diff options
| -rw-r--r-- | include/linux/filter.h | 39 |
1 files changed, 29 insertions, 10 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h index f5b5891ed1ba..43aa1f8855c7 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -350,25 +350,43 @@ struct sk_filter { #define BPF_PROG_RUN(filter, ctx) (*filter->bpf_func)(ctx, filter->insnsi) +#define BPF_SKB_CB_LEN QDISC_CB_PRIV_LEN + +static inline u8 *bpf_skb_cb(struct sk_buff *skb) +{ + /* eBPF programs may read/write skb->cb[] area to transfer meta + * data between tail calls. Since this also needs to work with + * tc, that scratch memory is mapped to qdisc_skb_cb's data area. + * + * In some socket filter cases, the cb unfortunately needs to be + * saved/restored so that protocol specific skb->cb[] data won't + * be lost. In any case, due to unpriviledged eBPF programs + * attached to sockets, we need to clear the bpf_skb_cb() area + * to not leak previous contents to user space. + */ + BUILD_BUG_ON(FIELD_SIZEOF(struct __sk_buff, cb) != BPF_SKB_CB_LEN); + BUILD_BUG_ON(FIELD_SIZEOF(struct __sk_buff, cb) != + FIELD_SIZEOF(struct qdisc_skb_cb, data)); + + return qdisc_skb_cb(skb)->data; +} + static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog, struct sk_buff *skb) { - u8 *cb_data = qdisc_skb_cb(skb)->data; - u8 saved_cb[QDISC_CB_PRIV_LEN]; + u8 *cb_data = bpf_skb_cb(skb); + u8 cb_saved[BPF_SKB_CB_LEN]; u32 res; - BUILD_BUG_ON(FIELD_SIZEOF(struct __sk_buff, cb) != - QDISC_CB_PRIV_LEN); - if (unlikely(prog->cb_access)) { - memcpy(saved_cb, cb_data, sizeof(saved_cb)); - memset(cb_data, 0, sizeof(saved_cb)); + memcpy(cb_saved, cb_data, sizeof(cb_saved)); + memset(cb_data, 0, sizeof(cb_saved)); } res = BPF_PROG_RUN(prog, skb); if (unlikely(prog->cb_access)) - memcpy(cb_data, saved_cb, sizeof(saved_cb)); + memcpy(cb_data, cb_saved, sizeof(cb_saved)); return res; } @@ -376,10 +394,11 @@ static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog, static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog, struct sk_buff *skb) { - u8 *cb_data = qdisc_skb_cb(skb)->data; + u8 *cb_data = bpf_skb_cb(skb); if (unlikely(prog->cb_access)) - memset(cb_data, 0, QDISC_CB_PRIV_LEN); + memset(cb_data, 0, BPF_SKB_CB_LEN); + return BPF_PROG_RUN(prog, skb); } |