Revert "bpf: Fix pointer arithmetic mask tightening under state pruning"

ANBZ: torvalds#342

This reverts commit a4409d1.

Signed-off-by: Qiao Ma <[email protected]>
Acked-by: Mao Wenan <[email protected]>
Acked-by: Tony Lu <[email protected]>

Author: shiloong

include/linux/bpf_verifier.h

@@ -215,7 +215,6 @@ struct bpf_verifier_env {
 	struct bpf_map *used_maps[MAX_USED_MAPS]; /* array of map's used by eBPF program */
 	u32 used_map_cnt;		/* number of used maps */
 	u32 id_gen;			/* used to generate unique reg IDs */
-	bool explore_alu_limits;
 	bool allow_ptr_leaks;
 	bool seen_direct_write;
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */

kernel/bpf/verifier.c

@@ -2848,12 +2848,6 @@ 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);
@@ -4784,8 +4778,8 @@ static bool check_ids(u32 old_id, u32 cur_id, struct bpf_id_pair *idmap)
 }
 
 /* Returns true if (rold safe implies rcur safe) */
-static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
-		    struct bpf_reg_state *rcur, struct bpf_id_pair *idmap)
+static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
+		    struct bpf_id_pair *idmap)
 {
 	bool equal;
 
@@ -4811,8 +4805,6 @@ static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
 		return false;
 	switch (rold->type) {
 	case SCALAR_VALUE:
-		if (env->explore_alu_limits)
-			return false;
 		if (rcur->type == SCALAR_VALUE) {
 			/* new val must satisfy old val knowledge */
 			return range_within(rold, rcur) &&
@@ -4889,8 +4881,9 @@ static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold,
 	return false;
 }
 
-static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old,
-		      struct bpf_func_state *cur, struct bpf_id_pair *idmap)
+static bool stacksafe(struct bpf_func_state *old,
+		      struct bpf_func_state *cur,
+		      struct bpf_id_pair *idmap)
 {
 	int i, spi;
 
@@ -4932,8 +4925,9 @@ static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old,
 			continue;
 		if (old->stack[spi].slot_type[0] != STACK_SPILL)
 			continue;
-		if (!regsafe(env, &old->stack[spi].spilled_ptr,
-			     &cur->stack[spi].spilled_ptr, idmap))
+		if (!regsafe(&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.
@@ -4982,11 +4976,10 @@ 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(env, &old->regs[i], &cur->regs[i],
-			     env->idmap_scratch))
+		if (!regsafe(&old->regs[i], &cur->regs[i], env->idmap_scratch))
 			return false;
 
-	if (!stacksafe(env, old, cur, env->idmap_scratch))
+	if (!stacksafe(old, cur, env->idmap_scratch))
 		return false;
 
 	return true;