Patchwork [02/18] TCG: fix negative frame offset calculations

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Submitter Blue Swirl
Date May 28, 2011, 10:06 a.m.
Message ID <BANLkTi=KdgiJBObnBLM8R2yU6ESMiS51tw@mail.gmail.com>
Download mbox | patch
Permalink /patch/97777/
State New
Headers show

Comments

Blue Swirl - May 28, 2011, 10:06 a.m.
size_t is unsigned, so the frame offset calculations can be incorrect for
negative offsets.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
---
 tcg/tcg.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

 /* free register 'reg' by spilling the corresponding temporary if necessary */

Patch

diff --git a/tcg/tcg.c b/tcg/tcg.c
index fad92f9..b31d80d 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -1440,13 +1440,17 @@  static void temp_allocate_frame(TCGContext *s, int temp)
 {
     TCGTemp *ts;
     ts = &s->temps[temp];
-    s->current_frame_offset = (s->current_frame_offset +
sizeof(tcg_target_long) - 1) & ~(sizeof(tcg_target_long) - 1);
-    if (s->current_frame_offset + sizeof(tcg_target_long) > s->frame_end)
+    s->current_frame_offset = (s->current_frame_offset +
+                               (tcg_target_long)sizeof(tcg_target_long) - 1) &
+        ~(sizeof(tcg_target_long) - 1);
+    if (s->current_frame_offset + (tcg_target_long)sizeof(tcg_target_long) >
+        s->frame_end) {
         tcg_abort();
+    }
     ts->mem_offset = s->current_frame_offset;
     ts->mem_reg = s->frame_reg;
     ts->mem_allocated = 1;
-    s->current_frame_offset += sizeof(tcg_target_long);
+    s->current_frame_offset += (tcg_target_long)sizeof(tcg_target_long);
 }