1 files changed, 233 insertions, 108 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1dda9d81f12c..0399ac092b36 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -504,6 +504,13 @@ static bool is_ptr_cast_function(enum bpf_func_id func_id)
 		func_id == BPF_FUNC_skc_to_tcp_request_sock;
 }
 
+static bool is_cmpxchg_insn(const struct bpf_insn *insn)
+{
+	return BPF_CLASS(insn->code) == BPF_STX &&
+	       BPF_MODE(insn->code) == BPF_ATOMIC &&
+	       insn->imm == BPF_CMPXCHG;
+}
+
 /* string representation of 'enum bpf_reg_type' */
 static const char * const reg_type_str[] = {
 	[NOT_INIT]		= "?",
@@ -1120,7 +1127,7 @@ static void mark_ptr_not_null_reg(struct bpf_reg_state *reg)
 		reg->type = PTR_TO_RDWR_BUF;
 		break;
 	default:
-		WARN_ON("unknown nullable register type");
+		WARN_ONCE(1, "unknown nullable register type");
 	}
 }
 
@@ -1703,7 +1710,11 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	}
 
 	if (class == BPF_STX) {
-		if (reg->type != SCALAR_VALUE)
+		/* BPF_STX (including atomic variants) has multiple source
+		 * operands, one of which is a ptr. Check whether the caller is
+		 * asking about it.
+		 */
+		if (t == SRC_OP && reg->type != SCALAR_VALUE)
 			return true;
 		return BPF_SIZE(code) == BPF_DW;
 	}
@@ -1735,22 +1746,38 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	return true;
 }
 
-/* Return TRUE if INSN doesn't have explicit value define. */
-static bool insn_no_def(struct bpf_insn *insn)
+/* Return the regno defined by the insn, or -1. */
+static int insn_def_regno(const struct bpf_insn *insn)
 {
-	u8 class = BPF_CLASS(insn->code);
-
-	return (class == BPF_JMP || class == BPF_JMP32 ||
-		class == BPF_STX || class == BPF_ST);
+	switch (BPF_CLASS(insn->code)) {
+	case BPF_JMP:
+	case BPF_JMP32:
+	case BPF_ST:
+		return -1;
+	case BPF_STX:
+		if (BPF_MODE(insn->code) == BPF_ATOMIC &&
+		    (insn->imm & BPF_FETCH)) {
+			if (insn->imm == BPF_CMPXCHG)
+				return BPF_REG_0;
+			else
+				return insn->src_reg;
+		} else {
+			return -1;
+		}
+	default:
+		return insn->dst_reg;
+	}
 }
 
 /* Return TRUE if INSN has defined any 32-bit value explicitly. */
 static bool insn_has_def32(struct bpf_verifier_env *env, struct bpf_insn *insn)
 {
-	if (insn_no_def(insn))
+	int dst_reg = insn_def_regno(insn);
+
+	if (dst_reg == -1)
 		return false;
 
-	return !is_reg64(env, insn, insn->dst_reg, NULL, DST_OP);
+	return !is_reg64(env, insn, dst_reg, NULL, DST_OP);
 }
 
 static void mark_insn_zext(struct bpf_verifier_env *env,
@@ -5829,35 +5856,51 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
 	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,
-			      u32 *ptr_limit, u8 opcode, bool off_is_neg)
+			      const struct bpf_reg_state *off_reg,
+			      u32 *alu_limit, u8 opcode)
 {
+	bool off_is_neg = off_reg->smin_value < 0;
 	bool mask_to_left = (opcode == BPF_ADD &&  off_is_neg) ||
 			    (opcode == BPF_SUB && !off_is_neg);
-	u32 off;
+	u32 max = 0, ptr_limit = 0;
+
+	if (!tnum_is_const(off_reg->var_off) &&
+	    (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
+		return REASON_BOUNDS;
 
 	switch (ptr_reg->type) {
 	case PTR_TO_STACK:
-		/* Indirect variable offset stack access is prohibited in
-		 * unprivileged mode so it's not handled here.
+		/* Offset 0 is out-of-bounds, but acceptable start for the
+		 * left direction, see BPF_REG_FP. Also, unknown scalar
+		 * offset where we would need to deal with min/max bounds is
+		 * currently prohibited for unprivileged.
 		 */
-		off = ptr_reg->off + ptr_reg->var_off.value;
-		if (mask_to_left)
-			*ptr_limit = MAX_BPF_STACK + off;
-		else
-			*ptr_limit = -off;
-		return 0;
+		max = MAX_BPF_STACK + mask_to_left;
+		ptr_limit = -(ptr_reg->var_off.value + ptr_reg->off);
+		break;
 	case PTR_TO_MAP_VALUE:
-		if (mask_to_left) {
-			*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
-		} else {
-			off = ptr_reg->smin_value + ptr_reg->off;
-			*ptr_limit = ptr_reg->map_ptr->value_size - off;
-		}
-		return 0;
+		max = ptr_reg->map_ptr->value_size;
+		ptr_limit = (mask_to_left ?
+			     ptr_reg->smin_value :
+			     ptr_reg->umax_value) + ptr_reg->off;
+		break;
 	default:
-		return -EINVAL;
+		return REASON_TYPE;
 	}
+
+	if (ptr_limit >= max)
+		return REASON_LIMIT;
+	*alu_limit = ptr_limit;
+	return 0;
 }
 
