Public bug reported:
This fixes what I believe is a bug in libxi which causes my application
to crash. I have reported it to FreeDesktop.org
https://bugs.freedesktop.org/show_bug.cgi?id=36592
diff ../../libXi-1.3-orig/src/XExtInt.c src/XExtInt.c
1196c1196
ptr = cookie_out-data = malloc(sizeof(XIRawEvent));
---
ptr = cookie_out-data = malloc(len);
In trying to understand a heap corruption when I added XI2 RawMotion event
handling to our Xinput-based application, I came across the following routine
copyRawEvent() in libxi-1.3/src/XExtInt.c. My question is what is the purpose
of computing len if it is not used? Should it have been used as an argument
to malloc().
copyRawEvent(XGenericEventCookie *cookie_in,
XGenericEventCookie *cookie_out)
{
XIRawEvent *in, *out;
void *ptr;
int len;
int bits;
in = cookie_in-data;
bits = count_bits(in-valuators.mask, in-valuators.mask_len);
len = sizeof(XIRawEvent) + in-valuators.mask_len;
len += bits * sizeof(double) * 2;
ptr = cookie_out-data = malloc(sizeof(XIRawEvent));
if (!ptr)
return False;
out = next_block(ptr, sizeof(XIRawEvent));
*out = *in;
out-valuators.mask = next_block(ptr, out-valuators.mask_len);
memcpy(out-valuators.mask, in-valuators.mask, out-valuators.mask_len);
out-valuators.values = next_block(ptr, bits * sizeof(double));
memcpy(out-valuators.values, in-valuators.values, bits * sizeof(double));
out-raw_values = next_block(ptr, bits * sizeof(double));
memcpy(out-raw_values, in-raw_values, bits * sizeof(double));
return True;
}
When I use valgrind, I get the following output as the culprit for the
crash
==4166== Invalid write of size 1
==4166==at 0x4C29F04: memcpy (mc_replace_strmem.c:497)
==4166==by 0x8F39180: ??? (in /usr/lib/libXi.so.6.1.0)
==4166==by 0x7433D48: _XCopyEventCookie (in /usr/lib/libX11.so.6.3.0)
==4166==by 0x7425166: XPeekEvent (in /usr/lib/libX11.so.6.3.0)
==4166==by 0x49C3E3: process_key (x11_be.c:1065)
==4166==by 0x49EA5C: event_key_release (x11_be.c:2201)
==4166==by 0x49DD6E: x11_be_process_events (x11_be.c:1892)
==4166==by 0x4A38F4: x11_be_main_loop (x11_be.c:4353)
==4166==by 0x4A39E1: x11_be_thread_main (x11_be.c:4385)
==4166==by 0x87549C9: start_thread (pthread_create.c:300)
==4166==by 0x8A516FC: clone (clone.S:112)
==4166== Address 0x168afe80 is 0 bytes after a block of size 96 alloc'd
==4166==at 0x4C284A8: malloc (vg_replace_malloc.c:236)
==4166==by 0x8F390BD: ??? (in /usr/lib/libXi.so.6.1.0)
==4166==by 0x7433D48: _XCopyEventCookie (in /usr/lib/libX11.so.6.3.0)
==4166==by 0x7425166: XPeekEvent (in /usr/lib/libX11.so.6.3.0)
==4166==by 0x49C3E3: process_key (x11_be.c:1065)
==4166==by 0x49EA5C: event_key_release (x11_be.c:2201)
==4166==by 0x49DD6E: x11_be_process_events (x11_be.c:1892)
==4166==by 0x4A38F4: x11_be_main_loop (x11_be.c:4353)
==4166==by 0x4A39E1: x11_be_thread_main (x11_be.c:4385)
==4166==by 0x87549C9: start_thread (pthread_create.c:300)
Thanks in advance,
Roger R. Cruz
** Affects: libxi (Ubuntu)
Importance: Undecided
Status: New
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which is subscribed to libxi in Ubuntu.
https://bugs.launchpad.net/bugs/770522
Title:
copyRawEvent() copies data outside of allocated space causing heap
corruption
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