tvac: fix segfault on DMSYMLINK or DMDEVICE - plan9port - [fork] Plan 9 from user space
git clone git://src.adamsgaard.dk/plan9port
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---
commit 68e24566b6ba442b2bdba2dfc111c5a0d333cc42
parent 258cfab2fe5a816f23723f696c53ad6e61f6b501
Author: David du Colombier <0intro@gmail.com>
Date:   Mon, 16 Jan 2012 17:06:41 -0500

vac: fix segfault on DMSYMLINK or DMDEVICE

Fix segfault when the first archived file is DMSYMLINK or DMDEVICE.
Reinitialize the buffer to zero before calling readlink.

R=rsc
CC=plan9port.codebot
http://codereview.appspot.com/5500097

Diffstat:
  M src/cmd/vac/vac.c                   |      10 ++++++----

1 file changed, 6 insertions(+), 4 deletions(-)
---
diff --git a/src/cmd/vac/vac.c b/src/cmd/vac/vac.c
t@@ -501,12 +501,17 @@ vac(VacFile *fp, VacFile *diffp, char *name, Dir *d)
 
         if(vacfilesetdir(f, &vd) < 0)
                 warn("vacfilesetdir %s: %r", name);
-        
+
+        bsize = fs->bsize;
+        if(buf == nil)
+                buf = vtmallocz(bsize);
+
 #ifdef PLAN9PORT
         if(d->mode&(DMSOCKET|DMNAMEDPIPE)){
                 /* don't write anything */
         }
         else if(d->mode&DMSYMLINK){
+                memset(buf, 0, sizeof buf);
                 n = readlink(name, buf, sizeof buf);
                 if(n > 0 && vacfilewrite(f, buf, n, 0) < 0){
                         warn("venti write %s: %r", name);
t@@ -539,9 +544,6 @@ vac(VacFile *fp, VacFile *diffp, char *name, Dir *d)
                 }
         }else{
                 off = 0;
-                bsize = fs->bsize;
-                if(buf == nil)
-                        buf = vtmallocz(bsize);
                 if(fdiff){
                         /*
                          * Copy fdiff's contents into f by moving the score.