TOMOYO: Fix pathname handling of disconnected paths.

Current tomoyo_realpath_from_path() implementation returns strange pathname
when calculating pathname of a file which belongs to lazy unmounted tree.
Use local pathname rather than strange absolute pathname in that case.

Also, this patch fixes a regression by commit 02125a82 "fix apparmor
dereferencing potentially freed dentry, sanitize __d_path() API".

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/security/tomoyo/realpath.c b/security/tomoyo/realpath.c
index 36fa7c9bedc4..d9f3ced8756e 100644
--- a/security/tomoyo/realpath.c
+++ b/security/tomoyo/realpath.c
@@ -293,8 +293,16 @@ char *tomoyo_realpath_from_path(struct path *path)
                         pos = tomoyo_get_local_path(path->dentry, buf,
                                                     buf_len - 1);
                 /* Get absolute name for the rest. */
-                else
+                else {
                         pos = tomoyo_get_absolute_path(path, buf, buf_len - 1);
+                        /*
+                         * Fall back to local name if absolute name is not
+                         * available.
+                         */
+                        if (pos == ERR_PTR(-EINVAL))
+                                pos = tomoyo_get_local_path(path->dentry, buf,
+                                                            buf_len - 1);
+                }
 encode:
                 if (IS_ERR(pos))
                         continue;