 static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,
@@ -5875,7 +5918,7 @@ static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux,
 	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;
@@ -5894,19 +5937,28 @@ static int sanitize_val_alu(struct bpf_verifier_env *env,
 	return update_alu_sanitation_state(aux, BPF_ALU_NON_POINTER, 0);
 }
 
+static bool sanitize_needed(u8 opcode)
+{
+	return opcode == BPF_ADD || opcode == BPF_SUB;
+}
+
 static int sanitize_ptr_alu(struct bpf_verifier_env *env,
 			    struct bpf_insn *insn,
 			    const struct bpf_reg_state *ptr_reg,
+			    const struct bpf_reg_state *off_reg,
 			    struct bpf_reg_state *dst_reg,
-			    bool off_is_neg)
+			    struct bpf_insn_aux_data *tmp_aux,
+			    const bool commit_window)
 {
+	struct bpf_insn_aux_data *aux = commit_window ? cur_aux(env) : tmp_aux;
 	struct bpf_verifier_state *vstate = env->cur_state;
-	struct bpf_insn_aux_data *aux = cur_aux(env);
+	bool off_is_neg = off_reg->smin_value < 0;
 	bool ptr_is_dst_reg = ptr_reg == dst_reg;
 	u8 opcode = BPF_OP(insn->code);
 	u32 alu_state, alu_limit;
 	struct bpf_reg_state tmp;
 	bool ret;
+	int err;
 
 	if (can_skip_alu_sanitation(env, insn))
 		return 0;
@@ -5918,15 +5970,33 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env,
 	if (vstate->speculative)
 		goto do_sim;
 
-	alu_state  = off_is_neg ? BPF_ALU_NEG_VALUE : 0;
-	alu_state |= ptr_is_dst_reg ?
-		     BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;
+	err = retrieve_ptr_limit(ptr_reg, off_reg, &alu_limit, opcode);
+	if (err < 0)
+		return err;
 
-	if (retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg))
-		return 0;
-	if (update_alu_sanitation_state(aux, alu_state, alu_limit))
-		return -EACCES;
+	if (commit_window) {
+		/* In commit phase we narrow the masking window based on
+		 * the observed pointer move after the simulated operation.
+		 */
+		alu_state = tmp_aux->alu_state;
+		alu_limit = abs(tmp_aux->alu_limit - alu_limit);
+	} else {
+		alu_state  = off_is_neg ? BPF_ALU_NEG_VALUE : 0;
+		alu_state |= ptr_is_dst_reg ?
+			     BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;
+	}
+
+	err = update_alu_sanitation_state(aux, alu_state, alu_limit);
+	if (err < 0)
+		return err;
 do_sim:
+	/* If we're in commit phase, we're done here given we already
+	 * pushed the truncated dst_reg into the speculative verification
+	 * stack.
+	 */
+	if (commit_window)
+		return 0;
+
 	/* Simulate and find potential out-of-bounds access under
 	 * speculative execution from truncation as a result of
 	 * masking when off was not within expected range. If off
@@ -5943,7 +6013,46 @@ 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;
 }
 
 /* check that stack access falls within stack limits and that 'reg' doesn't
@@ -5980,6 +6089,37 @@ static int check_stack_access_for_ptr_arithmetic(
 	return 0;
 }
 
+static int sanitize_check_bounds(struct bpf_verifier_env *env,
+				 const struct bpf_insn *insn,
+				 const struct bpf_reg_state *dst_reg)
+{
+	u32 dst = insn->dst_reg;
+
+	/* For unprivileged we require that resulting offset must be in bounds
+	 * in order to be able to sanitize access later on.
+	 */
+	if (env->bypass_spec_v1)
+		return 0;
+
+	switch (dst_reg->type) {
+	case PTR_TO_STACK:
+		if (check_stack_access_for_ptr_arithmetic(env, dst, dst_reg,
+					dst_reg->off + dst_reg->var_off.value))
+			return -EACCES;
+		break;
+	case PTR_TO_MAP_VALUE:
+		if (check_map_access(env, dst, dst_reg->off, 1, false)) {
+			verbose(env, "R%d pointer arithmetic of map value goes out of range, "
+				"prohibited for !root\n", dst);
+			return -EACCES;
+		}
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
 
