diff options
author | Matt Mullins <mmullins@fb.com> | 2019-04-26 11:49:47 -0700 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2019-04-26 19:04:19 -0700 |
commit | 9df1c28bb75217b244257152ab7d788bb2a386d0 (patch) | |
tree | 7fe10ffd9b59716b52b992f5663ec8b5102406b6 /kernel/bpf | |
parent | 34b8ab091f9ef57a2bb3c8c8359a0a03a8abf2f9 (diff) | |
download | linux-9df1c28bb75217b244257152ab7d788bb2a386d0.tar.bz2 |
bpf: add writable context for raw tracepoints
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>
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/syscall.c | 8 | ||||
-rw-r--r-- | kernel/bpf/verifier.c | 31 |
2 files changed, 37 insertions, 2 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index b0de49598341..ae141e745f92 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1789,12 +1789,16 @@ 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 423f242a5efb..2ef442c62c0e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -405,6 +405,7 @@ static const char * const reg_type_str[] = { [PTR_TO_SOCK_COMMON_OR_NULL] = "sock_common_or_null", [PTR_TO_TCP_SOCK] = "tcp_sock", [PTR_TO_TCP_SOCK_OR_NULL] = "tcp_sock_or_null", + [PTR_TO_TP_BUFFER] = "tp_buffer", }; static char slot_type_char[] = { @@ -1993,6 +1994,32 @@ 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 */ @@ -2137,6 +2164,10 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn err = check_sock_access(env, insn_idx, regno, off, size, t); if (!err && 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]); |