diff options
Diffstat (limited to 'kernel/bpf/ringbuf.c')
| -rw-r--r-- | kernel/bpf/ringbuf.c | 62 |
1 files changed, 56 insertions, 6 deletions
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index b483aea35f41..754e915748fb 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -38,10 +38,27 @@ struct bpf_ringbuf { struct page **pages; int nr_pages; spinlock_t spinlock ____cacheline_aligned_in_smp; - /* Consumer and producer counters are put into separate pages to allow - * mapping consumer page as r/w, but restrict producer page to r/o. - * This protects producer position from being modified by user-space - * application and ruining in-kernel position tracking. + /* Consumer and producer counters are put into separate pages to + * allow each position to be mapped with different permissions. + * This prevents a user-space application from modifying the + * position and ruining in-kernel tracking. The permissions of the + * pages depend on who is producing samples: user-space or the + * kernel. + * + * Kernel-producer + * --------------- + * The producer position and data pages are mapped as r/o in + * userspace. For this approach, bits in the header of samples are + * used to signal to user-space, and to other producers, whether a + * sample is currently being written. + * + * User-space producer + * ------------------- + * Only the page containing the consumer position is mapped r/o in + * user-space. User-space producers also use bits of the header to + * communicate to the kernel, but the kernel must carefully check and + * validate each sample to ensure that they're correctly formatted, and + * fully contained within the ring buffer. */ unsigned long consumer_pos __aligned(PAGE_SIZE); unsigned long producer_pos __aligned(PAGE_SIZE); @@ -224,7 +241,7 @@ static int ringbuf_map_get_next_key(struct bpf_map *map, void *key, return -ENOTSUPP; } -static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma) +static int ringbuf_map_mmap_kern(struct bpf_map *map, struct vm_area_struct *vma) { struct bpf_ringbuf_map *rb_map; @@ -242,6 +259,26 @@ static int ringbuf_map_mmap(struct bpf_map *map, struct vm_area_struct *vma) vma->vm_pgoff + RINGBUF_PGOFF); } +static int ringbuf_map_mmap_user(struct bpf_map *map, struct vm_area_struct *vma) +{ + struct bpf_ringbuf_map *rb_map; + + rb_map = container_of(map, struct bpf_ringbuf_map, map); + + if (vma->vm_flags & VM_WRITE) { + if (vma->vm_pgoff == 0) + /* Disallow writable mappings to the consumer pointer, + * and allow writable mappings to both the producer + * position, and the ring buffer data itself. + */ + return -EPERM; + } else { + vma->vm_flags &= ~VM_MAYWRITE; + } + /* remap_vmalloc_range() checks size and offset constraints */ + return remap_vmalloc_range(vma, rb_map->rb, vma->vm_pgoff + RINGBUF_PGOFF); +} + static unsigned long ringbuf_avail_data_sz(struct bpf_ringbuf *rb) { unsigned long cons_pos, prod_pos; @@ -269,7 +306,7 @@ const struct bpf_map_ops ringbuf_map_ops = { .map_meta_equal = bpf_map_meta_equal, .map_alloc = ringbuf_map_alloc, .map_free = ringbuf_map_free, - .map_mmap = ringbuf_map_mmap, + .map_mmap = ringbuf_map_mmap_kern, .map_poll = ringbuf_map_poll, .map_lookup_elem = ringbuf_map_lookup_elem, .map_update_elem = ringbuf_map_update_elem, @@ -278,6 +315,19 @@ const struct bpf_map_ops ringbuf_map_ops = { .map_btf_id = &ringbuf_map_btf_ids[0], }; +BTF_ID_LIST_SINGLE(user_ringbuf_map_btf_ids, struct, bpf_ringbuf_map) +const struct bpf_map_ops user_ringbuf_map_ops = { + .map_meta_equal = bpf_map_meta_equal, + .map_alloc = ringbuf_map_alloc, + .map_free = ringbuf_map_free, + .map_mmap = ringbuf_map_mmap_user, + .map_lookup_elem = ringbuf_map_lookup_elem, + .map_update_elem = ringbuf_map_update_elem, + .map_delete_elem = ringbuf_map_delete_elem, + .map_get_next_key = ringbuf_map_get_next_key, + .map_btf_id = &user_ringbuf_map_btf_ids[0], +}; + /* Given pointer to ring buffer record metadata and struct bpf_ringbuf itself, * calculate offset from record metadata to ring buffer in pages, rounded * down. This page offset is stored as part of record metadata and allows to |