fuse: Block access to folio overlimit

In the Linux kernel, the following vulnerability has been resolved:

fuse: Block access to folio overlimit

syz reported a slab-out-of-bounds Write in fuse_dev_do_write.

When the number of bytes to be retrieved is truncated to the upper limit by fc->max_pages and there is an offset, the oob is triggered.

Add a loop termination condition to prevent overruns.