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[Bug libmudflap/24619] New: mudflap instrumentation of dlopen is incorrect

[forwarded from]

bug submitter writes:

If mudflap is used to instrument a program using dlopen, and the program
(assuming it is compiled with -rdynamic) loads itself by passing NULL for the
path to dlopen, the program will crash unconditionally; that is, regardless of
the options passed to mudflap, so long as instrumentation is enabled.

This is because (at least with GNU/Linux) it is valid to pass a NULL pointer as
the path argument to dlopen, and the instrumentation code unconditionally uses
strlen on that pointer, without checking first if it is NULL.

I have included the following patch, which may help fix the problem.  I have
tested it, but it should work.  As always, it is "as is", with no warranty of
any kind.  The patch is against svn HEAD (r104588).

- --- mf-hooks2.c.orig  2005-10-30 20:35:44.000000000 +0000
+++ mf-hooks2.c 2005-10-30 20:37:38.000000000 +0000
@@ -1679,8 +1679,10 @@ WRAPPER2(void *, dlopen, const char *pat
   void *p;
   size_t n;
   TRACE ("%s\n", __PRETTY_FUNCTION__);
- -  n = strlen (path);
- -  MF_VALIDATE_EXTENT (path, CLAMPADD(n, 1), __MF_CHECK_READ, "dlopen path");
+  if (NULL != path) {
+    n = strlen (path);
+    MF_VALIDATE_EXTENT (path, CLAMPADD(n, 1), __MF_CHECK_READ, "dlopen path");
+  }
   p = dlopen (path, flags);
   if (NULL != p) {
 #ifdef MF_REGISTER_dlopen

           Summary: mudflap instrumentation of dlopen is incorrect
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libmudflap
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: debian-gcc at lists dot debian dot org

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