c494debaa7
If a device has both a button class and a key class and numButtons is
zero, we can get an OOB write due to event under-allocation.
This function seems to assume a device has either keys or buttons, not
both. It has two virtually identical code paths, both of which assume
they're applying to the first event in the sequence.
A device with both a key and button class triggered a logic bug - only
one xEvent was allocated but the deviceStateNotify pointer was pushed on
once per type. So effectively this logic code:
int count = 1;
if (button && nbuttons > 32) count++;
if (key && nbuttons > 0) count++;
if (key && nkeys > 32) count++; // this is basically always true
// count is at 2 for our keys + zero button device
ev = alloc(count * sizeof(xEvent));
FixDeviceStateNotify(ev);
if (button)
FixDeviceStateNotify(ev++);
if (key)
FixDeviceStateNotify(ev++); // santa drops into the wrong chimney here
If the device has more than 3 valuators, the OOB is pushed back - we're
off by one so it will happen when the last deviceValuator event is
written instead.
Fix this by allocating the maximum number of events we may allocate.
Note that the current behavior is not protocol-correct anyway, this
patch fixes only the allocation issue.
Note that this issue does not trigger if the device has at least one
button. While the server does not prevent a button class with zero
buttons, it is very unlikely.
CVE-2024-0229, ZDI-CAN-22678
This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
(cherry picked from commit
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X Server
The X server accepts requests from client applications to create windows, which are (normally rectangular) "virtual screens" that the client program can draw into.
Windows are then composed on the actual screen by the X server (or by a separate composite manager) as directed by the window manager, which usually communicates with the user via graphical controls such as buttons and draggable titlebars and borders.
For a comprehensive overview of X Server and X Window System, consult the following article: https://en.wikipedia.org/wiki/X_server
All questions regarding this software should be directed at the Xorg mailing list:
https://lists.freedesktop.org/mailman/listinfo/xorg
The primary development code repository can be found at:
https://gitlab.freedesktop.org/xorg/xserver
For patch submission instructions, see:
https://www.x.org/wiki/Development/Documentation/SubmittingPatches
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