From: Kees Cook <keescook@chromium.org>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Michael Schmitz <schmitzmic@gmail.com>,
linux-arch <linux-arch@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>, Oleg Nesterov <oleg@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
alpha <linux-alpha@vger.kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
linux-m68k <linux-m68k@lists.linux-m68k.org>,
Arnd Bergmann <arnd@kernel.org>, Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 6/9] signal: Fold do_group_exit into get_signal fixing io_uring threads
Date: Fri, 25 Jun 2021 20:42:06 -0700 [thread overview]
Message-ID: <202106252038.389B963B6F@keescook> (raw)
In-Reply-To: <874kdn6q87.fsf_-_@disp2133>
On Thu, Jun 24, 2021 at 02:02:16PM -0500, Eric W. Biederman wrote:
>
> Forld do_group_exit into get_signal as it is the last caller.
>
> Move the group_exit logic above the PF_IO_WORKER exit, ensuring
> that if an PF_IO_WORKER catches SIGKILL every thread in
> the thread group will exit not just the the PF_IO_WORKER.
>
> Now that the information is easily available only set PF_SIGNALED
> when it was a signal that caused the exit.
>
> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> ---
> include/linux/sched/task.h | 1 -
> kernel/exit.c | 31 -------------------------------
> kernel/signal.c | 35 +++++++++++++++++++++++++----------
> 3 files changed, 25 insertions(+), 42 deletions(-)
>
> diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
> index ef02be869cf2..45525512e3d0 100644
> --- a/include/linux/sched/task.h
> +++ b/include/linux/sched/task.h
> @@ -77,7 +77,6 @@ static inline void exit_thread(struct task_struct *tsk)
> {
> }
> #endif
> -extern void do_group_exit(int);
>
> extern void exit_files(struct task_struct *);
> extern void exit_itimers(struct signal_struct *);
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 921519d80b56..635f434122b7 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -892,37 +892,6 @@ SYSCALL_DEFINE1(exit, int, error_code)
> do_exit((error_code&0xff)<<8);
> }
>
> -/*
> - * Take down every thread in the group. This is called by fatal signals
> - * as well as by sys_exit_group (below).
> - */
> -void
> -do_group_exit(int exit_code)
> -{
> - struct signal_struct *sig = current->signal;
> -
> - BUG_ON(exit_code & 0x80); /* core dumps don't get here */
> -
> - if (signal_group_exit(sig))
> - exit_code = sig->group_exit_code;
> - else if (!thread_group_empty(current)) {
> - struct sighand_struct *const sighand = current->sighand;
> -
> - spin_lock_irq(&sighand->siglock);
> - if (signal_group_exit(sig))
> - /* Another thread got here before we took the lock. */
> - exit_code = sig->group_exit_code;
> - else {
> - sig->group_exit_code = exit_code;
> - sig->flags = SIGNAL_GROUP_EXIT;
> - zap_other_threads(current);
Oh, now I see it: the "new code" in start_group_exit() is an open-coded
zap_other_threads()? That wasn't clear to me, but makes sense now.
> - }
> - spin_unlock_irq(&sighand->siglock);
> - }
> -
> - do_exit(exit_code);
> - /* NOTREACHED */
> -}
>
> /*
> * this kills every thread in the thread group. Note that any externally
> diff --git a/kernel/signal.c b/kernel/signal.c
> index c79c010ca5f3..95a076af600a 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -2646,6 +2646,7 @@ bool get_signal(struct ksignal *ksig)
> {
> struct sighand_struct *sighand = current->sighand;
> struct signal_struct *signal = current->signal;
> + int exit_code;
> int signr;
>
> if (unlikely(current->task_works))
> @@ -2848,8 +2849,6 @@ bool get_signal(struct ksignal *ksig)
> /*
> * Anything else is fatal, maybe with a core dump.
> */
> - current->flags |= PF_SIGNALED;
> -
> if (sig_kernel_coredump(signr)) {
> if (print_fatal_signals)
> print_fatal_signal(ksig->info.si_signo);
> @@ -2857,14 +2856,33 @@ bool get_signal(struct ksignal *ksig)
> /*
> * If it was able to dump core, this kills all
> * other threads in the group and synchronizes with
> - * their demise. If we lost the race with another
> - * thread getting here, it set group_exit_code
> - * first and our do_group_exit call below will use
> - * that value and ignore the one we pass it.
> + * their demise. If another thread makes it
> + * to do_coredump first, it will set group_exit_code
> + * which will be passed to do_exit.
