wait_noreap_copyout(): check for ->wo_info != NULL

Current behaviour of sys_waitid() looks odd.  If user passes infop ==
NULL, sys_waitid() returns success.  When user additionally specifies flag
WNOWAIT, sys_waitid() returns -EFAULT on the same conditions.  When user
combines WNOWAIT with WCONTINUED, sys_waitid() again returns success.

This patch adds check for ->wo_info in wait_noreap_copyout().

User-visible change: starting from this commit, sys_waitid() always checks
infop != NULL and does not fail if it is NULL.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 12 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 2cc69eb8db2..6c75ff83a8f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1140,18 +1140,20 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
 
         put_task_struct(p);
         infop = wo->wo_info;
-        if (!retval)
-                retval = put_user(SIGCHLD, &infop->si_signo);
-        if (!retval)
-                retval = put_user(0, &infop->si_errno);
-        if (!retval)
-                retval = put_user((short)why, &infop->si_code);
-        if (!retval)
-                retval = put_user(pid, &infop->si_pid);
-        if (!retval)
-                retval = put_user(uid, &infop->si_uid);
-        if (!retval)
-                retval = put_user(status, &infop->si_status);
+        if (infop) {
+                if (!retval)
+                        retval = put_user(SIGCHLD, &infop->si_signo);
+                if (!retval)
+                        retval = put_user(0, &infop->si_errno);
+                if (!retval)
+                        retval = put_user((short)why, &infop->si_code);
+                if (!retval)
+                        retval = put_user(pid, &infop->si_pid);
+                if (!retval)
+                        retval = put_user(uid, &infop->si_uid);
+                if (!retval)
+                        retval = put_user(status, &infop->si_status);
+        }
         if (!retval)
                 retval = pid;
         return retval;