userfaultfd: require UFFDIO_API before other ioctls

UFFDIO_API was already forced before read/poll could work.  This makes the
code more strict to force it also for all other ioctls.

All users would already have been required to call UFFDIO_API before
invoking other ioctls but this makes it more explicit.

This will ensure we can change all ioctls (all but UFFDIO_API/struct
uffdio_api) with a bump of uffdio_api.api.

There's no actual plan or need to change the API or the ioctl, the current
API already should cover fine even the non cooperative usage, but this is
just for the longer term future just in case.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 5f11678907d5d90427f089a3c0e649c4ee2444d1..af88ef6fffff7e972fcee7a26032424b4318dbb7 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -577,7 +577,6 @@ static ssize_t userfaultfd_read(struct file *file, char __user *buf,
 
        if (ctx->state == UFFD_STATE_WAIT_API)
                return -EINVAL;
-       BUG_ON(ctx->state != UFFD_STATE_RUNNING);
 
        for (;;) {
                if (count < sizeof(msg))
@@ -1115,6 +1114,9 @@ static long userfaultfd_ioctl(struct file *file, unsigned cmd,
        int ret = -EINVAL;
        struct userfaultfd_ctx *ctx = file->private_data;
 
+       if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
+               return -EINVAL;
+
        switch(cmd) {
        case UFFDIO_API:
                ret = userfaultfd_api(ctx, arg);