Bug in khttpd, kernel 2.4.10 -- khttpd crashing when apache is not running ; corresponding HTTP error message

[Rui Ribeiro]

------ =_NextPart_000_01C14771.B0EC0960
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit

Howdy,

First I would like to say hello to everyone in this list.

I'm running kernel 2.4.10 (Intel), and performing experiments with the 
khttpd server compiled as a module. I am writing to this list concerning a 
couple of things I noticed in khttpd, and offering a fix. If this is 
already a known fact, I didn't find it in the archives.

Problem description:
-----------------------------

I began noticing that it crashed always with a kernel error or hanging the 
machine when apache was not running. When the machine survived, it also 
returned a 403 error,  with a "Permission denied" message.

The hack:
------------------

Upon source investigation, I noticed that at 
/usr/src/linux/net/khttpd/userspace.c, at the function Userspace, in the 
place where's the user-daemon no present case is coded, a structure element 
is not released.

After correction, I have also changed the 403 error (permission denied), to 
a 503 Service Unavailable, as I believe it's more correct. If the khttpd 
daemon can't call Apache (or other userspace daemon) when it's not capable 
of processing the request, it's better to give a 503 message than a 403, 
for  my and the users'  sanity sake.

So, in the  2.4.10 kernel source tree, in the already mentioned 
/usr/src/linux/net/khttpd/userspace.c, at line 114, you can make the 
following changes:

Send403(CurrentRequest->sock); to Send50x(CurrentRequest-sock);

Append the following lines after the Send50x:
sock_release(CurrentRequest->sock);
CurrentRequest->sock=NULL;

A diff file is included as an attachment.

Regards,
--
Rui Ribeiro
Network and Security consultant
http://www.case.pt

P.S. A copy of this message has already been sent to khttpd users list.
------ =_NextPart_000_01C14771.B0EC0960
Content-Type: application/octet-stream; name="userspace.diff"
Content-Transfer-Encoding: base64

MTAxZDEwMA0KPCANCjEwMmExMDINCj4gCQkJDQoxMTMsMTE5YzExMywxMTUNCjwgCQ0KPCAvKiBS
dWkgKi8NCjwgCQkJU2VuZDUweChDdXJyZW50UmVxdWVzdC0+c29jayk7IC8qIFNvcnJ5LCBubyBn
by4uLiAqLw0KPCAJCQlzb2NrX3JlbGVhc2UoQ3VycmVudFJlcXVlc3QtPnNvY2spOw0KPCAJCQlD
dXJyZW50UmVxdWVzdC0+c29jayA9IE5VTEw7CSAvKiBXZSBubyBsb25nZXIgb3duIGl0ICovDQo8
IC8qIEVuZCBSdWkgKi8NCjwgDQotLS0NCj4gCQkJDQo+IAkJCVNlbmQ0MDMoQ3VycmVudFJlcXVl
c3QtPnNvY2spOyAvKiBTb3JyeSwgbm8gZ28uLi4gKi8NCj4gCQkJDQo=

------ =_NextPart_000_01C14771.B0EC0960--