1 files changed, 49 insertions, 99 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 475c28e21128..5ea2238a6656 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2667,6 +2667,19 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 	cur = env->cur_state->frame[env->cur_state->curframe];
 	if (value_regno >= 0)
 		reg = &cur->regs[value_regno];
+	if (!env->bypass_spec_v4) {
+		bool sanitize = reg && is_spillable_regtype(reg->type);
+
+		for (i = 0; i < size; i++) {
+			if (state->stack[spi].slot_type[i] == STACK_INVALID) {
+				sanitize = true;
+				break;
+			}
+		}
+
+		if (sanitize)
+			env->insn_aux_data[insn_idx].sanitize_stack_spill = true;
+	}
 
 	if (reg && size == BPF_REG_SIZE && register_is_bounded(reg) &&
 	    !register_is_null(reg) && env->bpf_capable) {
@@ -2689,47 +2702,10 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 			verbose(env, "invalid size of register spill\n");
 			return -EACCES;
 		}
-
 		if (state != cur && reg->type == PTR_TO_STACK) {
 			verbose(env, "cannot spill pointers to stack into stack frame of the caller\n");
 			return -EINVAL;
 		}
-
-		if (!env->bypass_spec_v4) {
-			bool sanitize = false;
-
-			if (state->stack[spi].slot_type[0] == STACK_SPILL &&
-			    register_is_const(&state->stack[spi].spilled_ptr))
-				sanitize = true;
-			for (i = 0; i < BPF_REG_SIZE; i++)
-				if (state->stack[spi].slot_type[i] == STACK_MISC) {
-					sanitize = true;
-					break;
-				}
-			if (sanitize) {
-				int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off;
-				int soff = (-spi - 1) * BPF_REG_SIZE;
-
-				/* detected reuse of integer stack slot with a pointer
-				 * which means either llvm is reusing stack slot or
-				 * an attacker is trying to exploit CVE-2018-3639
-				 * (speculative store bypass)
-				 * Have to sanitize that slot with preemptive
-				 * store of zero.
-				 */
-				if (*poff && *poff != soff) {
-					/* disallow programs where single insn stores
-					 * into two different stack slots, since verifier
-					 * cannot sanitize them
-					 */
-					verbose(env,
-						"insn %d cannot access two stack slots fp%d and fp%d",
-						insn_idx, *poff, soff);
-					return -EINVAL;
-				}
-				*poff = soff;
-			}
-		}
 		save_register_state(state, spi, reg);
 	} else {
 		u8 type = STACK_MISC;
@@ -6804,6 +6780,12 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env,
 		alu_state |= off_is_imm ? BPF_ALU_IMMEDIATE : 0;
 		alu_state |= ptr_is_dst_reg ?
 			     BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;
+
+		/* Limit pruning on unknown scalars to enable deep search for
+		 * potential masking differences from other program paths.
+		 */
+		if (!off_is_imm)
+			env->explore_alu_limits = true;
 	}
 
 	err = update_alu_sanitation_state(aux, alu_state, alu_limit);
@@ -10207,8 +10189,8 @@ next:
 }
 
 /* Returns true if (rold safe implies rcur safe) */
-static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
-		    struct bpf_id_pair *idmap)
+static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
+		    struct bpf_reg_state *rcur, struct bpf_id_pair *idmap)
 {
 	bool equal;
 
@@ -10234,6 +10216,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
 		return false;
 	switch (rold->type) {
 	case SCALAR_VALUE:
+		if (env->explore_alu_limits)
+			return false;
 		if (rcur->type == SCALAR_VALUE) {
 			if (!rold->precise && !rcur->precise)
 				return true;
@@ -10324,9 +10308,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
 	return false;
 }
 
-static bool stacksafe(struct bpf_func_state *old,
-		      struct bpf_func_state *cur,
-		      struct bpf_id_pair *idmap)
+static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old,
+		      struct bpf_func_state *cur, struct bpf_id_pair *idmap)
 {
 	int i, spi;
 
@@ -10371,9 +10354,8 @@ static bool stacksafe(struct bpf_func_state *old,
 			continue;
 		if (old->stack[spi].slot_type[0] != STACK_SPILL)
 			continue;
-		if (!regsafe(&old->stack[spi].spilled_ptr,
-			     &cur->stack[spi].spilled_ptr,
-			     idmap))
+		if (!regsafe(env, &old->stack[spi].spilled_ptr,
+			     &cur->stack[spi].spilled_ptr, idmap))
 			/* when explored and current stack slot are both storing
 			 * spilled registers, check that stored pointers types
 			 * are the same as well.
@@ -10430,10 +10412,11 @@ static bool func_states_equal(struct bpf_verifier_env *env, struct bpf_func_stat
 
 	memset(env->idmap_scratch, 0, sizeof(env->idmap_scratch));
 	for (i = 0; i < MAX_BPF_REG; i++)
-		if (!regsafe(&old->regs[i], &cur->regs[i], env->idmap_scratch))
+		if (!regsafe(env, &old->regs[i], &cur->regs[i],
+			     env->idmap_scratch))
 			return false;
 
