block: Fix sys_ioprio_set(.which=IOPRIO_WHO_PGRP) task iteration
do_each_pid_thread() { } while_each_pid_thread() is a double loop and
thus break doesn't work as expected. Also, it should be used under
tasklist_lock because otherwise we can race against change_pid() for
PGID/SID.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/YG7Q5C4Rb5dx5GFx@hirez.programming.kicks-ass.net
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/block/ioprio.c b/block/ioprio.c
index 364d229..bee628f 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -119,11 +119,17 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
pgrp = task_pgrp(current);
else
pgrp = find_vpid(who);
+
+ read_lock(&tasklist_lock);
do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
ret = set_task_ioprio(p, ioprio);
- if (ret)
- break;
+ if (ret) {
+ read_unlock(&tasklist_lock);
+ goto out;
+ }
} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
+ read_unlock(&tasklist_lock);
+
break;
case IOPRIO_WHO_USER:
uid = make_kuid(current_user_ns(), who);
@@ -153,6 +159,7 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
ret = -EINVAL;
}
+out:
rcu_read_unlock();
return ret;
}
