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Message-ID: <20250224203619.594724-3-luis.gerhorst@fau.de>
Date: Mon, 24 Feb 2025 21:36:12 +0100
From: Luis Gerhorst <luis.gerhorst@....de>
To: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Eduard Zingerman <eddyz87@...il.com>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...ichev.me>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
Puranjay Mohan <puranjay@...nel.org>,
Xu Kuohai <xukuohai@...weicloud.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mykola Lysenko <mykolal@...com>,
Shuah Khan <shuah@...nel.org>,
Luis Gerhorst <luis.gerhorst@....de>,
Henriette Herzog <henriette.herzog@....de>,
Cupertino Miranda <cupertino.miranda@...cle.com>,
Matan Shachnai <m.shachnai@...il.com>,
Dimitar Kanaliev <dimitar.kanaliev@...eground.com>,
Shung-Hsi Yu <shung-hsi.yu@...e.com>,
Daniel Xu <dxu@...uu.xyz>,
bpf@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org
Cc: Maximilian Ott <ott@...fau.de>,
Milan Stephan <milan.stephan@....de>
Subject: [RFC PATCH 2/9] bpf: Refactor do_check() if/else into do_check_insn()
This is required to catch the errors later and fall back to a nospec if
on a speculative path.
Move code into do_check_insn(), replace
"continue" with "return CHECK_NEXT_INSN",
"break" with "return ALL_PATHS_CHECKED",
"do_print_state = " with "*do_print_state = ",
and "goto process_bpf_exit" / fallthrough with "return process_bpf_exit()".
Signed-off-by: Luis Gerhorst <luis.gerhorst@....de>
Acked-by: Henriette Herzog <henriette.herzog@....de>
Cc: Maximilian Ott <ott@...fau.de>
Cc: Milan Stephan <milan.stephan@....de>
---
kernel/bpf/verifier.c | 528 +++++++++++++++++++++++-------------------
1 file changed, 288 insertions(+), 240 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5be3bd38f540..42ff90bc81e6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18932,6 +18932,275 @@ static int save_aux_ptr_type(struct bpf_verifier_env *env, enum bpf_reg_type typ
return 0;
}
+enum {
+ ALL_PATHS_CHECKED = 1,
+ CHECK_NEXT_INSN
+};
+
+static int process_bpf_exit(struct bpf_verifier_env *env, int *prev_insn_idx,
+ bool pop_log, bool *do_print_state)
+{
+ int err;
+
+ mark_verifier_state_scratched(env);
+ update_branch_counts(env, env->cur_state);
+ err = pop_stack(env, prev_insn_idx,
+ &env->insn_idx, pop_log);
+ if (err < 0) {
+ if (err != -ENOENT)
+ return err;
+ return ALL_PATHS_CHECKED;
+ }
+
+ *do_print_state = true;
+ return CHECK_NEXT_INSN;
+}
+
+static int do_check_insn(struct bpf_verifier_env *env, struct bpf_insn *insn,
+ bool pop_log, bool *do_print_state,
+ struct bpf_reg_state *regs,
+ struct bpf_verifier_state *state, int *prev_insn_idx)
+{
+ int err;
+ u8 class = BPF_CLASS(insn->code);
+ bool exception_exit = false;
+
+ if (class == BPF_ALU || class == BPF_ALU64) {
+ err = check_alu_op(env, insn);
+ if (err)
+ return err;
+
+ } else if (class == BPF_LDX) {
+ enum bpf_reg_type src_reg_type;
+
+ /* check for reserved fields is already done */
+
+ /* check src operand */
+ err = check_reg_arg(env, insn->src_reg, SRC_OP);
+ if (err)
+ return err;
+
+ err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
+ if (err)
+ return err;
+
+ src_reg_type = regs[insn->src_reg].type;
+
+ /* check that memory (src_reg + off) is readable,
+ * the state of dst_reg will be updated by this func
+ */
+ err = check_mem_access(env, env->insn_idx, insn->src_reg,
+ insn->off, BPF_SIZE(insn->code),
+ BPF_READ, insn->dst_reg, false,
+ BPF_MODE(insn->code) == BPF_MEMSX);
+ err = err ?: save_aux_ptr_type(env, src_reg_type, true);
+ err = err ?:
+ reg_bounds_sanity_check(env, ®s[insn->dst_reg],
+ "ldx");
+ if (err)
+ return err;
+ } else if (class == BPF_STX) {
+ enum bpf_reg_type dst_reg_type;