-	if (!stacksafe(old, cur, env->idmap_scratch))
+	if (!stacksafe(env, old, cur, env->idmap_scratch))
 		return false;
 
 	if (!refsafe(old, cur))
@@ -12198,35 +12181,33 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		bpf_convert_ctx_access_t convert_ctx_access;
+		bool ctx_access;
 
 		if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
 		    insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
 		    insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
-		    insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
+		    insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) {
 			type = BPF_READ;
-		else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
-			 insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
-			 insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
-			 insn->code == (BPF_STX | BPF_MEM | BPF_DW))
+			ctx_access = true;
+		} else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
+			   insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
+			   insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
+			   insn->code == (BPF_STX | BPF_MEM | BPF_DW) ||
+			   insn->code == (BPF_ST | BPF_MEM | BPF_B) ||
+			   insn->code == (BPF_ST | BPF_MEM | BPF_H) ||
+			   insn->code == (BPF_ST | BPF_MEM | BPF_W) ||
+			   insn->code == (BPF_ST | BPF_MEM | BPF_DW)) {
 			type = BPF_WRITE;
-		else
+			ctx_access = BPF_CLASS(insn->code) == BPF_STX;
+		} else {
 			continue;
+		}
 
 		if (type == BPF_WRITE &&
-		    env->insn_aux_data[i + delta].sanitize_stack_off) {
+		    env->insn_aux_data[i + delta].sanitize_stack_spill) {
 			struct bpf_insn patch[] = {
-				/* Sanitize suspicious stack slot with zero.
-				 * There are no memory dependencies for this store,
-				 * since it's only using frame pointer and immediate
-				 * constant of zero
-				 */
-				BPF_ST_MEM(BPF_DW, BPF_REG_FP,
-					   env->insn_aux_data[i + delta].sanitize_stack_off,
-					   0),
-				/* the original STX instruction will immediately
-				 * overwrite the same stack slot with appropriate value
-				 */
 				*insn,
+				BPF_ST_NOSPEC(),
 			};
 
 			cnt = ARRAY_SIZE(patch);
@@ -12240,6 +12221,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
 			continue;
 		}
 
+		if (!ctx_access)
+			continue;
+
 		switch (env->insn_aux_data[i + delta].ptr_type) {
 		case PTR_TO_CTX:
 			if (!ops->convert_ctx_access)
@@ -13093,37 +13077,6 @@ static void free_states(struct bpf_verifier_env *env)
 	}
 }
 
-/* The verifier is using insn_aux_data[] to store temporary data during
- * verification and to store information for passes that run after the
- * verification like dead code sanitization. do_check_common() for subprogram N
- * may analyze many other subprograms. sanitize_insn_aux_data() clears all
- * temporary data after do_check_common() finds that subprogram N cannot be
- * verified independently. pass_cnt counts the number of times
- * do_check_common() was run and insn->aux->seen tells the pass number
- * insn_aux_data was touched. These variables are compared to clear temporary
- * data from failed pass. For testing and experiments do_check_common() can be
- * run multiple times even when prior attempt to verify is unsuccessful.
- *
- * Note that special handling is needed on !env->bypass_spec_v1 if this is
- * ever called outside of error path with subsequent program rejection.
- */
-static void sanitize_insn_aux_data(struct bpf_verifier_env *env)
-{
-	struct bpf_insn *insn = env->prog->insnsi;
-	struct bpf_insn_aux_data *aux;
-	int i, class;
-
-	for (i = 0; i < env->prog->len; i++) {
-		class = BPF_CLASS(insn[i].code);
-		if (class != BPF_LDX && class != BPF_STX)
-			continue;
-		aux = &env->insn_aux_data[i];
-		if (aux->seen != env->pass_cnt)
-			continue;
-		memset(aux, 0, offsetof(typeof(*aux), orig_idx));
-	}
-}
-
 static int do_check_common(struct bpf_verifier_env *env, int subprog)
 {
 	bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
@@ -13200,9 +13153,6 @@ out:
 	if (!ret && pop_log)
 		bpf_vlog_reset(&env->log, 0);
 	free_states(env);
-	if (ret)
-		/* clean aux data in case subprog was rejected */
-		sanitize_insn_aux_data(env);
 	return ret;
 }