> */
> do_coredump(&ksig->info);
> }
>
> + /*
> + * Death signals, no core dump.
> + */
> + exit_code = signr;
> + if (signal_group_exit(signal)) {
> + exit_code = signal->group_exit_code;
> + } else {
> + spin_lock_irq(&sighand->siglock);
> + if (signal_group_exit(signal)) {
> + /* Another thread got here before we took the lock. */
> + exit_code = signal->group_exit_code;
> + } else {
> + start_group_exit_locked(signal, exit_code);
And here's the "if we didn't already do start_group_exit(), do it here".
And that state is entirely captured via the SIGNAL_GROUP_EXIT flag.
Cool.
> + }
> + spin_unlock_irq(&sighand->siglock);
> + }
> +
> + if (exit_code & 0x7f)
> + current->flags |= PF_SIGNALED;
> +
> /*
> * PF_IO_WORKER threads will catch and exit on fatal signals
> * themselves. They have cleanup that must be performed, so
> @@ -2873,10 +2891,7 @@ bool get_signal(struct ksignal *ksig)
> if (current->flags & PF_IO_WORKER)
> goto out;
>
> - /*
> - * Death signals, no core dump.
> - */
> - do_group_exit(ksig->info.si_signo);
> + do_exit(exit_code);
> /* NOTREACHED */
> }
> spin_unlock_irq(&sighand->siglock);
> --
> 2.20.1
>
--
Kees Cook
next prev parent reply other threads:[~2021-06-26 3:42 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 20:57 Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads Eric W. Biederman
2021-06-10 22:04 ` Linus Torvalds
2021-06-11 21:39 ` Eric W. Biederman
2021-06-11 23:26 ` Linus Torvalds
2021-06-13 21:54 ` Eric W. Biederman
2021-06-13 22:18 ` Linus Torvalds
2021-06-14 2:05 ` Michael Schmitz
2021-06-14 5:03 ` Michael Schmitz
2021-06-14 16:26 ` Eric W. Biederman
2021-06-14 22:26 ` Michael Schmitz
2021-06-15 19:30 ` Eric W. Biederman
2021-06-15 19:36 ` [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads Eric W. Biederman
2021-06-15 22:02 ` Linus Torvalds
2021-06-16 16:32 ` Eric W. Biederman
2021-06-16 18:29 ` [PATCH 0/2] alpha/ptrace: Improved switch_stack handling Eric W. Biederman
2021-06-16 18:31 ` [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack Eric W. Biederman
2021-06-16 20:00 ` Linus Torvalds
2021-06-16 20:37 ` Linus Torvalds
2021-06-16 20:57 ` Eric W. Biederman
2021-06-16 21:02 ` Al Viro
2021-06-16 21:08 ` Linus Torvalds
2021-06-16 20:42 ` Eric W. Biederman
2021-06-16 20:17 ` Al Viro
2021-06-21 2:01 ` Michael Schmitz
2021-06-21 2:17 ` Linus Torvalds
2021-06-21 3:18 ` Michael Schmitz
2021-06-21 3:37 ` Linus Torvalds
2021-06-21 4:08 ` Michael Schmitz
2021-06-21 3:44 ` Al Viro
2021-06-21 5:31 ` Michael Schmitz
2021-06-21 2:27 ` Al Viro
2021-06-21 3:36 ` Michael Schmitz
2021-06-16 18:32 ` [PATCH 2/2] alpha/ptrace: Add missing switch_stack frames Eric W. Biederman
2021-06-16 20:25 ` Al Viro
2021-06-16 20:28 ` Al Viro
2021-06-16 20:49 ` Eric W. Biederman
2021-06-16 20:54 ` Al Viro
2021-06-16 20:47 ` Eric W. Biederman
2021-06-16 20:55 ` Al Viro
2021-06-16 20:50 ` [PATCH] alpha: Add extra switch_stack frames in exit, exec, and kernel threads Al Viro
2021-06-15 20:56 ` Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads Michael Schmitz
2021-06-16 0:23 ` Finn Thain
2021-06-15 21:58 ` Linus Torvalds
2021-06-16 15:06 ` Eric W. Biederman
2021-06-21 13:54 ` Al Viro
2021-06-21 14:16 ` Al Viro
2021-06-21 16:50 ` Eric W. Biederman
