From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Jones Subject: Re: [PATCH] Fix buffer overflow in output() when pid slot is not found Date: Fri, 23 May 2014 20:51:02 -0400 Message-ID: <20140524005102.GB7139@redhat.com> References: <1400836143-22355-1-git-send-email-mpe@ellerman.id.au> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <1400836143-22355-1-git-send-email-mpe@ellerman.id.au> Sender: trinity-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Michael Ellerman Cc: trinity@vger.kernel.org On Fri, May 23, 2014 at 07:09:03PM +1000, Michael Ellerman wrote: > In output() we sprintf() the result of find_pid_slot(). We print the pid > slot to the buffer with %u and have space for two digits of pid slot. > find_pid_slot() potentially returns PIDSLOT_NOT_FOUND (-1), which when > printed with %u is 4294967295 - ten digits. > > Fix it two ways, use snprintf() - truncated output is better than a > buffer overflow. And allocate more space in the buffer, 32 bytes is a > nice round size, and gives us space for everything. heh, this has been nagging me from time to time, but it wasn't a problem until recently. I'm curious why you're hitting that PIDSLOT_NOT_FOUND case though, as it's a "should never happen" case. Anyway, it's the right thing to do, so I pushed this out. > @@ -311,7 +311,7 @@ void output(unsigned char level, const char *fmt, ...) > unsigned int slot; > > slot = find_pid_slot(pid); > - sprintf(child_prefix, "[child%u:%u]", slot, pid); > + snprintf(child_prefix, sizeof(child_prefix), "[child%u:%u]", slot, pid); > prefix = child_prefix; might be worth it to add something later to print PIDSLOT_NOT_FOUND entries as '?' rather than 4294967295. thanks, Dave