| Message ID | 20200630061500.1804799-1-andriin@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [v2,bpf] bpf: enforce BPF ringbuf size to be the power of 2 | expand |
On 6/30/20 8:15 AM, Andrii Nakryiko wrote: > BPF ringbuf assumes the size to be a multiple of page size and the power of > 2 value. The latter is important to avoid division while calculating position > inside the ring buffer and using (N-1) mask instead. This patch fixes omission > to enforce power-of-2 size rule. > > Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") > Signed-off-by: Andrii Nakryiko <andriin@fb.com> Lgtm, applied, thanks! [...] > @@ -166,9 +157,16 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) > return ERR_PTR(-EINVAL); > > if (attr->key_size || attr->value_size || > - attr->max_entries == 0 || !PAGE_ALIGNED(attr->max_entries)) > + !is_power_of_2(attr->max_entries) || > + !PAGE_ALIGNED(attr->max_entries)) Technically !IS_ALIGNED(attr->max_entries, PAGE_SIZE) might have been a bit cleaner since PAGE_ALIGNED() is only intended for pointers, though, not wrong here given max_entries is u32. Thanks, Daniel
On Tue, Jun 30, 2020 at 7:52 AM Daniel Borkmann <daniel@iogearbox.net> wrote: > > On 6/30/20 8:15 AM, Andrii Nakryiko wrote: > > BPF ringbuf assumes the size to be a multiple of page size and the power of > > 2 value. The latter is important to avoid division while calculating position > > inside the ring buffer and using (N-1) mask instead. This patch fixes omission > > to enforce power-of-2 size rule. > > > > Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") > > Signed-off-by: Andrii Nakryiko <andriin@fb.com> > > Lgtm, applied, thanks! > Thanks, Daniel! > [...] > > @@ -166,9 +157,16 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) > > return ERR_PTR(-EINVAL); > > > > if (attr->key_size || attr->value_size || > > - attr->max_entries == 0 || !PAGE_ALIGNED(attr->max_entries)) > > + !is_power_of_2(attr->max_entries) || > > + !PAGE_ALIGNED(attr->max_entries)) > > Technically !IS_ALIGNED(attr->max_entries, PAGE_SIZE) might have been a bit cleaner > since PAGE_ALIGNED() is only intended for pointers, though, not wrong here given > max_entries is u32. I've found a bunch of uses on non-pointers, e.g., `if (!PAGE_ALIGNED(fs_info->nodesize)) {` in BTRFS code, so assumed it's intended to be used more generically. But let me know if you want me to do IS_ALIGNED change. > > Thanks, > Daniel
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 180414bb0d3e..0af88bbc1c15 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -132,15 +132,6 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node) { struct bpf_ringbuf *rb; - if (!data_sz || !PAGE_ALIGNED(data_sz)) - return ERR_PTR(-EINVAL); - -#ifdef CONFIG_64BIT - /* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */ - if (data_sz > RINGBUF_MAX_DATA_SZ) - return ERR_PTR(-E2BIG); -#endif - rb = bpf_ringbuf_area_alloc(data_sz, numa_node); if (!rb) return ERR_PTR(-ENOMEM); @@ -166,9 +157,16 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr) return ERR_PTR(-EINVAL); if (attr->key_size || attr->value_size || - attr->max_entries == 0 || !PAGE_ALIGNED(attr->max_entries)) + !is_power_of_2(attr->max_entries) || + !PAGE_ALIGNED(attr->max_entries)) return ERR_PTR(-EINVAL); +#ifdef CONFIG_64BIT + /* on 32-bit arch, it's impossible to overflow record's hdr->pgoff */ + if (attr->max_entries > RINGBUF_MAX_DATA_SZ) + return ERR_PTR(-E2BIG); +#endif + rb_map = kzalloc(sizeof(*rb_map), GFP_USER); if (!rb_map) return ERR_PTR(-ENOMEM);
BPF ringbuf assumes the size to be a multiple of page size and the power of 2 value. The latter is important to avoid division while calculating position inside the ring buffer and using (N-1) mask instead. This patch fixes omission to enforce power-of-2 size rule. Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- kernel/bpf/ringbuf.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)