From 73375c92b0e7121595beaa84392bd6e5fa219daf Mon Sep 17 00:00:00 2001 From: Thadeu Lima de Souza Cascardo Date: Tue, 27 Apr 2021 10:12:12 -0300 Subject: [PATCH] UPSTREAM: 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") Change-Id: I1c0c43afd8047c5536a157c9c244cbbed6e95bd4 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 31cb04a4dd2d..51d0eb881ed3 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()) {