diff options
| author | Alexei Starovoitov <ast@fb.com> | 2016-06-15 18:25:38 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-06-15 23:37:54 -0700 |
| commit | 19de99f70b87fcc3338da52a89c439b088cbff71 (patch) | |
| tree | 43b5ff80043ee9ea62e09fe568502c9d68a188ee /kernel/bpf | |
| parent | e582615ad33dbd39623084a02e95567b116e1eea (diff) | |
bpf: fix matching of data/data_end in verifier
The ctx structure passed into bpf programs is different depending on bpf
program type. The verifier incorrectly marked ctx->data and ctx->data_end
access based on ctx offset only. That caused loads in tracing programs
int bpf_prog(struct pt_regs *ctx) { .. ctx->ax .. }
to be incorrectly marked as PTR_TO_PACKET which later caused verifier
to reject the program that was actually valid in tracing context.
Fix this by doing program type specific matching of ctx offsets.
Fixes: 969bf05eb3ce ("bpf: direct packet access")
Reported-by: Sasha Goldshtein <goldshtn@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 41 |
1 files changed, 7 insertions, 34 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 668e07903c8f..eec9f90ba030 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -126,31 +126,6 @@ * are set to NOT_INIT to indicate that they are no longer readable. */ -/* types of values stored in eBPF registers */ -enum bpf_reg_type { - NOT_INIT = 0, /* nothing was written into register */ - UNKNOWN_VALUE, /* reg doesn't contain a valid pointer */ - PTR_TO_CTX, /* reg points to bpf_context */ - CONST_PTR_TO_MAP, /* reg points to struct bpf_map */ - PTR_TO_MAP_VALUE, /* reg points to map element value */ - PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */ - FRAME_PTR, /* reg == frame_pointer */ - PTR_TO_STACK, /* reg == frame_pointer + imm */ - CONST_IMM, /* constant integer value */ - - /* PTR_TO_PACKET represents: - * skb->data - * skb->data + imm - * skb->data + (u16) var - * skb->data + (u16) var + imm - * if (range > 0) then [ptr, ptr + range - off) is safe to access - * if (id > 0) means that some 'var' was added - * if (off > 0) menas that 'imm' was added - */ - PTR_TO_PACKET, - PTR_TO_PACKET_END, /* skb->data + headlen */ -}; - struct reg_state { enum bpf_reg_type type; union { @@ -695,10 +670,10 @@ static int check_packet_access(struct verifier_env *env, u32 regno, int off, /* check access to 'struct bpf_context' fields */ static int check_ctx_access(struct verifier_env *env, int off, int size, - enum bpf_access_type t) + enum bpf_access_type t, enum bpf_reg_type *reg_type) { if (env->prog->aux->ops->is_valid_access && - env->prog->aux->ops->is_valid_access(off, size, t)) { + env->prog->aux->ops->is_valid_access(off, size, t, reg_type)) { /* remember the offset of last byte accessed in ctx */ if (env->prog->aux->max_ctx_offset < off + size) env->prog->aux->max_ctx_offset = off + size; @@ -798,21 +773,19 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, mark_reg_unknown_value(state->regs, value_regno); } else if (reg->type == PTR_TO_CTX) { + enum bpf_reg_type reg_type = UNKNOWN_VALUE; + if (t == BPF_WRITE && value_regno >= 0 && is_pointer_value(env, value_regno)) { verbose("R%d leaks addr into ctx\n", value_regno); return -EACCES; } - err = check_ctx_access(env, off, size, t); + err = check_ctx_access(env, off, size, t, ®_type); if (!err && t == BPF_READ && value_regno >= 0) { mark_reg_unknown_value(state->regs, value_regno); - if (off == offsetof(struct __sk_buff, data) && - env->allow_ptr_leaks) + if (env->allow_ptr_leaks) /* note that reg.[id|off|range] == 0 */ - state->regs[value_regno].type = PTR_TO_PACKET; - else if (off == offsetof(struct __sk_buff, data_end) && - env->allow_ptr_leaks) - state->regs[value_regno].type = PTR_TO_PACKET_END; + state->regs[value_regno].type = reg_type; } } else if (reg->type == FRAME_PTR || reg->type == PTR_TO_STACK) { |