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Mon, 29 Jul 2019 10:56:23 -0700 (PDT) Received: from brauner.io ([162.223.5.124]) by smtp.gmail.com with ESMTPSA id z17sm83874244iol.73.2019.07.29.10.56.22 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 29 Jul 2019 10:56:22 -0700 (PDT) Date: Mon, 29 Jul 2019 19:56:21 +0200 From: Christian Brauner To: Kees Cook Cc: linux-kernel@vger.kernel.org, oleg@redhat.com, torvalds@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, joel@joelfernandes.org, tglx@linutronix.de, tj@kernel.org, dhowells@redhat.com, jannh@google.com, luto@kernel.org, akpm@linux-foundation.org, cyphar@cyphar.com, viro@zeniv.linux.org.uk, kernel-team@android.com Subject: Re: [PATCH v3 1/2] pidfd: add P_PIDFD to waitid() Message-ID: <20190729175620.uwszsvidnb2cmul4@brauner.io> References: <20190727222229.6516-1-christian@brauner.io> <20190727222229.6516-2-christian@brauner.io> <201907290915.8B421306D@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <201907290915.8B421306D@keescook> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 29, 2019 at 09:24:38AM -0700, Kees Cook wrote: > On Sun, Jul 28, 2019 at 12:22:29AM +0200, Christian Brauner wrote: > > diff --git a/kernel/exit.c b/kernel/exit.c > > index a75b6a7f458a..64bb6893a37d 100644 > > --- a/kernel/exit.c > > +++ b/kernel/exit.c > > @@ -1552,6 +1552,23 @@ static long do_wait(struct wait_opts *wo) > > return retval; > > } > > > > +static struct pid *pidfd_get_pid(unsigned int fd) > > +{ > > + struct fd f; > > + struct pid *pid; > > + > > + f = fdget(fd); > > + if (!f.file) > > + return ERR_PTR(-EBADF); > > + > > + pid = pidfd_pid(f.file); > > + if (!IS_ERR(pid)) > > + get_pid(pid); > > + > > + fdput(f); > > + return pid; > > +} > > + > > static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, > > int options, struct rusage *ru) > > { > > @@ -1574,19 +1591,29 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop, > > type = PIDTYPE_PID; > > if (upid <= 0) > > return -EINVAL; > > + > > + pid = find_get_pid(upid); > > break; > > case P_PGID: > > type = PIDTYPE_PGID; > > if (upid <= 0) > > return -EINVAL; > > + > > + pid = find_get_pid(upid); > > + break; > > + case P_PIDFD: > > + type = PIDTYPE_PID; > > + if (upid < 0) > > + return -EINVAL; > > + > > + pid = pidfd_get_pid(upid); > > + if (IS_ERR(pid)) > > + return PTR_ERR(pid); > > I spent some time convincing myself that this early bail out was > correct. It seems this path is only reachable in the EBADF case, so that > makes sense. The other failure modes in this switch all give a NULL pid > so that the final do_wait() returns ECHILD. So, as long as that's > intentional (which I think it is), this all looks fine. :) Yep, it is. I didn't want to refactor that out of do_wait(). :) Thanks! Christian > > Reviewed-by: Kees Cook