Unverified Commit 81b9d8ac authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Christian Brauner
Browse files

pidfd: change pidfd_send_signal() to respect PIDFD_THREAD 



Turn kill_pid_info() into kill_pid_info_type(), this allows to pass any
pid_type to group_send_sig_info(), despite its name it should work fine
even if type = PIDTYPE_PID.

Change pidfd_send_signal() to use PIDTYPE_PID or PIDTYPE_TGID depending
on PIDFD_THREAD.

While at it kill another TODO comment in pidfd_show_fdinfo(). As Christian
expains fdinfo reports f_flags, userspace can already detect PIDFD_THREAD.

Reviewed-by: default avatarTycho Andersen <tandersen@netflix.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240209130650.GA8048@redhat.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent c044a950

kernel/fork.c

+0 −2
Original line number Diff line number Diff line
@@ -2051,8 +2051,6 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) 


	seq_put_decimal_ll(m, "Pid:\t", nr);



	/* TODO: report PIDFD_THREAD */



#ifdef CONFIG_PID_NS

	seq_put_decimal_ll(m, "\nNSpid:\t", nr);

	if (nr > 0) {

kernel/signal.c

+23 −16
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <linux/cgroup.h>

#include <linux/audit.h>

#include <linux/sysctl.h>

#include <uapi/linux/pidfd.h>



#define CREATE_TRACE_POINTS

#include <trace/events/signal.h>
@@ -1436,7 +1437,8 @@ void lockdep_assert_task_sighand_held(struct task_struct *task) 
#endif



/*

 * send signal info to all the members of a group

 * send signal info to all the members of a thread group or to the

 * individual thread if type == PIDTYPE_PID.

 */

int group_send_sig_info(int sig, struct kernel_siginfo *info,

			struct task_struct *p, enum pid_type type)
@@ -1478,7 +1480,8 @@ int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp) 
	return ret;

}



int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)

static int kill_pid_info_type(int sig, struct kernel_siginfo *info,

				struct pid *pid, enum pid_type type)

{

	int error = -ESRCH;

	struct task_struct *p;
@@ -1487,11 +1490,10 @@ int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid) 
		rcu_read_lock();

		p = pid_task(pid, PIDTYPE_PID);

		if (p)

			error = group_send_sig_info(sig, info, p, PIDTYPE_TGID);

			error = group_send_sig_info(sig, info, p, type);

		rcu_read_unlock();

		if (likely(!p || error != -ESRCH))

			return error;



		/*

		 * The task was unhashed in between, try again.  If it

		 * is dead, pid_task() will return NULL, if we race with
@@ -1500,6 +1502,11 @@ int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid) 
	}

}



int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)

{

	return kill_pid_info_type(sig, info, pid, PIDTYPE_TGID);

}



static int kill_proc_info(int sig, struct kernel_siginfo *info, pid_t pid)

{

	int error;
@@ -3873,14 +3880,10 @@ static struct pid *pidfd_to_pid(const struct file *file) 
 * @info:   signal info

 * @flags:  future flags

 *

 * The syscall currently only signals via PIDTYPE_PID which covers

 * kill(<positive-pid>, <signal>. It does not signal threads or process

 * groups.

 * In order to extend the syscall to threads and process groups the @flags

 * argument should be used. In essence, the @flags argument will determine

 * what is signaled and not the file descriptor itself. Put in other words,

 * grouping is a property of the flags argument not a property of the file

 * descriptor.

 * Send the signal to the thread group or to the individual thread depending

 * on PIDFD_THREAD.

 * In the future extension to @flags may be used to override the default scope

 * of @pidfd.

 *

 * Return: 0 on success, negative errno on failure

 */
@@ -3891,6 +3894,7 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, 
	struct fd f;

	struct pid *pid;

	kernel_siginfo_t kinfo;

	enum pid_type type;



	/* Enforce flags be set to 0 until we add an extension. */

	if (flags)
@@ -3911,6 +3915,11 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, 
	if (!access_pidfd_pidns(pid))

		goto err;



	if (f.file->f_flags & PIDFD_THREAD)

		type = PIDTYPE_PID;

	else

		type = PIDTYPE_TGID;



	if (info) {

		ret = copy_siginfo_from_user_any(&kinfo, info);

		if (unlikely(ret))
@@ -3926,12 +3935,10 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, 
		    (kinfo.si_code >= 0 || kinfo.si_code == SI_TKILL))

			goto err;

	} else {

		prepare_kill_siginfo(sig, &kinfo, PIDTYPE_TGID);

		prepare_kill_siginfo(sig, &kinfo, type);

	}



	/* TODO: respect PIDFD_THREAD */

	ret = kill_pid_info(sig, &kinfo, pid);



	ret = kill_pid_info_type(sig, &kinfo, pid, type);

err:

	fdput(f);

	return ret;