From 1ca284f0867079a34f52a6f811747695828166c6 Mon Sep 17 00:00:00 2001 From: Thadeu Lima de Souza Cascardo Date: Tue, 27 Apr 2021 10:12:12 -0300 Subject: [PATCH] bpf, ringbuf: Deny reserve of buffers larger than ringbuf commit 4b81ccebaeee885ab1aa1438133f2991e3a2b6ea upstream. A BPF program might try to reserve a buffer larger than the ringbuf size. If the consumer pointer is way ahead of the producer, that would be successfully reserved, allowing the BPF program to read or write out of the ringbuf allocated area. Reported-by: Ryota Shiga (Flatt Security) Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it") Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Daniel Borkmann Acked-by: Andrii Nakryiko Acked-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/ringbuf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c index 31cb04a..51d0eb88 100644 --- a/kernel/bpf/ringbuf.c +++ b/kernel/bpf/ringbuf.c @@ -334,6 +334,9 @@ static void *__bpf_ringbuf_reserve(struct bpf_ringbuf *rb, u64 size) return NULL; len = round_up(size + BPF_RINGBUF_HDR_SZ, 8); + if (len > rb->mask + 1) + return NULL; + cons_pos = smp_load_acquire(&rb->consumer_pos); if (in_nmi()) { -- 2.7.4