[PATCH (for 3.15) 3/5] AppArmor: Handle the rename flags.

[Tetsuo Handa]

>From 819e94ae3a6d9235196d137a39afa4e0bbd79770 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Mon, 12 May 2014 21:54:05 +0900
Subject: [PATCH (for 3.15) 3/5] AppArmor: Handle the rename flags.

For AppArmor, the RENAME_EXCHANGE flag means "check permissions with
reversed arguments" and "distinguish condition of source and target".
Future patches will stop re-calculating pathnames.

Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
 security/apparmor/lsm.c |   22 ++++++++++++++++++++--
 1 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index c0b4366..9f21296 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -331,7 +331,14 @@ static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
 		struct path_cond cond = { old_dentry->d_inode->i_uid,
 					  old_dentry->d_inode->i_mode
 		};
+		struct path_cond new_cond = cond;
 
+		if (flags & RENAME_EXCHANGE) {
+			/* Cross rename requires both inodes to exist. */
+			new_cond.uid = new_dentry->d_inode->i_uid;
+			new_cond.mode = new_dentry->d_inode->i_mode;
+		}
+retry:
 		error = aa_path_perm(OP_RENAME_SRC, profile, &old_path, 0,
 				     MAY_READ | AA_MAY_META_READ | MAY_WRITE |
 				     AA_MAY_META_WRITE | AA_MAY_DELETE,
@@ -339,7 +346,18 @@ static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
 		if (!error)
 			error = aa_path_perm(OP_RENAME_DEST, profile, &new_path,
 					     0, MAY_WRITE | AA_MAY_META_WRITE |
-					     AA_MAY_CREATE, &cond);
+					     AA_MAY_CREATE, &new_cond);
+		if (!error && (flags & RENAME_EXCHANGE)) {
+			struct path tmp_path = new_path;
+			struct path_cond tmp_cond = new_cond;
+
+			new_path = old_path;
+			old_path = tmp_path;
+			new_cond = cond;
+			cond = tmp_cond;
+			flags = 0;
+			goto retry;
+		}
 
 	}
 	return error;
-- 
1.7.1
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