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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id v129sm7662740pfc.31.2021.06.25.22.56.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jun 2021 22:56:22 -0700 (PDT) Date: Fri, 25 Jun 2021 22:56:21 -0700 From: Kees Cook To: "Eric W. Biederman" Cc: Linus Torvalds , Al Viro , Michael Schmitz , linux-arch , Jens Axboe , Oleg Nesterov , Linux Kernel Mailing List , Richard Henderson , Ivan Kokshaysky , Matt Turner , alpha , Geert Uytterhoeven , linux-m68k , Arnd Bergmann , Tejun Heo Subject: Re: [PATCH 8/9] signal/task_exit: Use start_task_exit in place of do_exit Message-ID: <202106252255.32CE2711@keescook> References: <87a6njf0ia.fsf@disp2133> <87tulpbp19.fsf@disp2133> <87zgvgabw1.fsf@disp2133> <875yy3850g.fsf_-_@disp2133> <87pmwb5blu.fsf_-_@disp2133> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87pmwb5blu.fsf_-_@disp2133> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 24, 2021 at 02:03:25PM -0500, Eric W. Biederman wrote: > > Reuse start_task_exit_locked to implement start_task_exit. > > Simplify the exit logic by having all exits go through get_signal. > This simplifies the analysis of syncrhonization during exit and > gurantees a full set of registers will be available for ptrace to > examine at PTRACE_EVENT_EXIT. > > Signed-off-by: "Eric W. Biederman" > --- > include/linux/sched/signal.h | 1 + > kernel/exit.c | 4 +++- > kernel/seccomp.c | 2 +- > kernel/signal.c | 12 ++++++++++++ > 4 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h > index a958381ba4a9..3f4e69c019b7 100644 > --- a/include/linux/sched/signal.h > +++ b/include/linux/sched/signal.h > @@ -430,6 +430,7 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume) > > void start_group_exit(int exit_code); > void start_task_exit_locked(struct task_struct *task, int exit_code); > +void start_task_exit(int exit_code); > > void task_join_group_stop(struct task_struct *task); > > diff --git a/kernel/exit.c b/kernel/exit.c > index 635f434122b7..51e0c82b3f7d 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -889,7 +889,9 @@ EXPORT_SYMBOL(complete_and_exit); > > SYSCALL_DEFINE1(exit, int, error_code) > { > - do_exit((error_code&0xff)<<8); > + start_task_exit((error_code&0xff)<<8); > + /* get_signal will call do_exit */ > + return 0; > } > > > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > index b1c06fd1b205..e0c4c123a8bf 100644 > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -1248,7 +1248,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, > force_sig_seccomp(this_syscall, data, true); > } else { > if (action == SECCOMP_RET_KILL_THREAD) > - do_exit(SIGSYS); > + start_task_exit(SIGSYS); > else > start_group_exit(SIGSYS); > } Looks good, yeah. > diff --git a/kernel/signal.c b/kernel/signal.c > index afbc001220dd..63fda9b6bbf9 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1424,6 +1424,18 @@ void start_task_exit_locked(struct task_struct *task, int exit_code) > } > } > > +void start_task_exit(int exit_code) > +{ > + struct task_struct *task = current; > + if (!fatal_signal_pending(task)) { > + struct sighand_struct *const sighand = task->sighand; > + spin_lock_irq(&sighand->siglock); > + if (!fatal_signal_pending(current)) efficiency nit: "task" instead of "current" here, yes? > + start_task_exit_locked(task, exit_code); > + spin_unlock_irq(&sighand->siglock); > + } > +} > + > struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, > unsigned long *flags) > { > -- > 2.20.1 > -- Kees Cook