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Fixed bug 2330 - Debian bug report: SDL2 X11 driver buffer overflow with large X11 file descriptor

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manuel.montezelo

Original bug report (note that it was against 2.0.0, it might have been fixed in between):  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=733015

--------------------------------------------------------
Package: libsdl2-2.0-0
Version: 2.0.0+dfsg1-3
Severity: normal
Tags: patch

I have occasional crashes here caused by the X11 backend of SDL2. It seems to
be caused by the X11_Pending function trying to add a high number (> 1024)
file descriptor to a fd_set before doing a select on it to avoid busy waiting
on X11 events. This causes a buffer overflow because the file descriptor is
larger (or equal) than the limit FD_SETSIZE.

Attached is a possible workaround patch.

Please also keep in mind that fd_set are also used in following files which
may have similar problems.

src/audio/bsd/SDL_bsdaudio.c
src/audio/paudio/SDL_paudio.c
src/audio/qsa/SDL_qsa_audio.c
src/audio/sun/SDL_sunaudio.c
src/joystick/linux/SDL_sysjoystick.c


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On Tuesday 24 December 2013 00:43:13 Sven Eckelmann wrote:
> I have occasional crashes here caused by the X11 backend of SDL2. It seems
> to be caused by the X11_Pending function trying to add a high number (>
> 1024) file descriptor to a fd_set before doing a select on it to avoid busy
> waiting on X11 events. This causes a buffer overflow because the file
> descriptor is larger (or equal) than the limit FD_SETSIZE.


I personally experienced this problem while hacking on the python bindings
package for SDL2 [1] (while doing make runtest). But it easier to reproduce in
a smaller, synthetic testcase.
This commit is contained in:
Sam Lantinga
2017-08-14 20:22:19 -07:00
parent 9451cd81ae
commit fb835f9e3b
18 changed files with 63 additions and 144 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
src/audio/sun/SDL_sunaudio.c
View File

@@ -40,6 +40,7 @@
#include "SDL_timer.h"
#include "SDL_audio.h"
#include "../../core/unix/SDL_poll.h"
#include "../SDL_audio_c.h"
#include "../SDL_audiodev_c.h"
#include "SDL_sunaudio.h"
@@ -97,11 +98,7 @@ SUNAUDIO_WaitDevice(_THIS)
}
}
#else
fd_set fdset;
FD_ZERO(&fdset);
FD_SET(this->hidden->audio_fd, &fdset);
select(this->hidden->audio_fd + 1, NULL, &fdset, NULL, NULL);
SDL_IOReady(this->hidden->audio_fd, SDL_TRUE, -1);
#endif
}