From a31ba141824a7649e11f0ef7673718ce559d6337 Mon Sep 17 00:00:00 2001 From: Peter Hutterer Date: Tue, 3 Oct 2023 11:53:05 +1000 Subject: [PATCH xserver 1/4] Xi/randr: fix handling of PropModeAppend/Prepend The handling of appending/prepending properties was incorrect, with at least two bugs: the property length was set to the length of the new part only, i.e. appending or prepending N elements to a property with P existing elements always resulted in the property having N elements instead of N + P. Second, when pre-pending a value to a property, the offset for the old values was incorrect, leaving the new property with potentially uninitalized values and/or resulting in OOB memory writes. For example, prepending a 3 element value to a 5 element property would result in this 8 value array: [N, N, N, ?, ?, P, P, P ] P, P ^OOB write The XI2 code is a copy/paste of the RandR code, so the bug exists in both. CVE-2023-5367, ZDI-CAN-22153 This vulnerability was discovered by: Jan-Niklas Sohn working with Trend Micro Zero Day Initiative Signed-off-by: Peter Hutterer --- Xi/xiproperty.c | 4 ++-- randr/rrproperty.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/Xi/xiproperty.c b/Xi/xiproperty.c index 6ec419e870..563c4f31a5 100644 --- a/Xi/xiproperty.c +++ b/Xi/xiproperty.c @@ -730,7 +730,7 @@ XIChangeDeviceProperty(DeviceIntPtr dev, Atom property, Atom type, XIDestroyDeviceProperty(prop); return BadAlloc; } - new_value.size = len; + new_value.size = total_len; new_value.type = type; new_value.format = format; @@ -747,7 +747,7 @@ XIChangeDeviceProperty(DeviceIntPtr dev, Atom property, Atom type, case PropModePrepend: new_data = new_value.data; old_data = (void *) (((char *) new_value.data) + - (prop_value->size * size_in_bytes)); + (len * size_in_bytes)); break; } if (new_data) diff --git a/randr/rrproperty.c b/randr/rrproperty.c index c2fb9585c6..25469f57b2 100644 --- a/randr/rrproperty.c +++ b/randr/rrproperty.c @@ -209,7 +209,7 @@ RRChangeOutputProperty(RROutputPtr output, Atom property, Atom type, RRDestroyOutputProperty(prop); return BadAlloc; } - new_value.size = len; + new_value.size = total_len; new_value.type = type; new_value.format = format; @@ -226,7 +226,7 @@ RRChangeOutputProperty(RROutputPtr output, Atom property, Atom type, case PropModePrepend: new_data = new_value.data; old_data = (void *) (((char *) new_value.data) + - (prop_value->size * size_in_bytes)); + (len * size_in_bytes)); break; } if (new_data) -- 2.41.0