From db58ba45920255e967cc1d62a430cebd634b5046 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Thu, 5 May 2016 19:49:12 -0700 Subject: [PATCH] bpf: wire in data and data_end for cls_act_bpf allow cls_bpf and act_bpf programs access skb->data and skb->data_end pointers. The bpf helpers that change skb->data need to update data_end pointer as well. The verifier checks that programs always reload data, data_end pointers after calls to such bpf helpers. We cannot add 'data_end' pointer to struct qdisc_skb_cb directly, since it's embedded as-is by infiniband ipoib, so wrapper struct is needed. Signed-off-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- include/linux/filter.h | 16 +++++++++++++ net/core/filter.c | 51 +++++++++++++++++++++++++++++++++++++----- net/sched/act_bpf.c | 2 ++ net/sched/cls_bpf.c | 2 ++ 4 files changed, 65 insertions(+), 6 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 43aa1f8855c7..ec1411c89105 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -352,6 +352,22 @@ struct sk_filter { #define BPF_SKB_CB_LEN QDISC_CB_PRIV_LEN +struct bpf_skb_data_end { + struct qdisc_skb_cb qdisc_cb; + void *data_end; +}; + +/* compute the linear packet data range [data, data_end) which + * will be accessed by cls_bpf and act_bpf programs + */ +static inline void bpf_compute_data_end(struct sk_buff *skb) +{ + struct bpf_skb_data_end *cb = (struct bpf_skb_data_end *)skb->cb; + + BUILD_BUG_ON(sizeof(*cb) > FIELD_SIZEOF(struct sk_buff, cb)); + cb->data_end = skb->data + skb_headlen(skb); +} + static inline u8 *bpf_skb_cb(struct sk_buff *skb) { /* eBPF programs may read/write skb->cb[] area to transfer meta diff --git a/net/core/filter.c b/net/core/filter.c index 218e5de8c402..71c2a1f473ad 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1344,6 +1344,21 @@ struct bpf_scratchpad { static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp); +static inline int bpf_try_make_writable(struct sk_buff *skb, + unsigned int write_len) +{ + int err; + + if (!skb_cloned(skb)) + return 0; + if (skb_clone_writable(skb, write_len)) + return 0; + err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC); + if (!err) + bpf_compute_data_end(skb); + return err; +} + static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags) { struct bpf_scratchpad *sp = this_cpu_ptr(&bpf_sp); @@ -1366,7 +1381,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags) */ if (unlikely((u32) offset > 0xffff || len > sizeof(sp->buff))) return -EFAULT; - if (unlikely(skb_try_make_writable(skb, offset + len))) + if (unlikely(bpf_try_make_writable(skb, offset + len))) return -EFAULT; ptr = skb_header_pointer(skb, offset, len, sp->buff); @@ -1444,7 +1459,7 @@ static u64 bpf_l3_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags) return -EINVAL; if (unlikely((u32) offset > 0xffff)) return -EFAULT; - if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum)))) + if (unlikely(bpf_try_make_writable(skb, offset + sizeof(sum)))) return -EFAULT; ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum); @@ -1499,7 +1514,7 @@ static u64 bpf_l4_csum_replace(u64 r1, u64 r2, u64 from, u64 to, u64 flags) return -EINVAL; if (unlikely((u32) offset > 0xffff)) return -EFAULT; - if (unlikely(skb_try_make_writable(skb, offset + sizeof(sum)))) + if (unlikely(bpf_try_make_writable(skb, offset + sizeof(sum)))) return -EFAULT; ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum); @@ -1699,12 +1714,15 @@ static u64 bpf_skb_vlan_push(u64 r1, u64 r2, u64 vlan_tci, u64 r4, u64 r5) { struct sk_buff *skb = (struct sk_buff *) (long) r1; __be16 vlan_proto = (__force __be16) r2; + int ret; if (unlikely(vlan_proto != htons(ETH_P_8021Q) && vlan_proto != htons(ETH_P_8021AD))) vlan_proto = htons(ETH_P_8021Q); - return skb_vlan_push(skb, vlan_proto, vlan_tci); + ret = skb_vlan_push(skb, vlan_proto, vlan_tci); + bpf_compute_data_end(skb); + return ret; } const struct bpf_func_proto bpf_skb_vlan_push_proto = { @@ -1720,8 +1738,11 @@ EXPORT_SYMBOL_GPL(bpf_skb_vlan_push_proto); static u64 bpf_skb_vlan_pop(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) { struct sk_buff *skb = (struct sk_buff *) (long) r1; + int ret; - return skb_vlan_pop(skb); + ret = skb_vlan_pop(skb); + bpf_compute_data_end(skb); + return ret; } const struct bpf_func_proto bpf_skb_vlan_pop_proto = { @@ -2066,8 +2087,12 @@ static bool __is_valid_access(int off, int size, enum bpf_access_type type) static bool sk_filter_is_valid_access(int off, int size, enum bpf_access_type type) { - if (off == offsetof(struct __sk_buff, tc_classid)) + switch (off) { + case offsetof(struct __sk_buff, tc_classid): + case offsetof(struct __sk_buff, data): + case offsetof(struct __sk_buff, data_end): return false; + } if (type == BPF_WRITE) { switch (off) { @@ -2215,6 +2240,20 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg, *insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg, ctx_off); break; + case offsetof(struct __sk_buff, data): + *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, data)), + dst_reg, src_reg, + offsetof(struct sk_buff, data)); + break; + + case offsetof(struct __sk_buff, data_end): + ctx_off -= offsetof(struct __sk_buff, data_end); + ctx_off += offsetof(struct sk_buff, cb); + ctx_off += offsetof(struct bpf_skb_data_end, data_end); + *insn++ = BPF_LDX_MEM(bytes_to_bpf_size(sizeof(void *)), + dst_reg, src_reg, ctx_off); + break; + case offsetof(struct __sk_buff, tc_index): #ifdef CONFIG_NET_SCHED BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, tc_index) != 2); diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c index 4fd703362563..c7123e01c2ca 100644 --- a/net/sched/act_bpf.c +++ b/net/sched/act_bpf.c @@ -53,9 +53,11 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act, filter = rcu_dereference(prog->filter); if (at_ingress) { __skb_push(skb, skb->mac_len); + bpf_compute_data_end(skb); filter_res = BPF_PROG_RUN(filter, skb); __skb_pull(skb, skb->mac_len); } else { + bpf_compute_data_end(skb); filter_res = BPF_PROG_RUN(filter, skb); } rcu_read_unlock(); diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c index 425fe6a0eda3..7b342c779da7 100644 --- a/net/sched/cls_bpf.c +++ b/net/sched/cls_bpf.c @@ -96,9 +96,11 @@ static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp, if (at_ingress) { /* It is safe to push/pull even if skb_shared() */ __skb_push(skb, skb->mac_len); + bpf_compute_data_end(skb); filter_res = BPF_PROG_RUN(prog->filter, skb); __skb_pull(skb, skb->mac_len); } else { + bpf_compute_data_end(skb); filter_res = BPF_PROG_RUN(prog->filter, skb); }