1 files changed, 57 insertions, 44 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9f81818f2941..b6a1f7c14a67 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -153,22 +153,19 @@ struct reg_state {
 
 enum bpf_stack_slot_type {
 	STACK_INVALID,    /* nothing was stored in this stack slot */
-	STACK_SPILL,      /* 1st byte of register spilled into stack */
-	STACK_SPILL_PART, /* other 7 bytes of register spill */
+	STACK_SPILL,      /* register spilled into stack */
 	STACK_MISC	  /* BPF program wrote some data into this slot */
 };
 
-struct bpf_stack_slot {
-	enum bpf_stack_slot_type stype;
-	struct reg_state reg_st;
-};
+#define BPF_REG_SIZE 8	/* size of eBPF register in bytes */
 
 /* state of the program:
  * type of all registers and stack info
  */
 struct verifier_state {
 	struct reg_state regs[MAX_BPF_REG];
-	struct bpf_stack_slot stack[MAX_BPF_STACK];
+	u8 stack_slot_type[MAX_BPF_STACK];
+	struct reg_state spilled_regs[MAX_BPF_STACK / BPF_REG_SIZE];
 };
 
 /* linked list of verifier states used to prune search */
@@ -259,10 +256,10 @@ static void print_verifier_state(struct verifier_env *env)
 				env->cur_state.regs[i].map_ptr->key_size,
 				env->cur_state.regs[i].map_ptr->value_size);
 	}
-	for (i = 0; i < MAX_BPF_STACK; i++) {
-		if (env->cur_state.stack[i].stype == STACK_SPILL)
+	for (i = 0; i < MAX_BPF_STACK; i += BPF_REG_SIZE) {
+		if (env->cur_state.stack_slot_type[i] == STACK_SPILL)
 			verbose(" fp%d=%s", -MAX_BPF_STACK + i,
-				reg_type_str[env->cur_state.stack[i].reg_st.type]);
+				reg_type_str[env->cur_state.spilled_regs[i / BPF_REG_SIZE].type]);
 	}
 	verbose("\n");
 }
@@ -539,8 +536,10 @@ static int bpf_size_to_bytes(int bpf_size)
 static int check_stack_write(struct verifier_state *state, int off, int size,
 			     int value_regno)
 {
-	struct bpf_stack_slot *slot;
 	int i;
+	/* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
+	 * so it's aligned access and [off, off + size) are within stack limits
+	 */
 
 	if (value_regno >= 0 &&
 	    (state->regs[value_regno].type == PTR_TO_MAP_VALUE ||
@@ -548,30 +547,24 @@ static int check_stack_write(struct verifier_state *state, int off, int size,
 	     state->regs[value_regno].type == PTR_TO_CTX)) {
 
 		/* register containing pointer is being spilled into stack */
-		if (size != 8) {
+		if (size != BPF_REG_SIZE) {
 			verbose("invalid size of register spill\n");
 			return -EACCES;
 		}
 
-		slot = &state->stack[MAX_BPF_STACK + off];
-		slot->stype = STACK_SPILL;
 		/* save register state */
-		slot->reg_st = state->regs[value_regno];
-		for (i = 1; i < 8; i++) {
-			slot = &state->stack[MAX_BPF_STACK + off + i];
-			slot->stype = STACK_SPILL_PART;
-			slot->reg_st.type = UNKNOWN_VALUE;
-			slot->reg_st.map_ptr = NULL;
-		}
-	} else {
+		state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
+			state->regs[value_regno];
 
+		for (i = 0; i < BPF_REG_SIZE; i++)
+			state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_SPILL;
+	} else {
 		/* regular write of data into stack */
-		for (i = 0; i < size; i++) {
-			slot = &state->stack[MAX_BPF_STACK + off + i];
-			slot->stype = STACK_MISC;
-			slot->reg_st.type = UNKNOWN_VALUE;
-			slot->reg_st.map_ptr = NULL;
-		}
+		state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE] =
+			(struct reg_state) {};
+
+		for (i = 0; i < size; i++)
+			state->stack_slot_type[MAX_BPF_STACK + off + i] = STACK_MISC;
 	}
 	return 0;
 }
@@ -579,19 +572,18 @@ static int check_stack_write(struct verifier_state *state, int off, int size,
 static int check_stack_read(struct verifier_state *state, int off, int size,
 			    int value_regno)
 {
+	u8 *slot_type;
 	int i;
-	struct bpf_stack_slot *slot;
 
