[lwip-devel] [task #14261] [lwip-2.0.0] memp underflow and overflow

[Thomas Nittel]

URL:
  <http://savannah.nongnu.org/task/?14261>

                 Summary: [lwip-2.0.0] memp underflow and overflow
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: thomas_nittel
            Submitted on: Fri 02 Dec 2016 10:55:02 PM GMT
                Category: None
         Should Start On: Fri 02 Dec 2016 12:00:00 AM GMT
   Should be Finished on: Fri 02 Dec 2016 12:00:00 AM GMT
                Priority: 5 - Normal
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
                  Effort: 0.00

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Details:

If I use the option MEMP_OVERFLOW_CHECK == 1 an Assertion/Error will be
thrown: "detected memp overflow in pool TCP_PCB" failed in mempc(135) and
"detected memp underflow in pool TCP_PCB" failed in memp.c(162). It originates
from memp.c(306) res. memp.c(307). For sometimes memp is assigned NULL in
memp.c(303). Consequently the following call of
memp_overflow_check_element_overflow() res.
memp_overflow_check_element_underflow() fails. In this case the else branch in
memp.c(337) is taken and the message "memp_malloc: out of memory in pool
TCP_PCB" is output. However, according to
http://lists.gnu.org/archive/html/lwip-users/2011-11/msg00042.html it is
normal that pcbs are run out. 

Therefore memp_overflow_check_element_overflow() res.
memp_overflow_check_element_underflow() should only be called if memp != NULL.
After I had moved memp.c(311) "if (memp != NULL) {" to memp.c(304) the
Assertion/Error vanished. Maybe this is a solution for this problem.




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