From: José Fonseca <jfonseca@vmware.com>
Date: Wed, 27 Jan 2010 15:41:25 +0000 (+0000)
Subject: svga: Prevent buffer overflow in buffer ranges.
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=422167a9b0dc5b6da7bc7c47621b5da1bc6d315b;p=mesa.git

svga: Prevent buffer overflow in buffer ranges.

Do this by extending the nearest range to cover the new range.

This fixes an access fault in Call of Duty which was doing many disjoint
glBufferSubData calls.
---

diff --git a/src/gallium/drivers/svga/svga_screen_buffer.c b/src/gallium/drivers/svga/svga_screen_buffer.c
index c9e9bef5406..0371ddde368 100644
--- a/src/gallium/drivers/svga/svga_screen_buffer.c
+++ b/src/gallium/drivers/svga/svga_screen_buffer.c
@@ -311,10 +311,20 @@ svga_buffer_upload_queue(struct svga_buffer *sbuf,
                          unsigned end)
 {
    unsigned i;
+   unsigned nearest_range;
+   unsigned nearest_dist;
 
    assert(sbuf->hw.buf);
    assert(end > start);
    
+   if (sbuf->hw.num_ranges < SVGA_BUFFER_MAX_RANGES) {
+      nearest_range = sbuf->hw.num_ranges;
+      nearest_dist = ~0;
+   } else {
+      nearest_range = SVGA_BUFFER_MAX_RANGES - 1;
+      nearest_dist = 0;
+   }
+
    /*
     * Try to grow one of the ranges.
     *
@@ -326,11 +336,33 @@ svga_buffer_upload_queue(struct svga_buffer *sbuf,
     */
 
    for(i = 0; i < sbuf->hw.num_ranges; ++i) {
-      if(start <= sbuf->hw.ranges[i].end && sbuf->hw.ranges[i].start <= end) {
+      int left_dist;
+      int right_dist;
+      int dist;
+
+      left_dist = start - sbuf->hw.ranges[i].end;
+      right_dist = sbuf->hw.ranges[i].start - end;
+      dist = MAX2(left_dist, right_dist);
+
+      if (dist <= 0) {
+         /*
+          * Ranges are contiguous or overlapping -- extend this one and return.
+          */
+
          sbuf->hw.ranges[i].start = MIN2(sbuf->hw.ranges[i].start, start);
-         sbuf->hw.ranges[i].end   = MAX2(sbuf->hw.ranges[i].end,    end);
+         sbuf->hw.ranges[i].end   = MAX2(sbuf->hw.ranges[i].end,   end);
          return;
       }
+      else {
+         /*
+          * Discontiguous ranges -- keep track of the nearest range.
+          */
+
+         if (dist < nearest_dist) {
+            nearest_range = i;
+            nearest_dist = dist;
+         }
+      }
    }
 
    /*
@@ -345,13 +377,27 @@ svga_buffer_upload_queue(struct svga_buffer *sbuf,
    assert(!sbuf->hw.svga);
    assert(!sbuf->hw.boxes);
 
-   /*
-    * Add a new range.
-    */
+   if (sbuf->hw.num_ranges < SVGA_BUFFER_MAX_RANGES) {
+      /*
+       * Add a new range.
+       */
 
-   sbuf->hw.ranges[sbuf->hw.num_ranges].start = start;
-   sbuf->hw.ranges[sbuf->hw.num_ranges].end = end;
-   ++sbuf->hw.num_ranges;
+      sbuf->hw.ranges[sbuf->hw.num_ranges].start = start;
+      sbuf->hw.ranges[sbuf->hw.num_ranges].end = end;
+      ++sbuf->hw.num_ranges;
+   } else {
+      /*
+       * Everything else failed, so just extend the nearest range.
+       *
+       * It is OK to do this because we always keep a local copy of the
+       * host buffer data, for SW TNL, and the host never modifies the buffer.
+       */
+
+      assert(nearest_range < SVGA_BUFFER_MAX_RANGES);
+      assert(nearest_range < sbuf->hw.num_ranges);
+      sbuf->hw.ranges[nearest_range].start = MIN2(sbuf->hw.ranges[nearest_range].start, start);
+      sbuf->hw.ranges[nearest_range].end   = MAX2(sbuf->hw.ranges[nearest_range].end,   end);
+   }
 }