+
+ if (BPF_MODE(insn->code) == BPF_ATOMIC) {
+ err = check_atomic(env, env->insn_idx, insn);
+ if (err)
+ return err;
+ env->insn_idx++;
+ return CHECK_NEXT_INSN;
+ }
+
+ if (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0) {
+ verbose(env, "BPF_STX uses reserved fields\n");
+ return -EINVAL;
+ }
+
+ /* check src1 operand */
+ err = check_reg_arg(env, insn->src_reg, SRC_OP);
+ if (err)
+ return err;
+ /* check src2 operand */
+ err = check_reg_arg(env, insn->dst_reg, SRC_OP);
+ if (err)
+ return err;
+
+ dst_reg_type = regs[insn->dst_reg].type;
+
+ /* check that memory (dst_reg + off) is writeable */
+ err = check_mem_access(env, env->insn_idx, insn->dst_reg,
+ insn->off, BPF_SIZE(insn->code),
+ BPF_WRITE, insn->src_reg, false, false);
+ if (err)
+ return err;
+
+ err = save_aux_ptr_type(env, dst_reg_type, false);
+ if (err)
+ return err;
+ } else if (class == BPF_ST) {
+ enum bpf_reg_type dst_reg_type;
+
+ if (BPF_MODE(insn->code) != BPF_MEM ||
+ insn->src_reg != BPF_REG_0) {
+ verbose(env, "BPF_ST uses reserved fields\n");
+ return -EINVAL;
+ }
+ /* check src operand */
+ err = check_reg_arg(env, insn->dst_reg, SRC_OP);
+ if (err)
+ return err;
+
+ dst_reg_type = regs[insn->dst_reg].type;
+
+ /* check that memory (dst_reg + off) is writeable */
+ err = check_mem_access(env, env->insn_idx, insn->dst_reg,
+ insn->off, BPF_SIZE(insn->code),
+ BPF_WRITE, -1, false, false);
+ if (err)
+ return err;
+
+ err = save_aux_ptr_type(env, dst_reg_type, false);
+ if (err)
+ return err;
+ } else if (class == BPF_JMP || class == BPF_JMP32) {
+ u8 opcode = BPF_OP(insn->code);
+
+ env->jmps_processed++;
+ if (opcode == BPF_CALL) {
+ if (BPF_SRC(insn->code) != BPF_K ||
+ (insn->src_reg != BPF_PSEUDO_KFUNC_CALL &&
+ insn->off != 0) ||
+ (insn->src_reg != BPF_REG_0 &&
+ insn->src_reg != BPF_PSEUDO_CALL &&
+ insn->src_reg != BPF_PSEUDO_KFUNC_CALL) ||
+ insn->dst_reg != BPF_REG_0 || class == BPF_JMP32) {
+ verbose(env, "BPF_CALL uses reserved fields\n");
+ return -EINVAL;
+ }
+
+ if (env->cur_state->active_locks) {
+ if ((insn->src_reg == BPF_REG_0 &&
+ insn->imm != BPF_FUNC_spin_unlock) ||
+ (insn->src_reg == BPF_PSEUDO_KFUNC_CALL &&
+ (insn->off != 0 ||
+ !kfunc_spin_allowed(insn->imm)))) {
+ verbose(env,
+ "function calls are not allowed while holding a lock\n");
+ return -EINVAL;
+ }
+ }
+ if (insn->src_reg == BPF_PSEUDO_CALL) {
+ err = check_func_call(env, insn,
+ &env->insn_idx);
+ } else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
+ err = check_kfunc_call(env, insn,
+ &env->insn_idx);
+ if (!err && is_bpf_throw_kfunc(insn)) {
+ exception_exit = true;
+ goto process_bpf_exit_full;
+ }
+ } else {
+ err = check_helper_call(env, insn,
+ &env->insn_idx);
+ }
+ if (err)
+ return err;
+
+ mark_reg_scratched(env, BPF_REG_0);
+ } else if (opcode == BPF_JA) {
+ if (BPF_SRC(insn->code) != BPF_K ||
+ insn->src_reg != BPF_REG_0 ||
+ insn->dst_reg != BPF_REG_0 ||
+ (class == BPF_JMP && insn->imm != 0) ||
+ (class == BPF_JMP32 && insn->off != 0)) {
+ verbose(env, "BPF_JA uses reserved fields\n");
+ return -EINVAL;
+ }
+
+ if (class == BPF_JMP)
+ env->insn_idx += insn->off + 1;
+ else
+ env->insn_idx += insn->imm + 1;
+ return CHECK_NEXT_INSN;
+
+ } else if (opcode == BPF_EXIT) {
+ if (BPF_SRC(insn->code) != BPF_K || insn->imm != 0 ||
+ insn->src_reg != BPF_REG_0 ||
+ insn->dst_reg != BPF_REG_0 || class == BPF_JMP32) {
+ verbose(env, "BPF_EXIT uses reserved fields\n");
+ return -EINVAL;
+ }
+process_bpf_exit_full:
+ /* We must do check_reference_leak here before
+ * prepare_func_exit to handle the case when
+ * state->curframe > 0, it may be a callback function,
+ * for which reference_state must match caller reference
+ * state when it exits.
