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Re: [PATCH] [GLIBC RFC] clone3: add CLONE3_RESET_SIGHAND
- From: Christian Brauner <christian dot brauner at ubuntu dot com>
- To: Florian Weimer <fweimer at redhat dot com>, Adhemerval Zanella <adhemerval dot zanella at linaro dot org>, libc-alpha at sourceware dot org
- Date: Tue, 8 Oct 2019 16:14:17 +0200
- Subject: Re: [PATCH] [GLIBC RFC] clone3: add CLONE3_RESET_SIGHAND
- References: <20191008134417.16113-1-christian.brauner@ubuntu.com>
On Tue, Oct 08, 2019 at 03:44:17PM +0200, Christian Brauner wrote:
> Reset all signal handlers of the child not set to SIG_IGN to SIG_DFL.
> Mutually exclusive with CLONE_SIGHAND to not disturb other threads
> signal handler.
>
> Questions for glibc before going to send this for review on lkml:
> - Is it sufficient for glibc to get EINVAL when CLONE3_RESET_SIGNALS is
> passed to determine kernel support for it?
> - Do you really want to have only those signals set to SIG_DFL which are
> not SIG_IGN or do you want to enforce _all_ signals are set to
> SIG_DFL even if they are SIG_IGN?
>
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> ---
> include/uapi/linux/sched.h | 3 +++
> kernel/fork.c | 8 +++++++-
> 2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
> index 99335e1f4a27..e3bc43efbbba 100644
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -33,6 +33,9 @@
> #define CLONE_NEWNET 0x40000000 /* New network namespace */
> #define CLONE_IO 0x80000000 /* Clone io context */
>
> +/* Flags for the clone3() syscall */
> +#define CLONE3_RESET_SIGHAND 0x100000000ULL /* Reset any signal handler which is not SIG_IGN or SIG_DFL to SIG_DFL. */
> +
> #ifndef __ASSEMBLY__
> /**
> * struct clone_args - arguments for the clone3 syscall
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 1f6c45f6a734..3bced4a2931e 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1516,6 +1516,9 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
> refcount_set(&sig->count, 1);
> spin_lock_irq(¤t->sighand->siglock);
> memcpy(sig->action, current->sighand->action, sizeof(sig->action));
> + /* Reset all signal handler not set to SIG_IGN to SIG_DFL. */
> + if (clone_flags & CLONE3_RESET_SIGHAND)
> + flush_signal_handlers(tsk, 0);
> spin_unlock_irq(¤t->sighand->siglock);
> return 0;
> }
> @@ -2567,7 +2570,7 @@ static bool clone3_args_valid(const struct kernel_clone_args *kargs)
> * All lower bits of the flag word are taken.
> * Verify that no other unknown flags are passed along.
> */
> - if (kargs->flags & ~CLONE_LEGACY_FLAGS)
> + if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE3_RESET_SIGNALS))
> return false;
>
> /*
> @@ -2577,6 +2580,9 @@ static bool clone3_args_valid(const struct kernel_clone_args *kargs)
> if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
> return false;
>
> + if (kargs->flags & (CLONE_SIGHAND | CLONE3_RESET_SIGHAND))
> + return false;
That obviously should've been:
if ((kargs->flags & (CLONE_SIGHAND | CLONE3_RESET_SIGHAND)) ==
(CLONE_SIGHAND | CLONE3_RESET_SIGHAND))
return false;
but you get the gist.
Thanks!
Christian