 /* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
  * Caller should also handle BPF_MOV case separately.
@@ -5999,8 +6139,9 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	    smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
 	u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
 	    umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
-	u32 dst = insn->dst_reg, src = insn->src_reg;
+	struct bpf_insn_aux_data tmp_aux = {};
 	u8 opcode = BPF_OP(insn->code);
+	u32 dst = insn->dst_reg;
 	int ret;
 
 	dst_reg = &regs[dst];
@@ -6048,13 +6189,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		verbose(env, "R%d pointer arithmetic on %s prohibited\n",
 			dst, reg_type_str[ptr_reg->type]);
 		return -EACCES;
-	case PTR_TO_MAP_VALUE:
-		if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
-			verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
-				off_reg == dst_reg ? dst : src);
-			return -EACCES;
-		}
-		fallthrough;
 	default:
 		break;
 	}
@@ -6072,13 +6206,15 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	/* pointer types do not carry 32-bit bounds at the moment. */
 	__mark_reg32_unbounded(dst_reg);
 
+	if (sanitize_needed(opcode)) {
+		ret = sanitize_ptr_alu(env, insn, ptr_reg, off_reg, dst_reg,
+				       &tmp_aux, false);
+		if (ret < 0)
+			return sanitize_err(env, insn, ret, off_reg, dst_reg);
+	}
+
 	switch (opcode) {
 	case BPF_ADD:
-		ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
-		if (ret < 0) {
-			verbose(env, "R%d tried to add from different maps or paths\n", dst);
-			return ret;
-		}
 		/* We can take a fixed offset as long as it doesn't overflow
 		 * the s32 'off' field
 		 */
@@ -6129,11 +6265,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		}
 		break;
 	case BPF_SUB:
-		ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
-		if (ret < 0) {
-			verbose(env, "R%d tried to sub from different maps or paths\n", dst);
-			return ret;
-		}
 		if (dst_reg == off_reg) {
 			/* scalar -= pointer.  Creates an unknown scalar */
 			verbose(env, "R%d tried to subtract pointer from scalar\n",
@@ -6214,21 +6345,13 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	__reg_deduce_bounds(dst_reg);
 	__reg_bound_offset(dst_reg);
 
-	/* For unprivileged we require that resulting offset must be in bounds
-	 * in order to be able to sanitize access later on.
-	 */
-	if (!env->bypass_spec_v1) {
-		if (dst_reg->type == PTR_TO_MAP_VALUE &&
-		    check_map_access(env, dst, dst_reg->off, 1, false)) {
-			verbose(env, "R%d pointer arithmetic of map value goes out of range, "
-				"prohibited for !root\n", dst);
-			return -EACCES;
-		} else if (dst_reg->type == PTR_TO_STACK &&
-			   check_stack_access_for_ptr_arithmetic(
-				   env, dst, dst_reg, dst_reg->off +
-				   dst_reg->var_off.value)) {
-			return -EACCES;
-		}
+	if (sanitize_check_bounds(env, insn, dst_reg) < 0)
+		return -EACCES;
+	if (sanitize_needed(opcode)) {
+		ret = sanitize_ptr_alu(env, insn, dst_reg, off_reg, dst_reg,
+				       &tmp_aux, true);
+		if (ret < 0)
+			return sanitize_err(env, insn, ret, off_reg, dst_reg);
 	}
 
 	return 0;
@@ -6822,9 +6945,8 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 	s32 s32_min_val, s32_max_val;
 	u32 u32_min_val, u32_max_val;
 	u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
-	u32 dst = insn->dst_reg;
-	int ret;
 	bool alu32 = (BPF_CLASS(insn->code) != BPF_ALU64);
+	int ret;
 
 	smin_val = src_reg.smin_value;
 	smax_val = src_reg.smax_value;
@@ -6866,6 +6988,12 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 		return 0;
 	}
 
+	if (sanitize_needed(opcode)) {
+		ret = sanitize_val_alu(env, insn);
+		if (ret < 0)
+			return sanitize_err(env, insn, ret, NULL, NULL);
+	}
+
 	/* Calculate sign/unsigned bounds and tnum for alu32 and alu64 bit ops.
 	 * There are two classes of instructions: The first class we track both
 	 * alu32 and alu64 sign/unsigned bounds independently this provides the
@@ -6882,21 +7010,11 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
 	 */
 	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;
-		}
 		scalar32_min_max_add(dst_reg, &src_reg);
 		scalar_min_max_add(dst_reg, &src_reg);
 		dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
 		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;
-		}
 		scalar32_min_max_sub(dst_reg, &src_reg);
 		scalar_min_max_sub(dst_reg, &src_reg);
 		dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);
@@ -9029,6 +9147,10 @@ static int check_btf_info(struct bpf_verifier_env *env,
 	btf = btf_get_by_fd(attr->prog_btf_fd);
 	if (IS_ERR(btf))
 		return PTR_ERR(btf);
+	if (btf_is_kernel(btf)) {
+		btf_put(btf);
+		return -EACCES;
+	}
 	env->prog->aux->btf = btf;
 
