fix waitid(2) breakage

We lose the distinction between "found a PID" and "nothing, but that's not
an error" a bit too early in waitid().  Easily fixed, fortunately...

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Fixes: 67d7ddded322 ("waitid(2): leave copyout of siginfo to syscall itself")
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/kernel/exit.c b/kernel/exit.c
index 2bbc23273e2fe664d15f4bf940366ebaede55009..608c9775a37bc9022759f60e54b1dfcc0c6522d7 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1590,9 +1590,6 @@ static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
        wo.wo_rusage    = ru;
        ret = do_wait(&wo);
 
-       if (ret > 0)
-               ret = 0;
-
        put_pid(pid);
        return ret;
 }
@@ -1603,6 +1600,11 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
        struct rusage r;
        struct waitid_info info = {.status = 0};
        long err = kernel_waitid(which, upid, &info, options, ru ? &r : NULL);
+       int signo = 0;
+       if (err > 0) {
+               signo = SIGCHLD;
+               err = 0;
+       }
 
        if (!err) {
                if (ru && copy_to_user(ru, &r, sizeof(struct rusage)))
@@ -1612,7 +1614,7 @@ SYSCALL_DEFINE5(waitid, int, which, pid_t, upid, struct siginfo __user *,
                return err;
 
        user_access_begin();
-       unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+       unsafe_put_user(signo, &infop->si_signo, Efault);
        unsafe_put_user(0, &infop->si_errno, Efault);
        unsafe_put_user((short)info.cause, &infop->si_code, Efault);
        unsafe_put_user(info.pid, &infop->si_pid, Efault);
@@ -1714,6 +1716,11 @@ COMPAT_SYSCALL_DEFINE5(waitid,
        struct rusage ru;
        struct waitid_info info = {.status = 0};
        long err = kernel_waitid(which, pid, &info, options, uru ? &ru : NULL);
+       int signo = 0;
+       if (err > 0) {
+               signo = SIGCHLD;
+               err = 0;
+       }
 
        if (!err && uru) {
                /* kernel_waitid() overwrites everything in ru */
@@ -1729,7 +1736,7 @@ COMPAT_SYSCALL_DEFINE5(waitid,
                return err;
 
        user_access_begin();
-       unsafe_put_user(err ? 0 : SIGCHLD, &infop->si_signo, Efault);
+       unsafe_put_user(signo, &infop->si_signo, Efault);
        unsafe_put_user(0, &infop->si_errno, Efault);
        unsafe_put_user((short)info.cause, &infop->si_code, Efault);
        unsafe_put_user(info.pid, &infop->si_pid, Efault);