BACKPORT: signal: support CLONE_PIDFD with pidfd_send_signal

Let pidfd_send_signal() use pidfds retrieved via CLONE_PIDFD.  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 <christian@brauner.io>
Co-developed-by: Jann Horn <jannh@google.com>
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Howells <dhowells@redhat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
(cherry picked from commit 2151ad1b067275730de1b38c7257478cae47d29e)

Conflicts:
        kernel/sys_ni.c

(1. Replaced COND_SYSCALL with cond_syscall.)

Mot-CRs-fixed: (CR)

Bug: 135608568
Test: test program using syscall(__NR_sys_pidfd_open,..) and poll()
Change-Id: I621fe6547397e0e68c560d7da60ef7715deb290c
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-on: https://gerrit.mot.com/1505852
SLTApproved: Slta Waiver
SME-Granted: SME Approvals Granted
Tested-by: Jira Key
Reviewed-by: Wang Wang <wangwang1@mt.com>
Reviewed-by: Yonghui Jia <jiayh2@motorola.com>
Submit-Approved: Jira Key
Reviewed-on: https://gerrit.mot.com/1796160
Reviewed-by: Xiangpo Zhao <zhaoxp3@motorola.com>

diff --git a/kernel/signal.c b/kernel/signal.c
index 0fba758e1505fb9ba491d08a151a5a9fcadee9cd..45b34181a7638e91e37c9499f77a9eab00502092 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3048,7 +3048,6 @@ 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
@@ -3070,6 +3069,14 @@ static bool access_pidfd_pidns(struct pid *pid)
        return true;
 }
 
+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);
+}
+
 static int copy_siginfo_from_user_any(siginfo_t *kinfo, siginfo_t __user *info)
 {
 #ifdef CONFIG_COMPAT
@@ -3120,7 +3127,7 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
                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;
@@ -3159,7 +3166,6 @@ err:
        fdput(f);
        return ret;
 }
-#endif /* CONFIG_PROC_FS */
 
 static int
 do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)

diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index e91b8a5bebf089cefa3ed47ad809c4380b91182e..b5189762d275c431901add0f680da05016e782d5 100644 (file)
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -156,7 +156,6 @@ cond_syscall(compat_sys_io_submit);
 cond_syscall(compat_sys_io_getevents);
 cond_syscall(sys_sysfs);
 cond_syscall(sys_syslog);
-cond_syscall(sys_pidfd_send_signal);
 cond_syscall(sys_process_vm_readv);
 cond_syscall(sys_process_vm_writev);
 cond_syscall(compat_sys_process_vm_readv);