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[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
- Cc: Christian Brauner <christian dot brauner at ubuntu dot com>
- Date: Tue, 8 Oct 2019 15:44:17 +0200
- Subject: [PATCH] [GLIBC RFC] clone3: add CLONE3_RESET_SIGHAND
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;
+
if ((kargs->flags & (CLONE_THREAD | CLONE_PARENT)) &&
kargs->exit_signal)
return false;
--
2.23.0