[PATCH 1/3] sched: Make sched_setattr() correctly return -EFBIG

[PATCH 1/3] sched: Make sched_setattr() correctly return -EFBIG

[Michael Kerrisk (man-pages)]

From: Michael Kerrisk <mtk.manpages@gmail.com>

The documented[1] behavior of sched_attr() in your 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>
---
 kernel/sched/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 268a45e..6c9ce28 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3650,8 +3650,9 @@ 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;
-- 
1.9.0

Re: [PATCH 1/3] sched: Make sched_setattr() correctly return -EFBIG

[Michael Kerrisk (man-pages)]

Peter,

In the title of this patch, EFBIG should have been E2BIG. Shall
I resubmit a corrected version?

Cheers,

Michael

On 05/09/2014 04:54 PM, Michael Kerrisk (man-pages) wrote:
> From: Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> The documented[1] behavior of sched_attr() in your 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-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  kernel/sched/core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 268a45e..6c9ce28 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3650,8 +3650,9 @@ 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;
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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