[PATCH] pidns: fix set/getpriority and ioprio_set/get in PRIO_USER mode

[bsegall]

setpriority(PRIO_USER, 0, x) will change the priority of tasks outside
of the current pid namespace. This is in contrast to both the other
modes of setpriority and the example of kill(-1). Fix this. getpriority
and ioprio have the same failure mode, fix them too.

Signed-off-by: Ben Segall <bsegall@xxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
 block/ioprio.c | 6 ++++--
 kernel/sys.c   | 4 ++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/block/ioprio.c b/block/ioprio.c
index 31666c9..cc7800e 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -123,7 +123,8 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
 				break;
 
 			do_each_thread(g, p) {
-				if (!uid_eq(task_uid(p), uid))
+				if (!uid_eq(task_uid(p), uid) ||
+				    !task_pid_vnr(p))
 					continue;
 				ret = set_task_ioprio(p, ioprio);
 				if (ret)
@@ -220,7 +221,8 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
 				break;
 
 			do_each_thread(g, p) {
-				if (!uid_eq(task_uid(p), user->uid))
+				if (!uid_eq(task_uid(p), user->uid) ||
+				    !task_pid_vnr(p))
 					continue;
 				tmpio = get_task_ioprio(p);
 				if (tmpio < 0)
diff --git a/kernel/sys.c b/kernel/sys.c
index fa2f2f6..6af9212 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -222,7 +222,7 @@ SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
 				goto out_unlock;	/* No processes for this user */
 		}
 		do_each_thread(g, p) {
-			if (uid_eq(task_uid(p), uid))
+			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p))
 				error = set_one_prio(p, niceval, error);
 		} while_each_thread(g, p);
 		if (!uid_eq(uid, cred->uid))
@@ -290,7 +290,7 @@ SYSCALL_DEFINE2(getpriority, int, which, int, who)
 				goto out_unlock;	/* No processes for this user */
 		}
 		do_each_thread(g, p) {
-			if (uid_eq(task_uid(p), uid)) {
+			if (uid_eq(task_uid(p), uid) && task_pid_vnr(p)) {
 				niceval = nice_to_rlimit(task_nice(p));
 				if (niceval > retval)
 					retval = niceval;
-- 
2.6.0.rc0.131.gf624c3d

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