irda: Only insert new objects into the global database via setsockopt

The irda_setsockopt() function conditionally allocates memory for a new
self->ias_object or, in some cases, reuses the existing
self->ias_object. Existing objects were incorrectly reinserted into the
LM_IAS database which corrupted the doubly linked list used for the
hashbin implementation of the LM_IAS database. When combined with a
memory leak in irda_bind(), this issue could be leveraged to create a
use-after-free vulnerability in the hashbin list. This patch fixes the
issue by only inserting newly allocated objects into the database.

CVE-2018-6555

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Seth Arnold <seth.arnold@canonical.com>
Reviewed-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/irda/af_irda.c b/net/irda/af_irda.c
index 96459b265d09b438292032aef0211ae31fe9474e..b4743db43b53a1dbd2a7ac7b20ee0f6dd99825d5 100644 (file)
--- a/net/irda/af_irda.c
+++ b/net/irda/af_irda.c
@@ -2053,7 +2053,11 @@ static int irda_setsockopt(struct socket *sock, int level, int optname,
                        err = -EINVAL;
                        goto out;
                }
-               irias_insert_object(ias_obj);
+
+               /* Only insert newly allocated objects */
+               if (free_ias)
+                       irias_insert_object(ias_obj);
+
                kfree(ias_opt);
                break;
        case IRLMP_IAS_DEL: