[bug #56922] Resource Leak in TCP packet handling in grub, trivial patch

[Manfred Härtel]

URL:
  <https://savannah.gnu.org/bugs/?56922>

                 Summary: Resource Leak in TCP packet handling in grub,
trivial patch
                 Project: GNU GRUB
            Submitted by: mhaertel
            Submitted on: Fri 20 Sep 2019 03:42:22 PM UTC
                Category: Network
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: 
                 Release: Git master
         Reproducibility: Every Time
         Planned Release: None

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Details:

I wrote a grub module which uses the TCP communication functions included in
grub for educating myself. :-)

During stress tests I recognized a resource leak. Naturally, I suspected my
program first, but could not find a reason why this would happen.

Then I got the feeling that the problem has something to do with the list of
unacked outgoing packets in grub, it seems as if some of them do not get
unallocated from memory. I also recognized that the unacked queue for a
certain socket never exceeds the size of 2 packets, even if it should
actually.

While looking through the source code of tcp.c, I think I found the problem
and made a trivial patch (attached).

Without my patch, a new packet is inserted in the link list after
socket->unack_last, but socket->unack_last does not change, so when another
unacked packet comes it is prepended to the same packet in the list as before,
so the packet we inserted before is not in the linked list anymore, and so
never gets unallocated.

The patch seems to solve my problem and I did not recognize any side effects.



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File Attachments:


-------------------------------------------------------
Date: Fri 20 Sep 2019 03:42:22 PM UTC  Name: tcp.c.patch  Size: 374B   By:
mhaertel

<http://savannah.gnu.org/bugs/download.php?file_id=47553>

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