apparmor: rework file permission to cache file access in file->ctx

This is a temporary step, towards using the file->ctx for delegation,
and also helps speed up file queries, until the permission lookup
cache is introduced.

Signed-off-by: John Johansen <john.johansen@canonical.com>

diff --git a/security/apparmor/file.c b/security/apparmor/file.c
index eb4c300..b6e8e5b 100644 (file)
--- a/security/apparmor/file.c
+++ b/security/apparmor/file.c
@@ -492,6 +492,80 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
        return error;
 }
 
+static void update_file_ctx(struct aa_file_ctx *fctx, struct aa_label *label,
+                           u32 request)
+{
+       struct aa_label *l, *old;
+
+       /* update caching of label on file_ctx */
+       spin_lock(&fctx->lock);
+       old = rcu_dereference_protected(fctx->label,
+                                       spin_is_locked(&fctx->lock));
+       l = aa_label_merge(old, label, GFP_ATOMIC);
+       if (l) {
+               if (l != old) {
+                       rcu_assign_pointer(fctx->label, l);
+                       aa_put_label(old);
+               } else
+                       aa_put_label(l);
+               fctx->allow |= request;
+       }
+       spin_unlock(&fctx->lock);
+}
+
+static int __file_path_perm(const char *op, struct aa_label *label,
+                           struct aa_label *flabel, struct file *file,
+                           u32 request, u32 denied)
+{
+       struct aa_profile *profile;
+       struct aa_perms perms = {};
+       struct path_cond cond = {
+               .uid = file_inode(file)->i_uid,
+               .mode = file_inode(file)->i_mode
+       };
+       char *buffer;
+       int flags, error;
+
+       /* revalidation due to label out of date. No revocation at this time */
+       if (!denied && aa_label_is_subset(flabel, label))
+               /* TODO: check for revocation on stale profiles */
+               return 0;
+
+       flags = PATH_DELEGATE_DELETED | (S_ISDIR(cond.mode) ? PATH_IS_DIR : 0);
+       get_buffers(buffer);
+
+       /* check every profile in task label not in current cache */
+       error = fn_for_each_not_in_set(flabel, label, profile,
+                       profile_path_perm(op, profile, &file->f_path, buffer,
+                                         request, &cond, flags, &perms));
+       if (denied && !error) {
+               /*
+                * check every profile in file label that was not tested
+                * in the initial check above.
+                *
+                * TODO: cache full perms so this only happens because of
+                * conditionals
+                * TODO: don't audit here
+                */
+               if (label == flabel)
+                       error = fn_for_each(label, profile,
+                               profile_path_perm(op, profile, &file->f_path,
+                                                 buffer, request, &cond, flags,
+                                                 &perms));
+               else
+                       error = fn_for_each_not_in_set(label, flabel, profile,
+                               profile_path_perm(op, profile, &file->f_path,
+                                                 buffer, request, &cond, flags,
+                                                 &perms));
+       }
+       if (!error)
+               update_file_ctx(file_ctx(file), label, request);
+
+       put_buffers(buffer);
+
+       return error;
+}
+
 /**
  * aa_file_perm - do permission revalidation check & audit for @file
  * @op: operation being checked
@@ -504,10 +578,6 @@ int aa_path_link(struct aa_label *label, struct dentry *old_dentry,
 int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
                 u32 request)
 {
-       struct path_cond cond = {
-               .uid = file_inode(file)->i_uid,
-               .mode = file_inode(file)->i_mode
-       };
        struct aa_file_ctx *fctx;
        struct aa_label *flabel;
        u32 denied;
@@ -537,8 +607,8 @@ int aa_file_perm(const char *op, struct aa_label *label, struct file *file,
        /* TODO: label cross check */
 
        if (file->f_path.mnt && path_mediated_fs(file->f_path.dentry))
-               error = aa_path_perm(op, label, &file->f_path,
-                                    PATH_DELEGATE_DELETED, request, &cond);
+               error = __file_path_perm(op, label, flabel, file, request,
+                                        denied);
 
 done:
        rcu_read_unlock();