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 33028c098ef3c6314c39c4e62ccf223dde7c7eb3..d6fea68d22ad6d1f6880759ec72287ec994ed6c4 100644 (file)
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -277,7 +277,9 @@ 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) {
@@ -295,8 +297,9 @@ 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=");