+ */
+ err = check_resource_leak(env, exception_exit,
+ !env->cur_state->curframe,
+ "BPF_EXIT instruction in main prog");
+ if (err)
+ return err;
+
+ /* The side effect of the prepare_func_exit which is
+ * being skipped is that it frees bpf_func_state.
+ * Typically, process_bpf_exit will only be hit with
+ * outermost exit. copy_verifier_state in pop_stack will
+ * handle freeing of any extra bpf_func_state left over
+ * from not processing all nested function exits. We
+ * also skip return code checks as they are not needed
+ * for exceptional exits.
+ */
+ if (exception_exit)
+ goto process_bpf_exit;
+
+ if (state->curframe) {
+ /* exit from nested function */
+ err = prepare_func_exit(env, &env->insn_idx);
+ if (err)
+ return err;
+ *do_print_state = true;
+ return CHECK_NEXT_INSN;
+ }
+
+ err = check_return_code(env, BPF_REG_0, "R0");
+ if (err)
+ return err;
+process_bpf_exit:
+ return process_bpf_exit(env, prev_insn_idx, pop_log,
+ do_print_state);
+ } else {
+ err = check_cond_jmp_op(env, insn, &env->insn_idx);
+ if (err)
+ return err;
+ }
+ } else if (class == BPF_LD) {
+ u8 mode = BPF_MODE(insn->code);
+
+ if (mode == BPF_ABS || mode == BPF_IND) {
+ err = check_ld_abs(env, insn);
+ if (err)
+ return err;
+
+ } else if (mode == BPF_IMM) {
+ err = check_ld_imm(env, insn);
+ if (err)
+ return err;
+
+ env->insn_idx++;
+ sanitize_mark_insn_seen(env);
+ } else {
+ verbose(env, "invalid BPF_LD mode\n");
+ return -EINVAL;
+ }
+ } else {
+ verbose(env, "unknown insn class %d\n", class);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
static int do_check(struct bpf_verifier_env *env)
{
bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
@@ -18943,9 +19212,7 @@ static int do_check(struct bpf_verifier_env *env)
int prev_insn_idx = -1;
for (;;) {
- bool exception_exit = false;
struct bpf_insn *insn;
- u8 class;
int err;
/* reset current history entry on each new instruction */
@@ -18959,7 +19226,6 @@ static int do_check(struct bpf_verifier_env *env)
}
insn = &insns[env->insn_idx];
- class = BPF_CLASS(insn->code);
if (++env->insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
verbose(env,
@@ -18985,7 +19251,16 @@ static int do_check(struct bpf_verifier_env *env)
else
verbose(env, "%d: safe\n", env->insn_idx);
}
- goto process_bpf_exit;
+ err = process_bpf_exit(env, &prev_insn_idx, pop_log,
+ &do_print_state);
+ if (err == CHECK_NEXT_INSN) {
+ continue;
+ } else if (err == ALL_PATHS_CHECKED) {
+ break;
+ } else if (err) {
+ WARN_ON_ONCE(err > 0);
+ return err;
+ }
}
}
@@ -19039,242 +19314,15 @@ static int do_check(struct bpf_verifier_env *env)
sanitize_mark_insn_seen(env);
prev_insn_idx = env->insn_idx;
- if (class == BPF_ALU || class == BPF_ALU64) {
- err = check_alu_op(env, insn);
- if (err)
- return err;
-
- } else if (class == BPF_LDX) {
- enum bpf_reg_type src_reg_type;
-
- /* check for reserved fields is already done */
-
- /* check src operand */
- err = check_reg_arg(env, insn->src_reg, SRC_OP);
- if (err)
- return err;
-
- err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
- if (err)
- return err;
-
- src_reg_type = regs[insn->src_reg].type;
