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Biederman" , Tycho Andersen , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] pidfd: change pidfd_send_signal() to respect PIDFD_THREAD Message-ID: <20240208135344.GD19801@redhat.com> References: <20240207114549.GA12697@redhat.com> <20240208-fragt-prospekt-7866333b15f0@brauner> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240208-fragt-prospekt-7866333b15f0@brauner> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 On 02/08, Christian Brauner wrote: > > On Wed, Feb 07, 2024 at 12:45:49PM +0100, Oleg Nesterov wrote: > > + type = (f.file->f_flags & PIDFD_THREAD) ? PIDTYPE_PID : PIDTYPE_TGID; > > + ret = kill_pid_info_type(sig, &kinfo, pid, type); > > If the user doesn't provide siginfo then the kernel fills in the info in > prepare_kill_siginfo() a few lines above. That sets info->si_code to > SI_USER even for the PIDFD_THREAD case. Whenever the info is filled in > by the kernel it's not exactly userspace impersonating anything plus we > know that what we're sending to is a pidfd by the type of the pidfd. So > it feels like we should fill in SI_TKILL here as well? Hmm. Agreed, will do, thanks. But then I think this needs another preparational 1/2 patch. prepare_kill_siginfo() should have a new arg so that do_tkill() could use it too. (offtopic, but may be the "Only allow sending arbitrary signals to yourself" check in pidfd_send_signal() needs another helper, do_rt_sigqueueinfo() does the same check). > I would also suggest we update the obsolete comment on top of > pidfd_send_signal() along the lines of: Ah, indeed, thanks. Oleg.