-	slot = &state->stack[MAX_BPF_STACK + off];
+	slot_type = &state->stack_slot_type[MAX_BPF_STACK + off];
 
-	if (slot->stype == STACK_SPILL) {
-		if (size != 8) {
+	if (slot_type[0] == STACK_SPILL) {
+		if (size != BPF_REG_SIZE) {
 			verbose("invalid size of register spill\n");
 			return -EACCES;
 		}
-		for (i = 1; i < 8; i++) {
-			if (state->stack[MAX_BPF_STACK + off + i].stype !=
-			    STACK_SPILL_PART) {
+		for (i = 1; i < BPF_REG_SIZE; i++) {
+			if (slot_type[i] != STACK_SPILL) {
 				verbose("corrupted spill memory\n");
 				return -EACCES;
 			}
@@ -599,12 +591,12 @@ static int check_stack_read(struct verifier_state *state, int off, int size,
 
 		if (value_regno >= 0)
 			/* restore register state from stack */
-			state->regs[value_regno] = slot->reg_st;
+			state->regs[value_regno] =
+				state->spilled_regs[(MAX_BPF_STACK + off) / BPF_REG_SIZE];
 		return 0;
 	} else {
 		for (i = 0; i < size; i++) {
-			if (state->stack[MAX_BPF_STACK + off + i].stype !=
-			    STACK_MISC) {
+			if (slot_type[i] != STACK_MISC) {
 				verbose("invalid read from stack off %d+%d size %d\n",
 					off, i, size);
 				return -EACCES;
@@ -747,7 +739,7 @@ static int check_stack_boundary(struct verifier_env *env,
 	}
 
 	for (i = 0; i < access_size; i++) {
-		if (state->stack[MAX_BPF_STACK + off + i].stype != STACK_MISC) {
+		if (state->stack_slot_type[MAX_BPF_STACK + off + i] != STACK_MISC) {
 			verbose("invalid indirect read from stack off %d+%d size %d\n",
 				off, i, access_size);
 			return -EACCES;
@@ -1417,12 +1409,33 @@ static bool states_equal(struct verifier_state *old, struct verifier_state *cur)
 	}
 
 	for (i = 0; i < MAX_BPF_STACK; i++) {
-		if (memcmp(&old->stack[i], &cur->stack[i],
-			   sizeof(old->stack[0])) != 0) {
-			if (old->stack[i].stype == STACK_INVALID)
-				continue;
+		if (old->stack_slot_type[i] == STACK_INVALID)
+			continue;
+		if (old->stack_slot_type[i] != cur->stack_slot_type[i])
+			/* Ex: old explored (safe) state has STACK_SPILL in
+			 * this stack slot, but current has has STACK_MISC ->
+			 * this verifier states are not equivalent,
+			 * return false to continue verification of this path
+			 */
 			return false;
-		}
+		if (i % BPF_REG_SIZE)
+			continue;
+		if (memcmp(&old->spilled_regs[i / BPF_REG_SIZE],
+			   &cur->spilled_regs[i / BPF_REG_SIZE],
+			   sizeof(old->spilled_regs[0])))
+			/* when explored and current stack slot types are
+			 * the same, check that stored pointers types
+			 * are the same as well.
+			 * Ex: explored safe path could have stored
+			 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -8}
+			 * but current path has stored:
+			 * (struct reg_state) {.type = PTR_TO_STACK, .imm = -16}
+			 * such verifier states are not equivalent.
+			 * return false to continue verification of this path
+			 */
+			return false;
+		else
+			continue;
 	}
 	return true;
 }