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 331fd3bd0f39bd7ab7db67a5370c82f94d96a4ba..d4f9e2b69caa63598c442fbb54fb9d86248fa587 100644 (file)
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -264,7 +264,9 @@ 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) {
@@ -282,8 +284,9 @@ 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=");