Re: Complex config triggering Segfault in pattern matching code.

[Peter Stephenson <p.w.stephenson@ntlworld.com>]

On Wed, 17 Dec 2014 22:14:00 -0800
Bart Schaefer <schaefer@brasslantern.com> wrote:
> This is the one that repeats a lot:
> 
> ==1705==  Uninitialised value was created by a heap allocation
> ==1705==    at 0x4C2C29E: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
> ==1705==    by 0x45C798: zrealloc (mem.c:938)
> ==1705==    by 0x65B0D18: set_region_highlight (zle_refresh.c:454)
> 
> It would appear that the loop at zle_refresh.c:461 needs to assign
> values to rhp->start_meta and rhp->end_meta at the same time that it
> calculates rhp->start and rhp->end.  However, I'm not familiar enough
> with the region_highlight algorithm to be sure how to initialize those.

Zeroing at the realloc should stop this.  Watch carefully in case I've
got the sums wrong.
 
> It's possible that fixing this will fix the next one as a side-effect.
> 
> Finally this one repeats a few times:
> 
> ==1705== Conditional jump or move depends on uninitialised value(s)
> ==1705==    at 0x5A04253: vfprintf (in /usr/lib/libc-2.20.so)
> ==1705==    by 0x5A278FA: vsprintf (in /usr/lib/libc-2.20.so)
> ==1705==    by 0x5A0ACD6: sprintf (in /usr/lib/libc-2.20.so)
> ==1705==    by 0x65B0B66: get_region_highlight (zle_refresh.c:410)
> 
> That's this:
> 
> 	sprintf(digbuf1, "%d", rhp->start);
> 	sprintf(digbuf2, "%d", rhp->end);
> 
> I'm confused about that one because I can't see where rhp->start might
> be coming from without getting initialized.  It LOOKS like the loop in
> set_region_highlight() always either initializes those, or truncates
> the array to be no more than N_SPECIAL_HIGHLIGHTS elements long.  In
> the latter case the loop containing those sprintf's should never make
> a circuit.  There is a potential problem in that the loop test is just
> (arrsize--) which could go on infinitely if arrsize is negative when
> the loop begins, but there isn't enough log output for this to be an
> infinite loop.

I don't see how arrsize could be negative, but here's a debug test.

diff --git a/Src/Zle/zle_refresh.c b/Src/Zle/zle_refresh.c
index 9f80753..d63f9b8 100644
--- a/Src/Zle/zle_refresh.c
+++ b/Src/Zle/zle_refresh.c
@@ -399,6 +399,7 @@ get_region_highlight(UNUSED(Param pm))
     if (!arrsize)
 	return hmkarray(NULL);
     arrsize -= N_SPECIAL_HIGHLIGHTS;
+    DPUTS(arrsize < 0, "arrsize is negative from n_region_highlights");
     arrp = retarr = (char **)zhalloc((arrsize+1)*sizeof(char *));
 
     /* ignore special highlighting */
@@ -450,10 +451,15 @@ set_region_highlight(UNUSED(Param pm), char **aval)
     len = aval ? arrlen(aval) : 0;
     if (n_region_highlights != len + N_SPECIAL_HIGHLIGHTS) {
 	/* no null termination, but include special highlighting at start */
-	n_region_highlights = len + N_SPECIAL_HIGHLIGHTS;
+	int newsize = len + N_SPECIAL_HIGHLIGHTS
+	int diffsize = newsize - n_region_highlights;
 	region_highlights = (struct region_highlight *)
 	    zrealloc(region_highlights,
-		     sizeof(struct region_highlight) * n_region_highlights);
+		     sizeof(struct region_highlight) * newsize);
+	if (diffsize > 0)
+	    memset(region_highlights + newsize, 0,
+		   sizeof(struct region_highlight) * diffsize);
+	n_region_highlights = newsize;
     }
 
     if (!aval)

-- 
Peter Stephenson <p.w.stephenson@ntlworld.com>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/