Fix CVE-2016-4994: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-4994 Copied from upstream repository: https://git.gnome.org/browse/gimp/patch/?id=e82aaa4b4ee0703c879e35ea9321fff6be3e9b6f From e82aaa4b4ee0703c879e35ea9321fff6be3e9b6f Mon Sep 17 00:00:00 2001 From: Shmuel H Date: Mon, 20 Jun 2016 17:14:41 +0300 Subject: Bug 767873 - (CVE-2016-4994) Multiple Use-After-Free when parsing... ...XCF channel and layer properties The properties PROP_ACTIVE_LAYER, PROP_FLOATING_SELECTION, PROP_ACTIVE_CHANNEL saves the current object pointer the @info structure. Others like PROP_SELECTION (for channel) and PROP_GROUP_ITEM (for layer) will delete the current object and create a new object, leaving the pointers in @info invalid (dangling). Therefore, if a property from the first type will come before the second, the result will be an UaF in the last lines of xcf_load_image (when it actually using the pointers from @info). I wasn't able to exploit this bug because that g_object_instance->c_class gets cleared by the last g_object_unref and GIMP_IS_{LAYER,CHANNEL} detects that and return FALSE. (cherry picked from commit 6d804bf9ae77bc86a0a97f9b944a129844df9395) --- app/xcf/xcf-load.c | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/app/xcf/xcf-load.c b/app/xcf/xcf-load.c index b180377..67cc6d4 100644 --- a/app/xcf/xcf-load.c +++ b/app/xcf/xcf-load.c @@ -904,6 +904,18 @@ xcf_load_layer_props (XcfInfo *info, case PROP_GROUP_ITEM: { GimpLayer *group; + gboolean is_active_layer; + + /* We're going to delete *layer, Don't leave its pointers + * in @info. After that, we'll restore them back with the + * new pointer. See bug #767873. + */ + is_active_layer = (*layer == info->active_layer); + if (is_active_layer) + info->active_layer = NULL; + + if (*layer == info->floating_sel) + info->floating_sel = NULL; group = gimp_group_layer_new (image); @@ -916,6 +928,13 @@ xcf_load_layer_props (XcfInfo *info, g_object_ref_sink (*layer); g_object_unref (*layer); *layer = group; + + if (is_active_layer) + info->active_layer = *layer; + + /* Don't restore info->floating_sel because group layers + * can't be floating selections + */ } break; @@ -986,6 +1005,12 @@ xcf_load_channel_props (XcfInfo *info, { GimpChannel *mask; + /* We're going to delete *channel, Don't leave its pointer + * in @info. See bug #767873. + */ + if (*channel == info->active_channel) + info->active_channel = NULL; + mask = gimp_selection_new (image, gimp_item_get_width (GIMP_ITEM (*channel)), @@ -1000,6 +1025,10 @@ xcf_load_channel_props (XcfInfo *info, *channel = mask; (*channel)->boundary_known = FALSE; (*channel)->bounds_known = FALSE; + + /* Don't restore info->active_channel because the + * selection can't be the active channel + */ } break; -- cgit v0.12