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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 <peter.hutterer@who-t.net>
This commit is contained in:
Peter Hutterer 2023-10-03 11:53:05 +10:00
parent 997e17eabe
commit 541ab2ecd4
2 changed files with 4 additions and 4 deletions
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4
Xi/xiproperty.c
View File

@ -730,7 +730,7 @@ XIChangeDeviceProperty(DeviceIntPtr dev, Atom property, Atom type,
XIDestroyDeviceProperty(prop); XIDestroyDeviceProperty(prop);
return BadAlloc; return BadAlloc;
} }
new_value.size = len; new_value.size = total_len;
new_value.type = type; new_value.type = type;
new_value.format = format; new_value.format = format;
@ -747,7 +747,7 @@ XIChangeDeviceProperty(DeviceIntPtr dev, Atom property, Atom type,
case PropModePrepend: case PropModePrepend:
new_data = new_value.data; new_data = new_value.data;
old_data = (void *) (((char *) new_value.data) + old_data = (void *) (((char *) new_value.data) +
(prop_value->size * size_in_bytes)); (len * size_in_bytes));
break; break;
} }
if (new_data) if (new_data)

4
randr/rrproperty.c
View File

@ -209,7 +209,7 @@ RRChangeOutputProperty(RROutputPtr output, Atom property, Atom type,
RRDestroyOutputProperty(prop); RRDestroyOutputProperty(prop);
return BadAlloc; return BadAlloc;
} }
new_value.size = len; new_value.size = total_len;
new_value.type = type; new_value.type = type;
new_value.format = format; new_value.format = format;
@ -226,7 +226,7 @@ RRChangeOutputProperty(RROutputPtr output, Atom property, Atom type,
case PropModePrepend: case PropModePrepend:
new_data = new_value.data; new_data = new_value.data;
old_data = (void *) (((char *) new_value.data) + old_data = (void *) (((char *) new_value.data) +
(prop_value->size * size_in_bytes)); (len * size_in_bytes));
break; break;
} }
if (new_data) if (new_data)