;
        }
-       if (opts->defcontext) {
-               if (opts->defcontext_sid == SECSID_NULL) {
-                       rc = parse_sid(sb, opts->defcontext,
-                                      &opts->defcontext_sid);
-                       if (rc)
-                               return rc;
-               }
+       if (opts->defcontext_sid) {
                if (bad_option(sbsec, DEFCONTEXT_MNT, sbsec->def_sid,
                               opts->defcontext_sid))
                        goto out_bad_option;
@@ -2838,42 +2772,12 @@ static int selinux_fs_context_dup(struct fs_context *fc,
                                  struct fs_context *src_fc)
 {
        const struct selinux_mnt_opts *src = src_fc->security;
-       struct selinux_mnt_opts *opts;
 
        if (!src)
                return 0;
 
-       fc->security = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
-       if (!fc->security)
-               return -ENOMEM;
-
-       opts = fc->security;
-
-       if (src->fscontext) {
-               opts->fscontext = kstrdup(src->fscontext, GFP_KERNEL);
-               if (!opts->fscontext)
-                       return -ENOMEM;
-       }
-       if (src->context) {
-               opts->context = kstrdup(src->context, GFP_KERNEL);
-               if (!opts->context)
-                       return -ENOMEM;
-       }
-       if (src->rootcontext) {
-               opts->rootcontext = kstrdup(src->rootcontext, GFP_KERNEL);
-               if (!opts->rootcontext)
-                       return -ENOMEM;
-       }
-       if (src->defcontext) {
-               opts->defcontext = kstrdup(src->defcontext, GFP_KERNEL);
-               if (!opts->defcontext)
-                       return -ENOMEM;
-       }
-       opts->fscontext_sid = src->fscontext_sid;
-       opts->context_sid = src->context_sid;
-       opts->rootcontext_sid = src->rootcontext_sid;
-       opts->defcontext_sid = src->defcontext_sid;
-       return 0;
+       fc->security = kmemdup(src, sizeof(*src), GFP_KERNEL);
+       return fc->security ? 0 : -ENOMEM;
 }
 
 static const struct fs_parameter_spec selinux_fs_parameters[] = {