Re: Coverity: __do_sys_pidfd_send_signal(): UNINIT

[Oleg Nesterov]

On 02/14, Oleg Nesterov wrote:
>
> On 02/13, Tycho Andersen wrote:
> >
> > I think this is a false positive, we have:
>
> Agreed,
>
> > That said, a default case wouldn't hurt, and we should fix the first
> > comment anyways, since now we have extensions.
> >
> > I'm happy to send a patch or maybe it's better for Christian to fix it
> > in-tree.
>
> I leave this to you and Christian, whatever you prefer. But perhaps we
> can simplify these checks? Something like below.

forgot about -EINVAL ...

Oleg.

--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -3876,10 +3876,6 @@ 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 | \
-        PIDFD_SIGNAL_PROCESS_GROUP)
-
 /**
  * sys_pidfd_send_signal - Signal a process through a pidfd
  * @pidfd:  file descriptor of the process
@@ -3903,13 +3899,23 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
        kernel_siginfo_t kinfo;
        enum pid_type type;
 
-       /* Enforce flags be set to 0 until we add an extension. */
-       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)
+       switch (flags) {
+       case 0:
+               /* but see the PIDFD_THREAD check below */
+               type = PIDTYPE_TGID;
+               break;
+       case PIDFD_SIGNAL_THREAD:
+               type = PIDTYPE_PID;
+               break;
+       case PIDFD_SIGNAL_THREAD_GROUP:
+               type = PIDTYPE_TGID;
+               break;
+       case PIDFD_SIGNAL_PROCESS_GROUP:
+               type = PIDTYPE_PGID;
+               break;
+       default:
                return -EINVAL;
+       }
 
        f = fdget(pidfd);
        if (!f.file)
@@ -3926,24 +3932,8 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig,
        if (!access_pidfd_pidns(pid))
                goto err;
 
-       switch (flags) {
-       case 0:
-               /* Infer scope from the type of pidfd. */
-               if (f.file->f_flags & PIDFD_THREAD)
-                       type = PIDTYPE_PID;
-               else
-                       type = PIDTYPE_TGID;
-               break;
-       case PIDFD_SIGNAL_THREAD:
+       if (!flags && (f.file->f_flags & PIDFD_THREAD))
                type = PIDTYPE_PID;
-               break;
-       case PIDFD_SIGNAL_THREAD_GROUP:
-               type = PIDTYPE_TGID;
-               break;
-       case PIDFD_SIGNAL_PROCESS_GROUP:
-               type = PIDTYPE_PGID;
-               break;
-       }
 
        if (info) {
                ret = copy_siginfo_from_user_any(&kinfo, info);