sched: Make sched_setattr() correctly return -EFBIG

The documented[1] behavior of sched_attr() in the proposed man page text is:

    sched_attr::size must be set to the size of the structure, as in
    sizeof(struct sched_attr), if the provided structure is smaller
    than the kernel structure, any additional fields are assumed
    '0'. If the provided structure is larger than the kernel structure,
    the kernel verifies all additional fields are '0' if not the
    syscall will fail with -E2BIG.

As currently implemented, sched_copy_attr() returns -EFBIG for
for this case, but the logic in sys_sched_setattr() converts that
error to -EFAULT. This patch fixes the behavior.

[1] http://thread.gmane.org/gmane.linux.kernel/1615615/focus=1697760

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/536CEC17.9070903@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 13584f1cccfc88dbb451f0e56854459d29e8f5d3..f2205f02eb7008224037382c73463cc49f110bdc 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3658,8 +3658,9 @@ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
        if (!uattr || pid < 0 || flags)
                return -EINVAL;
 
-       if (sched_copy_attr(uattr, &attr))
-               return -EFAULT;
+       retval = sched_copy_attr(uattr, &attr);
+       if (retval)
+               return retval;
 
        rcu_read_lock();
        retval = -ESRCH;