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dri2: better checks for integer overflow in GetBuffers* 

Check for integer overflow before using stuff->count in a multiplication,
to avoid compiler optimizing out due to undefined behaviour, but only
after we've checked to make sure stuff->count is in the range of the
request we're parsing.

Reported-by: jes@posteo.de
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>
(cherry picked from commit 6ca496b7c3)
This commit is contained in:
Alan Coopersmith 2015-09-21 22:36:41 -07:00 committed by Adam Jackson
parent 616239c15d
commit 62e2aa02ef
1 changed files with 11 additions and 3 deletions
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14
hw/xfree86/dri2/dri2ext.c
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@ -269,9 +269,11 @@ ProcDRI2GetBuffers(ClientPtr client)
int status, width, height, count;
unsigned int *attachments;
REQUEST_FIXED_SIZE(xDRI2GetBuffersReq, stuff->count * 4);
if (stuff->count > (INT_MAX / 4))
REQUEST_AT_LEAST_SIZE(xDRI2GetBuffersReq);
/* stuff->count is a count of CARD32 attachments that follows */
if (stuff->count > (INT_MAX / sizeof(CARD32)))
return BadLength;
REQUEST_FIXED_SIZE(xDRI2GetBuffersReq, stuff->count * sizeof(CARD32));
if (!validDrawable(client, stuff->drawable, DixReadAccess | DixWriteAccess,
&pDrawable, &status))
@ -297,7 +299,13 @@ ProcDRI2GetBuffersWithFormat(ClientPtr client)
int status, width, height, count;
unsigned int *attachments;
REQUEST_FIXED_SIZE(xDRI2GetBuffersReq, stuff->count * (2 * 4));
REQUEST_AT_LEAST_SIZE(xDRI2GetBuffersReq);
/* stuff->count is a count of pairs of CARD32s (attachments & formats)
that follows */
if (stuff->count > (INT_MAX / (2 * sizeof(CARD32))))
return BadLength;
REQUEST_FIXED_SIZE(xDRI2GetBuffersReq,
stuff->count * (2 * sizeof(CARD32)));
if (!validDrawable(client, stuff->drawable, DixReadAccess | DixWriteAccess,
&pDrawable, &status))
return status;