From: Daniel Borkmann daniel@iogearbox.net
commit a6aaece00a57fa6f22575364b3903dfbccf5345d upstream.
Consolidate all error handling and provide more user-friendly error messages from sanitize_ptr_alu() and sanitize_val_alu().
Signed-off-by: Daniel Borkmann daniel@iogearbox.net Reviewed-by: John Fastabend john.fastabend@gmail.com Acked-by: Alexei Starovoitov ast@kernel.org [fllinden@amazon.com: backport to 5.4] Signed-off-by: Frank van der Linden fllinden@amazon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 84 ++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 62 insertions(+), 22 deletions(-)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4263,6 +4263,14 @@ static struct bpf_insn_aux_data *cur_aux return &env->insn_aux_data[env->insn_idx]; }
+enum { + REASON_BOUNDS = -1, + REASON_TYPE = -2, + REASON_PATHS = -3, + REASON_LIMIT = -4, + REASON_STACK = -5, +}; + static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, const struct bpf_reg_state *off_reg, u32 *alu_limit, u8 opcode) @@ -4274,7 +4282,7 @@ static int retrieve_ptr_limit(const stru
if (!tnum_is_const(off_reg->var_off) && (off_reg->smin_value < 0) != (off_reg->smax_value < 0)) - return -EACCES; + return REASON_BOUNDS;
switch (ptr_reg->type) { case PTR_TO_STACK: @@ -4301,11 +4309,11 @@ static int retrieve_ptr_limit(const stru } break; default: - return -EINVAL; + return REASON_TYPE; }
if (ptr_limit >= max) - return -ERANGE; + return REASON_LIMIT; *alu_limit = ptr_limit; return 0; } @@ -4325,7 +4333,7 @@ static int update_alu_sanitation_state(s if (aux->alu_state && (aux->alu_state != alu_state || aux->alu_limit != alu_limit)) - return -EACCES; + return REASON_PATHS;
/* Corresponding fixup done in fixup_bpf_calls(). */ aux->alu_state = alu_state; @@ -4398,7 +4406,46 @@ do_sim: ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true); if (!ptr_is_dst_reg && ret) *dst_reg = tmp; - return !ret ? -EFAULT : 0; + return !ret ? REASON_STACK : 0; +} + +static int sanitize_err(struct bpf_verifier_env *env, + const struct bpf_insn *insn, int reason, + const struct bpf_reg_state *off_reg, + const struct bpf_reg_state *dst_reg) +{ + static const char *err = "pointer arithmetic with it prohibited for !root"; + const char *op = BPF_OP(insn->code) == BPF_ADD ? "add" : "sub"; + u32 dst = insn->dst_reg, src = insn->src_reg; + + switch (reason) { + case REASON_BOUNDS: + verbose(env, "R%d has unknown scalar with mixed signed bounds, %s\n", + off_reg == dst_reg ? dst : src, err); + break; + case REASON_TYPE: + verbose(env, "R%d has pointer with unsupported alu operation, %s\n", + off_reg == dst_reg ? src : dst, err); + break; + case REASON_PATHS: + verbose(env, "R%d tried to %s from different maps, paths or scalars, %s\n", + dst, op, err); + break; + case REASON_LIMIT: + verbose(env, "R%d tried to %s beyond pointer bounds, %s\n", + dst, op, err); + break; + case REASON_STACK: + verbose(env, "R%d could not be pushed for speculative verification, %s\n", + dst, err); + break; + default: + verbose(env, "verifier internal error: unknown reason (%d)\n", + reason); + break; + } + + return -EACCES; }
/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off. @@ -4480,10 +4527,9 @@ static int adjust_ptr_min_max_vals(struc switch (opcode) { case BPF_ADD: ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg); - if (ret < 0) { - verbose(env, "R%d tried to add from different maps, paths, or prohibited types\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, off_reg, dst_reg); + /* We can take a fixed offset as long as it doesn't overflow * the s32 'off' field */ @@ -4535,10 +4581,9 @@ static int adjust_ptr_min_max_vals(struc break; case BPF_SUB: ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg); - if (ret < 0) { - verbose(env, "R%d tried to sub from different maps, paths, or prohibited types\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, off_reg, dst_reg); + if (dst_reg == off_reg) { /* scalar -= pointer. Creates an unknown scalar */ verbose(env, "R%d tried to subtract pointer from scalar\n", @@ -4655,7 +4700,6 @@ static int adjust_scalar_min_max_vals(st s64 smin_val, smax_val; u64 umin_val, umax_val; u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32; - u32 dst = insn->dst_reg; int ret;
if (insn_bitness == 32) { @@ -4692,10 +4736,8 @@ static int adjust_scalar_min_max_vals(st switch (opcode) { case BPF_ADD: ret = sanitize_val_alu(env, insn); - if (ret < 0) { - verbose(env, "R%d tried to add from different pointers or scalars\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, NULL, NULL); if (signed_add_overflows(dst_reg->smin_value, smin_val) || signed_add_overflows(dst_reg->smax_value, smax_val)) { dst_reg->smin_value = S64_MIN; @@ -4716,10 +4758,8 @@ static int adjust_scalar_min_max_vals(st break; case BPF_SUB: ret = sanitize_val_alu(env, insn); - if (ret < 0) { - verbose(env, "R%d tried to sub from different pointers or scalars\n", dst); - return ret; - } + if (ret < 0) + return sanitize_err(env, insn, ret, NULL, NULL); if (signed_sub_overflows(dst_reg->smin_value, smax_val) || signed_sub_overflows(dst_reg->smax_value, smin_val)) { /* Overflow possible, we know nothing */