Let pidfd_send_signal() use pidfds retrieved via pidctl(). With this patch
pidfd_send_signal() becomes independent of procfs. This fullfils the
request made when we merged the pidfd_send_signal() patchset. The
pidfd_send_signal() syscall is now always available allowing for it to be
used by users without procfs mounted or even users without procfs support
compiled into the kernel.
Signed-off-by: Christian Brauner <christ...@brauner.io>
Reviewed-by: David Howells <dhowe...@redhat.com>
Acked-by: Serge Hallyn <se...@hallyn.com>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: "Eric W. Biederman" <ebied...@xmission.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Alexey Dobriyan <adobri...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Jann Horn <ja...@google.com
Cc: "Michael Kerrisk (man-pages)" <mtk.manpa...@gmail.com>
Cc: Konstantin Khlebnikov <khlebni...@yandex-team.ru>
Cc: Jonathan Kowalski <bl0pbl...@gmail.com>
Cc: "Dmitry V. Levin" <l...@altlinux.org>
Cc: Andy Lutomirsky <l...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Nagarathnam Muthusamy <nagarathnam.muthus...@oracle.com>
Cc: Aleksa Sarai <cyp...@cyphar.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
---
/* changelog */
v1:
- Jann Horn <ja...@google.com> in [1]:
- make access_pidfd_pidns() more readable
---
kernel/signal.c | 29 ++++++++++++-----------------
kernel/sys_ni.c | 3 ---
2 files changed, 12 insertions(+), 20 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index b7953934aa99..7bdeda8333c8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3513,26 +3513,14 @@ SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
return kill_something_info(sig, &info, pid);
}
-#ifdef CONFIG_PROC_FS
/*
* Verify that the signaler and signalee either are in the same pid namespace
* or that the signaler's pid namespace is an ancestor of the signalee's pid
* namespace.
*/
-static bool access_pidfd_pidns(struct pid *pid)
+static inline bool access_pidfd_pidns(struct pid *pid)
{
- struct pid_namespace *active = task_active_pid_ns(current);
- struct pid_namespace *p = ns_of_pid(pid);
-
- for (;;) {
- if (!p)
- return false;
- if (p == active)
- break;
- p = p->parent;
- }
-
- return true;
+ return pidnscmp(task_active_pid_ns(current), ns_of_pid(pid)) >= 0;
}
static int copy_siginfo_from_user_any(kernel_siginfo_t *kinfo, siginfo_t *info)
@@ -3550,6 +3538,14 @@ static int copy_siginfo_from_user_any(kernel_siginfo_t
*kinfo, siginfo_t *info)
return copy_siginfo_from_user(kinfo, info);
}
+static struct pid *pidfd_to_pid(const struct file *file)
+{
+ if (file->f_op == &pidfd_fops)
+ return file->private_data;
+
+ return tgid_pidfd_to_pid(file);
+}
+
/**
* sys_pidfd_send_signal - send a signal to a process through a task file
* descriptor
@@ -3581,12 +3577,12 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
if (flags)
return -EINVAL;
- f = fdget_raw(pidfd);
+ f = fdget(pidfd);
if (!f.file)
return -EBADF;
/* Is this a pidfd? */
- pid = tgid_pidfd_to_pid(f.file);
+ pid = pidfd_to_pid(f.file);
if (IS_ERR(pid)) {
ret = PTR_ERR(pid);
goto err;
@@ -3625,7 +3621,6 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
fdput(f);
return ret;
}
-#endif /* CONFIG_PROC_FS */
static int
do_send_specific(pid_t tgid, pid_t pid, int sig, struct kernel_siginfo *info)
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index d21f4befaea4..4d9ae5ea6caf 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -167,9 +167,6 @@ COND_SYSCALL(syslog);
/* kernel/sched/core.c */
-/* kernel/signal.c */
-COND_SYSCALL(pidfd_send_signal);
-
/* kernel/sys.c */
COND_SYSCALL(setregid);
COND_SYSCALL(setgid);
--
2.21.0
