UBUNTU: SAUCE: Revert "UBUNTU: SAUCE: bpf: prevent writable memory-mapping of read...

[mirror_ubuntu-hirsute-kernel.git] / kernel / bpf / ringbuf.c

diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index d71c54c37efd9cc66b3601d19553eaf6903089a2..b86d80c9cd59b0009b14c456a32d4d950ec418a5 100644 (file)
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c
@@ -221,20 +221,25 @@ static int ringbuf_map_get_next_key(struct bpf_map *map, void *key,
        return -ENOTSUPP;
 }
 
+static size_t bpf_ringbuf_mmap_page_cnt(const struct bpf_ringbuf *rb)
+{
+       size_t data_pages = (rb->mask + 1) >> PAGE_SHIFT;
+
+       /* consumer page + producer page + 2 x data pages */
+       return RINGBUF_POS_PAGES + 2 * data_pages;
+}
+
 static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma)
 {
        struct bpf_ringbuf_map *rb_map;
+       size_t mmap_sz;
 
        rb_map = container_of(map, struct bpf_ringbuf_map, map);
+       mmap_sz = bpf_ringbuf_mmap_page_cnt(rb_map->rb) << PAGE_SHIFT;
 
-       if (vma->vm_flags & VM_WRITE)
-               /* allow writable mapping for the consumer_pos only */
-               if (vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != PAGE_SIZE)
-                       return -EPERM;
-       else
-               vma->vm_flags &= ~VM_MAYWRITE;
+       if (vma->vm_pgoff * PAGE_SIZE + (vma->vm_end - vma->vm_start) > mmap_sz)
+               return -EINVAL;
 
-               /* remap_vmalloc_range() checks size and offset constraints */
        return remap_vmalloc_range(vma, rb_map->rb,
                                   vma->vm_pgoff + RINGBUF_PGOFF);
 }