-
- /* check that memory (src_reg + off) is readable,
- * the state of dst_reg will be updated by this func
- */
- err = check_mem_access(env, env->insn_idx, insn->src_reg,
- insn->off, BPF_SIZE(insn->code),
- BPF_READ, insn->dst_reg, false,
- BPF_MODE(insn->code) == BPF_MEMSX);
- err = err ?: save_aux_ptr_type(env, src_reg_type, true);
- err = err ?: reg_bounds_sanity_check(env, ®s[insn->dst_reg], "ldx");
- if (err)
- return err;
- } else if (class == BPF_STX) {
- enum bpf_reg_type dst_reg_type;
-
- if (BPF_MODE(insn->code) == BPF_ATOMIC) {
- err = check_atomic(env, env->insn_idx, insn);
- if (err)
- return err;
- env->insn_idx++;
- continue;
- }
-
- if (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0) {
- verbose(env, "BPF_STX uses reserved fields\n");
- return -EINVAL;
- }
-
- /* check src1 operand */
- err = check_reg_arg(env, insn->src_reg, SRC_OP);
- if (err)
- return err;
- /* check src2 operand */
- err = check_reg_arg(env, insn->dst_reg, SRC_OP);
- if (err)
- return err;
-
- dst_reg_type = regs[insn->dst_reg].type;
-
- /* check that memory (dst_reg + off) is writeable */
- err = check_mem_access(env, env->insn_idx, insn->dst_reg,
- insn->off, BPF_SIZE(insn->code),
- BPF_WRITE, insn->src_reg, false, false);
- if (err)
- return err;
-
- err = save_aux_ptr_type(env, dst_reg_type, false);
- if (err)
- return err;
- } else if (class == BPF_ST) {
- enum bpf_reg_type dst_reg_type;
-
- if (BPF_MODE(insn->code) != BPF_MEM ||
- insn->src_reg != BPF_REG_0) {
- verbose(env, "BPF_ST uses reserved fields\n");
- return -EINVAL;
- }
- /* check src operand */
- err = check_reg_arg(env, insn->dst_reg, SRC_OP);
- if (err)
- return err;
-
- dst_reg_type = regs[insn->dst_reg].type;
-
- /* check that memory (dst_reg + off) is writeable */
- err = check_mem_access(env, env->insn_idx, insn->dst_reg,
- insn->off, BPF_SIZE(insn->code),
- BPF_WRITE, -1, false, false);
- if (err)
- return err;
-
- err = save_aux_ptr_type(env, dst_reg_type, false);
- if (err)
- return err;
- } else if (class == BPF_JMP || class == BPF_JMP32) {
- u8 opcode = BPF_OP(insn->code);
-
- env->jmps_processed++;
- if (opcode == BPF_CALL) {
- if (BPF_SRC(insn->code) != BPF_K ||
- (insn->src_reg != BPF_PSEUDO_KFUNC_CALL
- && insn->off != 0) ||
- (insn->src_reg != BPF_REG_0 &&
- insn->src_reg != BPF_PSEUDO_CALL &&
- insn->src_reg != BPF_PSEUDO_KFUNC_CALL) ||
- insn->dst_reg != BPF_REG_0 ||
- class == BPF_JMP32) {
- verbose(env, "BPF_CALL uses reserved fields\n");
- return -EINVAL;
- }
-
- if (env->cur_state->active_locks) {
- if ((insn->src_reg == BPF_REG_0 && insn->imm != BPF_FUNC_spin_unlock) ||
- (insn->src_reg == BPF_PSEUDO_KFUNC_CALL &&
- (insn->off != 0 || !kfunc_spin_allowed(insn->imm)))) {
- verbose(env, "function calls are not allowed while holding a lock\n");
- return -EINVAL;
- }
- }
- if (insn->src_reg == BPF_PSEUDO_CALL) {
- err = check_func_call(env, insn, &env->insn_idx);
- } else if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
- err = check_kfunc_call(env, insn, &env->insn_idx);
- if (!err && is_bpf_throw_kfunc(insn)) {
- exception_exit = true;
