User has to mmap user_header and user_index vmalloce'd pointers in order to consume events from userspace. Also we do not let any copies of vma on fork().
Signed-off-by: Roman Penyaev <rpeny...@suse.de> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: linux-fsde...@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- fs/eventpoll.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index e42ddf580556..c5db15c5f8b0 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1426,11 +1426,47 @@ static void ep_show_fdinfo(struct seq_file *m, struct file *f) } #endif +static int ep_eventpoll_mmap(struct file *filep, struct vm_area_struct *vma) +{ + struct eventpoll *ep = vma->vm_file->private_data; + size_t size; + int rc; + + if (!ep_polled_by_user(ep)) + return -ENOTSUPP; + + size = vma->vm_end - vma->vm_start; + if (!vma->vm_pgoff && size > ep->header_length) + return -ENXIO; + if (vma->vm_pgoff && ep->header_length != (vma->vm_pgoff << PAGE_SHIFT)) + /* Index ring starts exactly after the header */ + return -ENXIO; + if (vma->vm_pgoff && size > ep->index_length) + return -ENXIO; + + /* + * vm_pgoff is used *only* for indication, what is mapped: user header + * or user index ring. Sizes are checked above. + */ + if (!vma->vm_pgoff) + rc = remap_vmalloc_range_partial(vma, vma->vm_start, + ep->user_header, size); + else + rc = remap_vmalloc_range_partial(vma, vma->vm_start, + ep->user_index, size); + if (likely(!rc)) + /* No copies for forks(), please */ + vma->vm_flags |= VM_DONTCOPY; + + return rc; +} + /* File callbacks that implement the eventpoll file behaviour */ static const struct file_operations eventpoll_fops = { #ifdef CONFIG_PROC_FS .show_fdinfo = ep_show_fdinfo, #endif + .mmap = ep_eventpoll_mmap, .release = ep_eventpoll_release, .poll = ep_eventpoll_poll, .llseek = noop_llseek, -- 2.21.0