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Re: Environment handling broken in /bin/sh with changes to {get,set,put}env()

On Fri, 13 Jul 2007, Andrey Chernov wrote:

On Sun, Jul 08, 2007 at 09:17:27PM +0400, Andrey Chernov wrote:



I found another breakage case not covered by your last getenv() fix.
Take this simple program:

-- a.c ---------------------------------------------------------------
#include <stdlib.h>
extern char **environ;

main () {

static char *nenv[2];

nenv[0] = "PATH=/bin";
nenv[1] = NULL;

  environ = nenv;
  unsetenv("PATH"); or somethig like
  which touch '=' char in nenv[0]

nenv[0][4] = '\0';

-- a.c ---------------------------------------------------------------


As you may see, compiler puts "PATH=/bin" to the program's .rodata
section which is placed to read only memory.

If later you'll modify this single "PATH=/bin" (comes from "nenv" now)
*equals = '\0';
*equals = '=';
core dump happens, which simulated in my simple a.c example by
nenv[0][4] = '\0';

Just run it and got code dump.

FreeBSD 6 will also dump if the length of the value was less than or
equal to "/bin" since it reuses this string.  This will core dump:

nenv[0] = "PATH=/bin";
nenv[1] = NULL;
environ = nenv;
setenv("PATH", "/bin", 1);

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