- goto process_bpf_exit_full;
- }
- } else {
- err = check_helper_call(env, insn, &env->insn_idx);
- }
- if (err)
- return err;
-
- mark_reg_scratched(env, BPF_REG_0);
- } else if (opcode == BPF_JA) {
- if (BPF_SRC(insn->code) != BPF_K ||
- insn->src_reg != BPF_REG_0 ||
- insn->dst_reg != BPF_REG_0 ||
- (class == BPF_JMP && insn->imm != 0) ||
- (class == BPF_JMP32 && insn->off != 0)) {
- verbose(env, "BPF_JA uses reserved fields\n");
- return -EINVAL;
- }
-
- if (class == BPF_JMP)
- env->insn_idx += insn->off + 1;
- else
- env->insn_idx += insn->imm + 1;
- continue;
-
- } else if (opcode == BPF_EXIT) {
- if (BPF_SRC(insn->code) != BPF_K ||
- insn->imm != 0 ||
- insn->src_reg != BPF_REG_0 ||
- insn->dst_reg != BPF_REG_0 ||
- class == BPF_JMP32) {
- verbose(env, "BPF_EXIT uses reserved fields\n");
- return -EINVAL;
- }
-process_bpf_exit_full:
- /* We must do check_reference_leak here before
- * prepare_func_exit to handle the case when
- * state->curframe > 0, it may be a callback
- * function, for which reference_state must
- * match caller reference state when it exits.
- */
- err = check_resource_leak(env, exception_exit, !env->cur_state->curframe,
- "BPF_EXIT instruction in main prog");
- if (err)
- return err;
-
- /* The side effect of the prepare_func_exit
- * which is being skipped is that it frees
- * bpf_func_state. Typically, process_bpf_exit
- * will only be hit with outermost exit.
- * copy_verifier_state in pop_stack will handle
- * freeing of any extra bpf_func_state left over
- * from not processing all nested function
- * exits. We also skip return code checks as
- * they are not needed for exceptional exits.
- */
- if (exception_exit)
- goto process_bpf_exit;
-
- if (state->curframe) {
- /* exit from nested function */
- err = prepare_func_exit(env, &env->insn_idx);
- if (err)
- return err;
- do_print_state = true;
- continue;
- }
-
- err = check_return_code(env, BPF_REG_0, "R0");
- if (err)
- return err;
-process_bpf_exit:
- mark_verifier_state_scratched(env);
- update_branch_counts(env, env->cur_state);
- err = pop_stack(env, &prev_insn_idx,
- &env->insn_idx, pop_log);
- if (err < 0) {
- if (err != -ENOENT)
- return err;
- break;
- } else {
- do_print_state = true;
- continue;
- }
- } else {
- err = check_cond_jmp_op(env, insn, &env->insn_idx);
- if (err)
- return err;
- }
- } else if (class == BPF_LD) {
- u8 mode = BPF_MODE(insn->code);
-
- if (mode == BPF_ABS || mode == BPF_IND) {
- err = check_ld_abs(env, insn);
- if (err)
- return err;
-
- } else if (mode == BPF_IMM) {
- err = check_ld_imm(env, insn);
- if (err)
- return err;
-
- env->insn_idx++;
- sanitize_mark_insn_seen(env);
- } else {
- verbose(env, "invalid BPF_LD mode\n");
- return -EINVAL;
- }
- } else {
- verbose(env, "unknown insn class %d\n", class);
- return -EINVAL;
+ err = do_check_insn(env, insn, pop_log, &do_print_state, regs, state,
+ &prev_insn_idx);
+ if (err == CHECK_NEXT_INSN) {
+ continue;
+ } else if (err == ALL_PATHS_CHECKED) {
+ break;
+ } else if (err) {
+ WARN_ON_ONCE(err > 0);
+ return err;
}
env->insn_idx++;
--
2.48.1
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