Received-SPF: pass (google.com: domain of linux-kernel+bounces-64918-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Date: Wed, 14 Feb 2024 10:06:41 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Tycho Andersen <tycho@tycho.pizza>
Cc: coverity-bot <keescook@chromium.org>,
	Christian Brauner <brauner@kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Peng Zhang <zhangpeng.00@bytedance.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Heiko Carstens <hca@linux.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mateusz Guzik <mjguzik@gmail.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Tycho Andersen <tandersen@netflix.com>,
	Mike Christie <michael.christie@oracle.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	linux-next@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: Coverity: __do_sys_pidfd_send_signal(): UNINIT
Message-ID: <20240214090640.GB14017@redhat.com>
References: <202402131559.B76A34B@keescook>
 <ZcwGua3a9Z8nJXVq@tycho.pizza>
 <20240214090332.GA14017@redhat.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240214090332.GA14017@redhat.com>
User-Agent: Mutt/1.5.24 (2015-08-30)

On 02/14, Oleg Nesterov wrote:
>
> On 02/13, Tycho Andersen wrote:
> >
> > I think this is a false positive, we have:
>
> Agreed,
>
> > That said, a default case wouldn't hurt, and we should fix the first
> > comment anyways, since now we have extensions.
> >
> > I'm happy to send a patch or maybe it's better for Christian to fix it
> > in-tree.
>
> I leave this to you and Christian, whatever you prefer. But perhaps we
> can simplify these checks? Something like below.

forgot about -EINVAL ...

Oleg.

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3876,10 +3876,6 @@ static struct pid *pidfd_to_pid(const struct file *file)
 	return tgid_pidfd_to_pid(file);
 }
 
-#define PIDFD_SEND_SIGNAL_FLAGS                            \
-	(PIDFD_SIGNAL_THREAD | PIDFD_SIGNAL_THREAD_GROUP | \
-	 PIDFD_SIGNAL_PROCESS_GROUP)
-
 /**
  * sys_pidfd_send_signal - Signal a process through a pidfd
  * @pidfd:  file descriptor of the process
@@ -3903,13 +3899,23 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
 	kernel_siginfo_t kinfo;
 	enum pid_type type;
 
-	/* Enforce flags be set to 0 until we add an extension. */
-	if (flags & ~PIDFD_SEND_SIGNAL_FLAGS)
-		return -EINVAL;
-
-	/* Ensure that only a single signal scope determining flag is set. */
-	if (hweight32(flags & PIDFD_SEND_SIGNAL_FLAGS) > 1)
+	switch (flags) {
+	case 0:
+		/* but see the PIDFD_THREAD check below */
+		type = PIDTYPE_TGID;
+		break;
+	case PIDFD_SIGNAL_THREAD:
+		type = PIDTYPE_PID;
+		break;
+	case PIDFD_SIGNAL_THREAD_GROUP:
+		type = PIDTYPE_TGID;
+		break;
+	case PIDFD_SIGNAL_PROCESS_GROUP:
+		type = PIDTYPE_PGID;
+		break;
+	default:
 		return -EINVAL;
+	}
 
 	f = fdget(pidfd);
 	if (!f.file)
@@ -3926,24 +3932,8 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
 	if (!access_pidfd_pidns(pid))
 		goto err;
 
-	switch (flags) {
-	case 0:
-		/* Infer scope from the type of pidfd. */
-		if (f.file->f_flags & PIDFD_THREAD)
-			type = PIDTYPE_PID;
-		else
-			type = PIDTYPE_TGID;
-		break;
-	case PIDFD_SIGNAL_THREAD:
+	if (!flags && (f.file->f_flags & PIDFD_THREAD))
 		type = PIDTYPE_PID;
-		break;
-	case PIDFD_SIGNAL_THREAD_GROUP:
-		type = PIDTYPE_TGID;
-		break;
-	case PIDFD_SIGNAL_PROCESS_GROUP:
-		type = PIDTYPE_PGID;
-		break;
-	}
 
 	if (info) {
 		ret = copy_siginfo_from_user_any(&kinfo, info);