[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240209-stangen-feuerzeug-17c8662854c9@brauner>
Date: Fri, 9 Feb 2024 16:15:18 +0100
From: Christian Brauner <brauner@...nel.org>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Andy Lutomirski <luto@...capital.net>,
"Eric W. Biederman" <ebiederm@...ssion.com>, Tycho Andersen <tycho@...ho.pizza>, linux-api@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] pidfd: change pidfd_send_signal() to respect
PIDFD_THREAD
On Fri, Feb 09, 2024 at 02:06:50PM +0100, Oleg Nesterov wrote:
> 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.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
How do you feel about the following (untested...) addition?
I've played with PIDFD_SIGNAL_PROCESS_GROUP as well but that code is
fairly new to me so I would need some more time.
>From a473512ed8de2e864961f7009e2f20ce4e7a0778 Mon Sep 17 00:00:00 2001
From: Christian Brauner <brauner@...nel.org>
Date: Fri, 9 Feb 2024 15:49:45 +0100
Subject: [PATCH] [RFC] pidfd: allow to override signal scope in
pidfd_send_signal()
Right now we determine the scope of the signal based on the type of
pidfd. There are use-cases where it's useful to override the scope of
the signal. For example in [1]. Add flags to determine the scope of the
signal:
(1) PIDFD_SIGNAL_THREAD: send signal to specific thread
(2) PIDFD_SIGNAL_THREAD_GROUP: send signal to thread-group
I've put off PIDFD_SIGNAL_PROCESS_GROUP for now since I need to stare at
the code a bit longer how this would work.
Link: https://github.com/systemd/systemd/issues/31093 [1]
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
include/uapi/linux/pidfd.h | 4 ++++
kernel/signal.c | 35 ++++++++++++++++++++++++++++-------
2 files changed, 32 insertions(+), 7 deletions(-)
diff --git a/include/uapi/linux/pidfd.h b/include/uapi/linux/pidfd.h
index 2e6461459877..757ed5a668c6 100644
--- a/include/uapi/linux/pidfd.h
+++ b/include/uapi/linux/pidfd.h
@@ -10,4 +10,8 @@
#define PIDFD_NONBLOCK O_NONBLOCK
#define PIDFD_THREAD O_EXCL
+/* Flags for pidfd_send_signal(). */
+#define PIDFD_SIGNAL_THREAD (1UL << 0)
+#define PIDFD_SIGNAL_THREAD_GROUP (1UL << 1)
+
#endif /* _UAPI_LINUX_PIDFD_H */
diff --git a/kernel/signal.c b/kernel/signal.c
index 9578ce17d85d..1d6586964099 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3872,6 +3872,9 @@ static struct pid *pidfd_to_pid(const struct file *file)
return tgid_pidfd_to_pid(file);
}
+#define PIDFD_SEND_SIGNAL_FLAGS \
+ (PIDFD_SIGNAL_THREAD | PIDFD_SIGNAL_THREAD_GROUP)
+
/**
* sys_pidfd_send_signal - Signal a process through a pidfd
* @pidfd: file descriptor of the process
@@ -3889,14 +3892,19 @@ static struct pid *pidfd_to_pid(const struct file *file)
SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
siginfo_t __user *, info, unsigned int, flags)
{
- int ret;
+ int ret, si_code;
struct fd f;
struct pid *pid;
kernel_siginfo_t kinfo;
bool thread;
+ enum pid_type si_scope;
/* Enforce flags be set to 0 until we add an extension. */
- if (flags)
+ if (flags & ~PIDFD_SEND_SIGNAL_FLAGS)
+ return -EINVAL;
+
+ /* Ensure that only a single signal scope determining flag is set. */
+ if (hweight32(flags & PIDFD_SEND_SIGNAL_FLAGS) > 1)
return -EINVAL;
f = fdget(pidfd);
@@ -3914,7 +3922,22 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
if (!access_pidfd_pidns(pid))
goto err;
- thread = f.file->f_flags & PIDFD_THREAD;
+ switch (flags) {
+ case 0:
+ /* Infer scope from the type of pidfd. */
+ thread = (f.file->f_flags & PIDFD_THREAD);
+ si_scope = thread ? PIDTYPE_PID : PIDTYPE_TGID;
+ si_code = thread ? SI_TKILL : SI_USER;
+ break;
+ case PIDFD_SIGNAL_THREAD:
+ si_scope = PIDTYPE_PID;
+ si_code = SI_TKILL;
+ break;
+ case PIDFD_SIGNAL_THREAD_GROUP:
+ si_scope = PIDTYPE_TGID;
+ si_code = SI_USER;
+ break;
+ }
if (info) {
ret = copy_siginfo_from_user_any(&kinfo, info);
@@ -3931,12 +3954,10 @@ 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,
- thread ? SI_TKILL : SI_USER);
+ prepare_kill_siginfo(sig, &kinfo, si_code);
}
- ret = kill_pid_info_type(sig, &kinfo, pid,
- thread ? PIDTYPE_PID : PIDTYPE_TGID);
+ ret = kill_pid_info_type(sig, &kinfo, pid, si_scope);
err:
fdput(f);
return ret;
--
2.43.0
Powered by blists - more mailing lists