dump_common_audit_data(): fix racy accesses to ->d_name

commit d36a1dd9f77ae1e72da48f4123ed35627848507d upstream.

We are not guaranteed the locking environment that would prevent
dentry getting renamed right under us.  And it's possible for
old long name to be freed after rename, leading to UAF here.

Cc: stable@kernel.org # v2.6.2+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index e40874373f2b4a72b30648bb58a09f82fbd58a52..d025f575a9e30464cd033900862624e4ebe86bc5 100644 (file)
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -274,7 +274,9 @@ static void dump_common_audit_data(struct audit_buffer *ab,
                struct inode *inode;
 
                audit_log_format(ab, " name=");
+               spin_lock(&a->u.dentry->d_lock);
                audit_log_untrustedstring(ab, a->u.dentry->d_name.name);
+               spin_unlock(&a->u.dentry->d_lock);
 
                inode = d_backing_inode(a->u.dentry);
                if (inode) {
@@ -292,8 +294,9 @@ static void dump_common_audit_data(struct audit_buffer *ab,
                dentry = d_find_alias(inode);
                if (dentry) {
                        audit_log_format(ab, " name=");
-                       audit_log_untrustedstring(ab,
-                                        dentry->d_name.name);
+                       spin_lock(&dentry->d_lock);
+                       audit_log_untrustedstring(ab, dentry->d_name.name);
+                       spin_unlock(&dentry->d_lock);
                        dput(dentry);
                }
                audit_log_format(ab, " dev=");