[PATCH bpf] bpf: enforce BPF ringbuf size to be the power of 2
From: Andrii Nakryiko <hidden>
Date: 2020-06-29 22:17:53
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [ringbuf], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
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 <redacted>
---
kernel/bpf/ringbuf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
index 180414bb0d3e..dcc8e8b9df10 100644
--- a/kernel/bpf/ringbuf.c
+++ b/kernel/bpf/ringbuf.c@@ -132,7 +132,7 @@ 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)) + if (!is_power_of_2(data_sz) || !PAGE_ALIGNED(data_sz)) return ERR_PTR(-EINVAL); #ifdef CONFIG_64BIT
@@ -166,7 +166,8 @@ 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); rb_map = kzalloc(sizeof(*rb_map), GFP_USER);
--
2.24.1