[lwip-users] dereferenced NULL Pointer

[Andreas Becker]

Hi all,

I was looking into the file contrib/ports/unix/sys_arch.c

In the function: 
sys_arch_mbox_fetch(struct sys_mbox *mbox, void **msg, u32_t timeout)

is the debug-statement

LWIP_DEBUGF(SYS_DEBUG, ("sys_mbox_fetch: mbox %p msg %p\n", (void *)mbox, 
*msg));

But the "msg" pointer can be NULL an so the debug function tries to 
dereference an NULL pointer. This leads to an Segmentation Fault.

In my opinion it is better to ask if "msg" is NULL and then just use another 
debug_statement like:

if (msg != NULL)
{
  LWIP_DEBUGF(SYS_DEBUG, ("sys_mbox_fetch: mbox %p msg %p\n", (void *)mbox,   
  *msg));
}
else
{
  LWIP_DEBUGF(SYS_DEBUG, ("sys_mbox_fetch: mbox %p msg %p\n", (void *)mbox, 
  msg));
}

I hope it's helpfull.

-- 
Dipl.-Ing.(FH) Andreas Becker
Entwicklung