dump_common_audit_data(): fix racy accesses to ->d_name

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>

diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 7d8026f..a0cd28c 100644 (file)
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -275,7 +275,9 @@ 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) {
@@ -293,8 +295,9 @@ 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=");