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pidfd: change pidfd_send_signal() to respect PIDFD_THREAD

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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: Tycho Andersen <tandersen@netflix.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20240209130650.GA8048@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Oleg Nesterov 2024-02-09 14:06:50 +01:00 committed by Christian Brauner
parent c044a95026
commit 81b9d8ac06
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 23 additions and 18 deletions
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2
kernel/fork.c
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@ -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) {

39
kernel/signal.c
View File

@ -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;