2021-06-21 23:05 ` Al Viro
2021-06-22 16:39 ` Eric W. Biederman
2021-06-21 15:38 ` Linus Torvalds
2021-06-21 18:59 ` Al Viro
2021-06-21 19:22 ` Linus Torvalds
2021-06-21 19:45 ` Al Viro
2021-06-21 23:14 ` Linus Torvalds
2021-06-21 23:23 ` Al Viro
2021-06-21 23:36 ` Linus Torvalds
2021-06-22 21:02 ` Eric W. Biederman
2021-06-22 21:48 ` Michael Schmitz
2021-06-23 5:26 ` Michael Schmitz
2021-06-23 14:36 ` Eric W. Biederman
2021-06-22 0:01 ` Michael Schmitz
2021-06-22 20:04 ` Michael Schmitz
2021-06-22 20:18 ` Al Viro
2021-06-22 21:57 ` Michael Schmitz
2021-06-21 20:03 ` Eric W. Biederman
2021-06-21 23:15 ` Linus Torvalds
2021-06-22 20:52 ` Eric W. Biederman
2021-06-23 0:41 ` Linus Torvalds
2021-06-23 14:33 ` Eric W. Biederman
2021-06-24 18:57 ` [PATCH 0/9] Refactoring exit Eric W. Biederman
2021-06-24 18:59 ` [PATCH 1/9] signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) Eric W. Biederman
2021-06-24 18:59 ` [PATCH 2/9] signal/seccomp: Refactor seccomp signal and coredump generation Eric W. Biederman
2021-06-26 3:17 ` Kees Cook
2021-06-28 19:21 ` Eric W. Biederman
2021-06-28 14:34 ` [signal/seccomp] 3fdd8c68c2: kernel-selftests.seccomp.seccomp_bpf.fail kernel test robot
2021-06-24 19:00 ` [PATCH 3/9] signal/seccomp: Dump core when there is only one live thread Eric W. Biederman
2021-06-26 3:20 ` Kees Cook
2021-06-24 19:01 ` [PATCH 4/9] signal: Factor start_group_exit out of complete_signal Eric W. Biederman
2021-06-24 20:04 ` Linus Torvalds
2021-06-25 8:47 ` kernel test robot
2021-06-26 3:24 ` Kees Cook
2021-06-24 19:01 ` [PATCH 5/9] signal/group_exit: Use start_group_exit in place of do_group_exit Eric W. Biederman
2021-06-26 3:35 ` Kees Cook
2021-06-24 19:02 ` [PATCH 6/9] signal: Fold do_group_exit into get_signal fixing io_uring threads Eric W. Biederman
2021-06-26 3:42 ` Kees Cook [this message]
2021-06-28 19:25 ` Eric W. Biederman
2021-06-24 19:02 ` [PATCH 7/9] signal: Make individual tasks exiting a first class concept Eric W. Biederman
2021-06-24 20:11 ` Linus Torvalds
2021-06-24 21:37 ` Eric W. Biederman
2021-06-24 19:03 ` [PATCH 8/9] signal/task_exit: Use start_task_exit in place of do_exit Eric W. Biederman
2021-06-26 5:56 ` Kees Cook
2021-06-24 19:03 ` [PATCH 9/9] signal: Move PTRACE_EVENT_EXIT into get_signal Eric W. Biederman
2021-06-24 22:45 ` [PATCH 0/9] Refactoring exit Al Viro
2021-06-27 22:13 ` Al Viro
2021-06-27 22:59 ` Michael Schmitz
2021-06-28 7:31 ` Geert Uytterhoeven
2021-06-28 16:20 ` Eric W. Biederman
2021-06-28 17:14 ` Michael Schmitz
2021-06-28 19:17 ` Geert Uytterhoeven
2021-06-28 20:13 ` Michael Schmitz
2021-06-28 21:18 ` Geert Uytterhoeven
2021-06-28 23:42 ` Michael Schmitz
2021-06-29 20:28 ` [CFT][PATCH] exit/bdflush: Remove the deprecated bdflush system call Eric W. Biederman
2021-06-29 21:45 ` Michael Schmitz
2021-06-30 8:24 ` Geert Uytterhoeven
2021-06-30 8:37 ` Arnd Bergmann
2021-06-30 12:30 ` Cyril Hrubis
2021-06-28 19:02 ` [PATCH 0/9] Refactoring exit Eric W. Biederman
2021-06-21 19:24 ` Kernel stack read with PTRACE_EVENT_EXIT and io_uring threads Al Viro
2021-06-21 23:24 ` Michael Schmitz
2021-06-16 7:38 ` Geert Uytterhoeven
2021-06-16 19:40 ` Michael Schmitz
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