 	err = check_btf_func(env, attr, uattr);
@@ -11006,9 +11128,10 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
 	for (i = 0; i < len; i++) {
 		int adj_idx = i + delta;
 		struct bpf_insn insn;
-		u8 load_reg;
+		int load_reg;
 
 		insn = insns[adj_idx];
+		load_reg = insn_def_regno(&insn);
 		if (!aux[adj_idx].zext_dst) {
 			u8 code, class;
 			u32 imm_rnd;
@@ -11018,14 +11141,14 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
 
 			code = insn.code;
 			class = BPF_CLASS(code);
-			if (insn_no_def(&insn))
+			if (load_reg == -1)
 				continue;
 
 			/* NOTE: arg "reg" (the fourth one) is only used for
-			 *       BPF_STX which has been ruled out in above
-			 *       check, it is safe to pass NULL here.
+			 *       BPF_STX + SRC_OP, so it is safe to pass NULL
+			 *       here.
 			 */
-			if (is_reg64(env, &insn, insn.dst_reg, NULL, DST_OP)) {
+			if (is_reg64(env, &insn, load_reg, NULL, DST_OP)) {
 				if (class == BPF_LD &&
 				    BPF_MODE(code) == BPF_IMM)
 					i++;
@@ -11040,31 +11163,28 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
 			imm_rnd = get_random_int();
 			rnd_hi32_patch[0] = insn;
 			rnd_hi32_patch[1].imm = imm_rnd;
-			rnd_hi32_patch[3].dst_reg = insn.dst_reg;
+			rnd_hi32_patch[3].dst_reg = load_reg;
 			patch = rnd_hi32_patch;
 			patch_len = 4;
 			goto apply_patch_buffer;
 		}
 
-		if (!bpf_jit_needs_zext())
+		/* Add in an zero-extend instruction if a) the JIT has requested
+		 * it or b) it's a CMPXCHG.
+		 *
+		 * The latter is because: BPF_CMPXCHG always loads a value into
+		 * R0, therefore always zero-extends. However some archs'
+		 * equivalent instruction only does this load when the
+		 * comparison is successful. This detail of CMPXCHG is
+		 * orthogonal to the general zero-extension behaviour of the
+		 * CPU, so it's treated independently of bpf_jit_needs_zext.
+		 */
+		if (!bpf_jit_needs_zext() && !is_cmpxchg_insn(&insn))
 			continue;
 
-		/* zext_dst means that we want to zero-extend whatever register
-		 * the insn defines, which is dst_reg most of the time, with
-		 * the notable exception of BPF_STX + BPF_ATOMIC + BPF_FETCH.
-		 */
-		if (BPF_CLASS(insn.code) == BPF_STX &&
-		    BPF_MODE(insn.code) == BPF_ATOMIC) {
-			/* BPF_STX + BPF_ATOMIC insns without BPF_FETCH do not
-			 * define any registers, therefore zext_dst cannot be
-			 * set.
-			 */
-			if (WARN_ON(!(insn.imm & BPF_FETCH)))
-				return -EINVAL;
-			load_reg = insn.imm == BPF_CMPXCHG ? BPF_REG_0
-							   : insn.src_reg;
-		} else {
-			load_reg = insn.dst_reg;
+		if (WARN_ON(load_reg == -1)) {
+			verbose(env, "verifier bug. zext_dst is set, but no reg is defined\n");
+			return -EFAULT;
 		}
 
 		zext_patch[0] = insn;
@@ -11635,7 +11755,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env)
 			off_reg = issrc ? insn->src_reg : insn->dst_reg;
 			if (isneg)
 				*patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
-			*patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit - 1);
+			*patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit);
 			*patch++ = BPF_ALU64_REG(BPF_SUB, BPF_REG_AX, off_reg);
 			*patch++ = BPF_ALU64_REG(BPF_OR, BPF_REG_AX, off_reg);
 			*patch++ = BPF_ALU64_IMM(BPF_NEG, BPF_REG_AX, 0);
@@ -12120,6 +12240,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
 	u32 btf_id, member_idx;
 	const char *mname;
 
+	if (!prog->gpl_compatible) {
+		verbose(env, "struct ops programs must have a GPL compatible license\n");
+		return -EINVAL;
+	}
+
 	btf_id = prog->aux->attach_btf_id;
 	st_ops = bpf_struct_ops_find(btf_id);
 	if (!st_ops) {