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Date: Thu, 13 Oct 2011 12:42:42 +0530
From: Huzaifa Sidhpurwala <>
CC: Vasiliy Kulikov <>
Subject: Re: radvd 1.8.2 released with security fixes

On 10/07/2011 04:22 AM, Solar Designer wrote:

> 3) The radvd daemon would not fail on privsep_init() errors, which could
> cause it to run with full root privileges when it should be running as
> an unprivileged user. (CVE-2011-3603)

I think this is not an issue at all:

If you look at the unpatched code, in privsep-linux.c, privsep_init() 
can return -1 at two places.

A. if pipe(pipefds) fails
B. If fork() fails

If either of these functions fails, the end result is that there is no 
fork() and radvd runs as a single process.

Now looking at radvd.c

         /* drop root privileges if requested. */
         if (username) {
                 if (!singleprocess) {
                         dlog(LOG_DEBUG, 3, "Initializing privsep");
                         if (privsep_init() < 0)
                                 flog(LOG_WARNING, "Failed to initialize 

                 if (drop_root_privileges(username) < 0) {

After running privsep_init(), drop_root_privileges() is run, so :

a. if privsep_init() failed and drop_root_privileges() did not fail, you 
end up running a single radvd process running as radvd user, which is 
similar to running "radvd --singleprocess"

b. if privsep_init() failed and drop_root_privileges() failed, you bail 
out of the program, similar to what would happen if privsep_init() did 
not fail.

c. if privsep_init() and drop_root_privileges() did not fail, we have 
two radvd process, one running as radvd user and the other is root

So from what i can see, the maximum harm which would occur if 
privsep_init() fails, is that radvd would effectively run in 
--singleprocess mode

Huzaifa Sidhpurwala / Red Hat Security Response Team

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