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Date: Wed, 14 Feb 2024 11:11:55 -0700
From: Tycho Andersen <tycho@tycho.pizza>
To: Oleg Nesterov <oleg@redhat.com>
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: <Zc0Ca5te+QFBZ1U6@tycho.pizza>
References: <202402131559.B76A34B@keescook>
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 <20240214090332.GA14017@redhat.com>
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 <20240214175555.GC16265@redhat.com>
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In-Reply-To: <20240214175555.GC16265@redhat.com>

On Wed, Feb 14, 2024 at 06:55:55PM +0100, Oleg Nesterov wrote:
> Hi Tycho,
> 
> let me repeat just in case, I am fine either way, whatever you and
> Christian prefer. In particular, I agree in advance if you decide
> to not change the current code, it is correct even if it can fool
> the tools.
> 
> That said,
> 
> On 02/14, Tycho Andersen wrote:
> >
> > On Wed, Feb 14, 2024 at 10:06:41AM +0100, Oleg Nesterov wrote:
> > >
> > > -	/* 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 */
> >
> > Why not put that bit inline?
> 
> Not sure I understand what does "inline" mean... but let me reply
> anyway.
> 
> We want to check the "flags" argument at the start, we do not want to
> delay the "case 0:" check until we have f.file (so that we can check
> f.file->f_flags).

Fair point. I was thinking delaying it would make it simpler, but then
you have to free the file and it's less fast in the EINVAL case. I
also don't have a strong opinion here.

Tycho