1 files changed, 39 insertions, 39 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 010d578118d6..df9f1fe5689b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5105,37 +5105,40 @@ out_unlock:
         return retval;
 }
 
-static int sched_read_attr(struct sched_attr __user *uattr,
-                           struct sched_attr *attr,
-                           unsigned int usize)
+/*
+ * Copy the kernel size attribute structure (which might be larger
+ * than what user-space knows about) to user-space.
+ *
+ * Note that all cases are valid: user-space buffer can be larger or
+ * smaller than the kernel-space buffer. The usual case is that both
+ * have the same size.
+ */
+static int
+sched_attr_copy_to_user(struct sched_attr __user *uattr,
+                        struct sched_attr *kattr,
+                        unsigned int usize)
 {
-        int ret;
+        unsigned int ksize = sizeof(*kattr);
 
         if (!access_ok(uattr, usize))
                 return -EFAULT;
 
         /*
-         * If we're handed a smaller struct than we know of,
-         * ensure all the unknown bits are 0 - i.e. old
-         * user-space does not get uncomplete information.
+         * sched_getattr() ABI forwards and backwards compatibility:
+         *
+         * If usize == ksize then we just copy everything to user-space and all is good.
+         *
+         * If usize < ksize then we only copy as much as user-space has space for,
+         * this keeps ABI compatibility as well. We skip the rest.
+         *
+         * If usize > ksize then user-space is using a newer version of the ABI,
+         * which part the kernel doesn't know about. Just ignore it - tooling can
+         * detect the kernel's knowledge of attributes from the attr->size value
+         * which is set to ksize in this case.
          */
-        if (usize < sizeof(*attr)) {
-                unsigned char *addr;
-                unsigned char *end;
+        kattr->size = min(usize, ksize);
 
-                addr = (void *)attr + usize;
-                end  = (void *)attr + sizeof(*attr);
-
-                for (; addr < end; addr++) {
-                        if (*addr)
-                                return -EFBIG;
-                }
-
-                attr->size = usize;
-        }
-
-        ret = copy_to_user(uattr, attr, attr->size);
-        if (ret)
+        if (copy_to_user(uattr, kattr, kattr->size))
                 return -EFAULT;
 
         return 0;
@@ -5145,20 +5148,18 @@ static int sched_read_attr(struct sched_attr __user *uattr,
  * sys_sched_getattr - similar to sched_getparam, but with sched_attr
  * @pid: the pid in question.
  * @uattr: structure containing the extended parameters.
- * @size: sizeof(attr) for fwd/bwd comp.
+ * @usize: sizeof(attr) that user-space knows about, for forwards and backwards compatibility.
  * @flags: for future extension.
  */
 SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
-                unsigned int, size, unsigned int, flags)
+                unsigned int, usize, unsigned int, flags)
 {
-        struct sched_attr attr = {
-                .size = sizeof(struct sched_attr),
-        };
+        struct sched_attr kattr = { };
         struct task_struct *p;
         int retval;
 
-        if (!uattr || pid < 0 || size > PAGE_SIZE ||
-            size < SCHED_ATTR_SIZE_VER0 || flags)
+        if (!uattr || pid < 0 || usize > PAGE_SIZE ||
+            usize < SCHED_ATTR_SIZE_VER0 || flags)
                 return -EINVAL;
 
         rcu_read_lock();
@@ -5171,25 +5172,24 @@ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
         if (retval)
                 goto out_unlock;
 
-        attr.sched_policy = p->policy;
+        kattr.sched_policy = p->policy;
         if (p->sched_reset_on_fork)
-                attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
+                kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
         if (task_has_dl_policy(p))
-                __getparam_dl(p, &attr);
+                __getparam_dl(p, &kattr);
         else if (task_has_rt_policy(p))
-                attr.sched_priority = p->rt_priority;
+                kattr.sched_priority = p->rt_priority;
         else
-                attr.sched_nice = task_nice(p);
+                kattr.sched_nice = task_nice(p);
 
 #ifdef CONFIG_UCLAMP_TASK
-        attr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
-        attr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
+        kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
+        kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
 #endif
 
         rcu_read_unlock();
 
-        retval = sched_read_attr(uattr, &attr, size);
-        return retval;
+        return sched_attr_copy_to_user(uattr, &kattr, usize);
 
 out_unlock:
         rcu_read_unlock();