From: Matt Mullins mmullins@fb.com
mainline inclusion from mainline-v5.2-rc1 commit 9df1c28bb75217b244257152ab7d788bb2a386d0 category: feature bugzilla: NA CVE: NA
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This is an opt-in interface that allows a tracepoint to provide a safe buffer that can be written from a BPF_PROG_TYPE_RAW_TRACEPOINT program. The size of the buffer must be a compile-time constant, and is checked before allowing a BPF program to attach to a tracepoint that uses this feature.
The pointer to this buffer will be the first argument of tracepoints that opt in; the pointer is valid and can be bpf_probe_read() by both BPF_PROG_TYPE_RAW_TRACEPOINT and BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE programs that attach to such a tracepoint, but the buffer to which it points may only be written by the latter.
Signed-off-by: Matt Mullins mmullins@fb.com Acked-by: Yonghong Song yhs@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Conflict: include/linux/bpf.h include/uapi/linux/bpf.h kernel/bpf/verifier.c Signed-off-by: Yufen Yu yuyufen@huawei.com Reviewed-by: Hou Tao houtao1@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- include/linux/bpf.h | 9 +++++++++ include/linux/bpf_types.h | 1 + include/linux/tracepoint-defs.h | 1 + include/trace/bpf_probe.h | 27 +++++++++++++++++++++++++-- include/uapi/linux/bpf.h | 3 +++ kernel/bpf/syscall.c | 8 ++++++-- kernel/bpf/verifier.c | 31 +++++++++++++++++++++++++++++++ kernel/trace/bpf_trace.c | 24 ++++++++++++++++++++++++ 8 files changed, 100 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 685bbc0139add..2eed5ecdcdc75 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -214,6 +214,14 @@ enum bpf_reg_type { PTR_TO_PACKET_META, /* skb->data - meta_len */ PTR_TO_PACKET, /* reg points to skb->data */ PTR_TO_PACKET_END, /* skb->data + headlen */ + PTR_TO_FLOW_KEYS, /* reg points to bpf_flow_keys */ + PTR_TO_SOCKET, /* reg points to struct bpf_sock */ + PTR_TO_SOCKET_OR_NULL, /* reg points to struct bpf_sock or NULL */ + PTR_TO_SOCK_COMMON, /* reg points to sock_common */ + PTR_TO_SOCK_COMMON_OR_NULL, /* reg points to sock_common or NULL */ + PTR_TO_TCP_SOCK, /* reg points to struct tcp_sock */ + PTR_TO_TCP_SOCK_OR_NULL, /* reg points to struct tcp_sock or NULL */ + PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */ };
/* The information passed from prog-specific *_is_valid_access @@ -285,6 +293,7 @@ struct bpf_prog_aux { atomic_t refcnt; u32 used_map_cnt; u32 max_ctx_offset; + u32 max_tp_access; u32 stack_depth; u32 id; u32 func_cnt; diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h index b3f9156a519ab..b5b9196a30134 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -22,6 +22,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_KPROBE, kprobe) BPF_PROG_TYPE(BPF_PROG_TYPE_TRACEPOINT, tracepoint) BPF_PROG_TYPE(BPF_PROG_TYPE_PERF_EVENT, perf_event) BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT, raw_tracepoint) +BPF_PROG_TYPE(BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, raw_tracepoint_writable) #endif #ifdef CONFIG_CGROUP_BPF BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_DEVICE, cg_dev) diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h index 49ba9cde7e4bb..b29950a19205e 100644 --- a/include/linux/tracepoint-defs.h +++ b/include/linux/tracepoint-defs.h @@ -45,6 +45,7 @@ struct bpf_raw_event_map { struct tracepoint *tp; void *bpf_func; u32 num_args; + u32 writable_size; } __aligned(32);
#endif diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h index 505dae0bed80b..d6e556c0a0852 100644 --- a/include/trace/bpf_probe.h +++ b/include/trace/bpf_probe.h @@ -69,8 +69,7 @@ __bpf_trace_##call(void *__data, proto) \ * to make sure that if the tracepoint handling changes, the * bpf probe will fail to compile unless it too is updated. */ -#undef DEFINE_EVENT -#define DEFINE_EVENT(template, call, proto, args) \ +#define __DEFINE_EVENT(template, call, proto, args, size) \ static inline void bpf_test_probe_##call(void) \ { \ check_trace_callback_type_##call(__bpf_trace_##template); \ @@ -81,12 +80,36 @@ __bpf_trace_tp_map_##call = { \ .tp = &__tracepoint_##call, \ .bpf_func = (void *)__bpf_trace_##template, \ .num_args = COUNT_ARGS(args), \ + .writable_size = size, \ };
+#define FIRST(x, ...) x + +#undef DEFINE_EVENT_WRITABLE +#define DEFINE_EVENT_WRITABLE(template, call, proto, args, size) \ +static inline void bpf_test_buffer_##call(void) \ +{ \ + /* BUILD_BUG_ON() is ignored if the code is completely eliminated, but \ + * BUILD_BUG_ON_ZERO() uses a different mechanism that is not \ + * dead-code-eliminated. \ + */ \ + FIRST(proto); \ + (void)BUILD_BUG_ON_ZERO(size != sizeof(*FIRST(args))); \ +} \ +__DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), size) + +#undef DEFINE_EVENT +#define DEFINE_EVENT(template, call, proto, args) \ + __DEFINE_EVENT(template, call, PARAMS(proto), PARAMS(args), 0)
