From mboxrd@z Thu Jan 1 00:00:00 1970 From: Willem de Bruijn Subject: [PATCH net 1/2] rose: limit sk_filter trim to payload Date: Tue, 12 Jul 2016 18:18:56 -0400 Message-ID: <1468361937-102786-2-git-send-email-willemdebruijn.kernel@gmail.com> References: <1468361937-102786-1-git-send-email-willemdebruijn.kernel@gmail.com> Cc: alexei.starovoitov@gmail.com, daniel@iogearbox.net, davem@davemloft.net, hannes@stressinduktion.org, eric.dumazet@gmail.com, Willem de Bruijn To: netdev@vger.kernel.org Return-path: Received: from mail-qt0-f193.google.com ([209.85.216.193]:35120 "EHLO mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750787AbcGLWf5 (ORCPT ); Tue, 12 Jul 2016 18:35:57 -0400 Received: by mail-qt0-f193.google.com with SMTP id q11so1078430qtb.2 for ; Tue, 12 Jul 2016 15:35:43 -0700 (PDT) In-Reply-To: <1468361937-102786-1-git-send-email-willemdebruijn.kernel@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Willem de Bruijn Sockets can have a filter program attached that drops or trims incoming packets based on the filter program return value. Rose requires data packets to have at least ROSE_MIN_LEN bytes. It verifies this on arrival in rose_route_frame and unconditionally pulls the bytes in rose_recvmsg. The filter can trim packets to below this value in-between, causing pull to fail, leaving the partial header at the time of skb_copy_datagram_msg. Place a lower bound on the size to which sk_filter may trim packets by introducing sk_filter_trim_cap and call this for rose packets. Signed-off-by: Willem de Bruijn --- No Fixes tag, because this codepath goes back to the start of the git repo history. --- include/linux/filter.h | 6 +++++- net/core/filter.c | 10 +++++----- net/rose/rose_in.c | 3 ++- 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 6fc31ef..8f74f3d 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -467,7 +467,11 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp) } #endif /* CONFIG_DEBUG_SET_MODULE_RONX */ -int sk_filter(struct sock *sk, struct sk_buff *skb); +int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap); +static inline int sk_filter(struct sock *sk, struct sk_buff *skb) +{ + return sk_filter_trim_cap(sk, skb, 1); +} struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err); void bpf_prog_free(struct bpf_prog *fp); diff --git a/net/core/filter.c b/net/core/filter.c index c4b330c..e759d90 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -53,9 +53,10 @@ #include /** - * sk_filter - run a packet through a socket filter + * sk_filter_trim_cap - run a packet through a socket filter * @sk: sock associated with &sk_buff * @skb: buffer to filter + * @cap: limit on how short the eBPF program may trim the packet * * Run the eBPF program and then cut skb->data to correct size returned by * the program. If pkt_len is 0 we toss packet. If skb->len is smaller @@ -64,7 +65,7 @@ * be accepted or -EPERM if the packet should be tossed. * */ -int sk_filter(struct sock *sk, struct sk_buff *skb) +int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap) { int err; struct sk_filter *filter; @@ -85,14 +86,13 @@ int sk_filter(struct sock *sk, struct sk_buff *skb) filter = rcu_dereference(sk->sk_filter); if (filter) { unsigned int pkt_len = bpf_prog_run_save_cb(filter->prog, skb); - - err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM; + err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM; } rcu_read_unlock(); return err; } -EXPORT_SYMBOL(sk_filter); +EXPORT_SYMBOL(sk_filter_trim_cap); static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5) { diff --git a/net/rose/rose_in.c b/net/rose/rose_in.c index 79c4abc..0a63947 100644 --- a/net/rose/rose_in.c +++ b/net/rose/rose_in.c @@ -164,7 +164,8 @@ static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int framety rose_frames_acked(sk, nr); if (ns == rose->vr) { rose_start_idletimer(sk); - if (sock_queue_rcv_skb(sk, skb) == 0) { + if (sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN) == 0 && + __sock_queue_rcv_skb(sk, skb) == 0) { rose->vr = (rose->vr + 1) % ROSE_MODULUS; queued = 1; } else { -- 2.8.0.rc3.226.g39d4020