From 634a81609561f05266e1f625b6f2567c2e0b0419 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 8 Jul 2017 11:26:39 -0400 Subject: [PATCH] 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 Fixes: 67d7ddded322 ("waitid(2): leave copyout of siginfo to syscall itself") Tested-by: Markus Trippelsdorf Signed-off-by: Al Viro --- kernel/exit.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 2bbc23273e2f..608c9775a37b 100644 --- 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); -- 2.20.1