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SubjectRe: [PATCH 05/11] UAPI: coda: Don't use internal kernel structs in UAPI
Le mercredi 05 septembre 2018 à 16:55 +0100, David Howells a écrit :
> The size and layout of internal kernel structures may not be relied
> upon outside of the kernel and may even change in a containerised
> environment if a container image is frozen and shifted to another
> machine.
>
> Excise these from Coda's upc_req struct.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Jan Harkes <jaharkes@cs.cmu.edu>
> cc: coda@cs.cmu.edu
> cc: codalist@coda.cs.cmu.edu
> cc: linux-fsdevel@vger.kernel.org
> ---
>
> include/uapi/linux/coda_psdev.h | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/include/uapi/linux/coda_psdev.h b/include/uapi/linux/coda_psdev.h
> index aa6623efd2dd..9c3acde393cd 100644
> --- a/include/uapi/linux/coda_psdev.h
> +++ b/include/uapi/linux/coda_psdev.h
> @@ -10,14 +10,18 @@
>
> /* messages between coda filesystem in kernel and Venus */
> struct upc_req {
> +#ifdef __KERNEL__
> struct list_head uc_chain;
> +#endif
> caddr_t uc_data;
> u_short uc_flags;
> u_short uc_inSize; /* Size is at most 5000 bytes */
> u_short uc_outSize;
> u_short uc_opcode; /* copied from data to save lookup */
> int uc_unique;
> +#ifdef __KERNEL__
> wait_queue_head_t uc_sleep; /* process' wait queue */
> +#endif
> };
>

This structure should not have been exposed to userspace in the first
place: it's unusable by userspace as it is. It was incorrect to have it
outside of #ifdef __KERNEL__ before commit 607ca46e97a1b ...

... and it's not exchanged between kernel and userspace, see
coda_psdev_write():

struct upc_req *req = NULL;

...

if (copy_from_user(req->uc_data, buf, nbytes)) {
req->uc_flags |= CODA_REQ_ABORT;
wake_up(&req->uc_sleep);
retval = -EFAULT;
goto out;
}

Only data, a caddr_t, is read from userspace.

So the structure can be moved back to <linux/coda_psdev.h>.

> #define CODA_REQ_ASYNC 0x1
>

All CODA_REQ_* defines internals to kernel side and not exchanged with userspace.

Please move them back to <linux/coda_psdev.h>

Regards.

--
Yann Droneaud
OPTEYA



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