#undef DEFINE_EVENT_PRINT #define DEFINE_EVENT_PRINT(template, name, proto, args, print) \ DEFINE_EVENT(template, name, PARAMS(proto), PARAMS(args))
#include TRACE_INCLUDE(TRACE_INCLUDE_FILE) + +#undef DEFINE_EVENT_WRITABLE +#undef __DEFINE_EVENT +#undef FIRST + #endif /* CONFIG_BPF_EVENTS */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 2bbae9e2786ea..b6ff566503d11 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -154,6 +154,9 @@ enum bpf_prog_type { BPF_PROG_TYPE_LWT_SEG6LOCAL, BPF_PROG_TYPE_LIRC_MODE2, BPF_PROG_TYPE_SK_REUSEPORT, + BPF_PROG_TYPE_FLOW_DISSECTOR, + BPF_PROG_TYPE_CGROUP_SYSCTL, + BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, };
enum bpf_attach_type { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index fc0628d133166..116c8b32c5716 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1578,12 +1578,16 @@ static int bpf_raw_tracepoint_open(const union bpf_attr *attr) } raw_tp->btp = btp;
- prog = bpf_prog_get_type(attr->raw_tracepoint.prog_fd, - BPF_PROG_TYPE_RAW_TRACEPOINT); + prog = bpf_prog_get(attr->raw_tracepoint.prog_fd); if (IS_ERR(prog)) { err = PTR_ERR(prog); goto out_free_tp; } + if (prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT && + prog->type != BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE) { + err = -EINVAL; + goto out_put_prog; + }
err = bpf_probe_register(raw_tp->btp, prog); if (err) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b748ec3dd6ba0..623c50e19ece9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -260,6 +260,7 @@ static const char * const reg_type_str[] = { [PTR_TO_PACKET] = "pkt", [PTR_TO_PACKET_META] = "pkt_meta", [PTR_TO_PACKET_END] = "pkt_end", + [PTR_TO_TP_BUFFER] = "tp_buffer", };
static char slot_type_char[] = { @@ -1590,6 +1591,32 @@ static int check_ctx_reg(struct bpf_verifier_env *env, return 0; }
+static int check_tp_buffer_access(struct bpf_verifier_env *env, + const struct bpf_reg_state *reg, + int regno, int off, int size) +{ + if (off < 0) { + verbose(env, + "R%d invalid tracepoint buffer access: off=%d, size=%d", + regno, off, size); + return -EACCES; + } + if (!tnum_is_const(reg->var_off) || reg->var_off.value) { + char tn_buf[48]; + + tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off); + verbose(env, + "R%d invalid variable buffer offset: off=%d, var_off=%s", + regno, off, tn_buf); + return -EACCES; + } + if (off + size > env->prog->aux->max_tp_access) + env->prog->aux->max_tp_access = off + size; + + return 0; +} + + /* truncate register to smaller size (in bytes) * must be called with size < BPF_REG_SIZE */ @@ -1709,6 +1736,10 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn err = check_packet_access(env, regno, off, size, false); if (!err && t == BPF_READ && value_regno >= 0) mark_reg_unknown(env, regs, value_regno); + } else if (reg->type == PTR_TO_TP_BUFFER) { + err = check_tp_buffer_access(env, reg, regno, off, size); + if (!err && t == BPF_READ && value_regno >= 0) + mark_reg_unknown(env, regs, value_regno); } else { verbose(env, "R%d invalid mem access '%s'\n", regno, reg_type_str[reg->type]); diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index bb5e8b1922a62..b8726b8a46022 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -978,6 +978,27 @@ const struct bpf_verifier_ops raw_tracepoint_verifier_ops = { const struct bpf_prog_ops raw_tracepoint_prog_ops = { };
+static bool raw_tp_writable_prog_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (off == 0) { + if (size != sizeof(u64) || type != BPF_READ) + return false; + info->reg_type = PTR_TO_TP_BUFFER; + } + return raw_tp_prog_is_valid_access(off, size, type, prog, info); +} + +const struct bpf_verifier_ops raw_tracepoint_writable_verifier_ops = { + .get_func_proto = raw_tp_prog_func_proto, + .is_valid_access = raw_tp_writable_prog_is_valid_access, +}; + +const struct bpf_prog_ops raw_tracepoint_writable_prog_ops = { +}; + static bool pe_prog_is_valid_access(int off, int size, enum bpf_access_type type, const struct bpf_prog *prog, struct bpf_insn_access_aux *info) @@ -1267,6 +1288,9 @@ static int __bpf_probe_register(struct bpf_raw_event_map *btp, struct bpf_prog * if (prog->aux->max_ctx_offset > btp->num_args * sizeof(u64)) return -EINVAL;
+ if (prog->aux->max_tp_access > btp->writable_size) + return -EINVAL; + return tracepoint_probe_register(tp, (void *)btp->bpf_func, prog); }