[ECOS] return value of fdopen in cyg_httpd_process should be checked for validity

[ECOS] return value of fdopen in cyg_httpd_process should be checked for validity

[sandeep]

function cyg_httpd_process in httpd.c , has code like --

 FILE *client;
------- snipped -------
 client = fdopen( client_socket, "r+");

 /* We are really only interested in the first line.
  */
 fgets( request, sizeof(request), client );
...........
...........

If malloc fails (tracing fdopen internals) then client will be set to NULL and
further referencing
of client cause buggy behaviours. So it is clear that a validity check needs to
be done on return value of fdopen before going ahead with using it's return
value. But what should be the action in that failure case?

should one just return from that point? I guess, if we do that, it will make the
requesting browser to fail getting any response for it's request and retrying
will need to be done. Andrew, is that safe enough?

I can send the trivial patch for it, once above issue is settled.

peace
sandeep





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Re: [ECOS] return value of fdopen in cyg_httpd_process should be checked for validity

[Andrew Lunn]

On Wed, Dec 10, 2003 at 04:20:41PM +0530, sandeep wrote:
> function cyg_httpd_process in httpd.c , has code like --
> 
>  FILE *client;
> ------- snipped -------
>  client = fdopen( client_socket, "r+");
> 
>  /* We are really only interested in the first line.
>   */
>  fgets( request, sizeof(request), client );
> ...........
> ...........
> 
> If malloc fails (tracing fdopen internals) then client will be set
> to NULL and further referencing of client cause buggy behaviours. So
> it is clear that a validity check needs to be done on return value
> of fdopen before going ahead with using it's return value. But what
> should be the action in that failure case?  should one just return
> from that point? I guess, if we do that, it will make the requesting
> browser to fail getting any response for it's request and retrying
> will need to be done. Andrew, is that safe enough?
 
Nick is the person to ask, not me. Nick wrote the code. I just added
IPv6 support.

Just returning is not enough. Doing that will result in the leak of a
socket.

        Andrew

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Re: [ECOS] return value of fdopen in cyg_httpd_process should be checked for validity

[Nick Garnett]

Andrew Lunn <andrew@lunn.ch> writes:

> On Wed, Dec 10, 2003 at 04:20:41PM +0530, sandeep wrote:
> > function cyg_httpd_process in httpd.c , has code like --
> > 
> >  FILE *client;
> > ------- snipped -------
> >  client = fdopen( client_socket, "r+");
> > 
> >  /* We are really only interested in the first line.
> >   */
> >  fgets( request, sizeof(request), client );
> > ...........
> > ...........
> > 
> > If malloc fails (tracing fdopen internals) then client will be set
> > to NULL and further referencing of client cause buggy behaviours. So
> > it is clear that a validity check needs to be done on return value
> > of fdopen before going ahead with using it's return value. But what
> > should be the action in that failure case?  should one just return
> > from that point? I guess, if we do that, it will make the requesting
> > browser to fail getting any response for it's request and retrying
> > will need to be done. Andrew, is that safe enough?
>  
> Nick is the person to ask, not me. Nick wrote the code. I just added
> IPv6 support.
> 
> Just returning is not enough. Doing that will result in the leak of a
> socket.

I suspect that the correct thing to do is to send a pre-packaged
response back to the browser saying something like "Server out of
resources". This would have to be done using a plain write() followed
by a close(). It will probably also need to read() the rest of the
request header. All a bit yukky unfortunately.

-- 
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com      The eCos and RedBoot experts


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