[PATCH] AppArmor: Handle the rename flags.

[Tetsuo Handa]

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>
Signed-off-by: John Johansen <john.johansen@xxxxxxxxxxxxx>
---
 security/apparmor/lsm.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index c0b4366..d7d92ad 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -332,6 +332,7 @@ static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
 					  old_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,
@@ -340,6 +341,16 @@ static int apparmor_path_rename(struct path *old_dir, struct dentry *old_dentry,
 			error = aa_path_perm(OP_RENAME_DEST, profile, &new_path,
 					     0, MAY_WRITE | AA_MAY_META_WRITE |
 					     AA_MAY_CREATE, &cond);
+		if (!error && (flags & RENAME_EXCHANGE)) {
+			struct path tmp_path = new_path;
+			new_path = old_path;
+			old_path = tmp_path;
+			/* Cross rename requires both inodes to exist. */
+			cond.uid = new_dentry->d_inode->i_uid;
+			cond.mode = new_dentry->d_inode->i_mode;
+			flags = 0;
+			goto retry;
+		}
 
 	}
 	return error;
-- 
2.0.0.rc0

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