Arnd Bergmann reported an issue ([1]) where clang compiler (less than
llvm18) may trigger an error where the stack frame size exceeds the limit.
I can reproduce the error like below:
kernel/bpf/verifier.c:24491:5: error: stack frame size (2552) exceeds limit (1280) in 'bpf_check'
[-Werror,-Wframe-larger-than]
kernel/bpf/verifier.c:19921:12: error: stack frame size (1368) exceeds limit (1280) in 'do_check'
[-Werror,-Wframe-larger-than]
Use env->insn_buf for bpf insns instead of putting these insns on the
stack. This can resolve the above 'bpf_check' error. The 'do_check' error
will be resolved in the next patch.
[1] https://lore.kernel.org/bpf/20250620113846.3950478-1-arnd@xxxxxxxxxx/
Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
kernel/bpf/verifier.c | 194 ++++++++++++++++++++----------------------
1 file changed, 91 insertions(+), 103 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 90e688f81a48..29faef51065d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -20939,26 +20939,27 @@ static bool insn_is_cond_jump(u8 code)
static void opt_hard_wire_dead_code_branches(struct bpf_verifier_env *env)
{
struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
- struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
+ struct bpf_insn *ja = env->insn_buf;
struct bpf_insn *insn = env->prog->insnsi;
const int insn_cnt = env->prog->len;
int i;
+ *ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
for (i = 0; i < insn_cnt; i++, insn++) {
if (!insn_is_cond_jump(insn->code))
continue;
if (!aux_data[i + 1].seen)
- ja.off = insn->off;
+ ja->off = insn->off;
else if (!aux_data[i + 1 + insn->off].seen)
- ja.off = 0;
+ ja->off = 0;
else
continue;
if (bpf_prog_is_offloaded(env->prog->aux))
- bpf_prog_offload_replace_insn(env, i, &ja);
+ bpf_prog_offload_replace_insn(env, i, ja);
- memcpy(insn, &ja, sizeof(ja));
+ memcpy(insn, ja, sizeof(*ja));
}
}
@@ -21017,7 +21018,9 @@ static int opt_remove_nops(struct bpf_verifier_env *env)
static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
const union bpf_attr *attr)
{
- struct bpf_insn *patch, zext_patch[2], rnd_hi32_patch[4];
+ struct bpf_insn *patch;
+ struct bpf_insn *zext_patch = env->insn_buf;
+ struct bpf_insn *rnd_hi32_patch = &env->insn_buf[2];
struct bpf_insn_aux_data *aux = env->insn_aux_data;
int i, patch_len, delta = 0, len = env->prog->len;
struct bpf_insn *insns = env->prog->insnsi;
@@ -21195,13 +21198,12 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
if (env->insn_aux_data[i + delta].nospec) {
WARN_ON_ONCE(env->insn_aux_data[i + delta].alu_state);
- struct bpf_insn patch[] = {
- BPF_ST_NOSPEC(),
- *insn,
- };
+ struct bpf_insn *patch = &insn_buf[0];
- cnt = ARRAY_SIZE(patch);
- new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
+ *patch++ = BPF_ST_NOSPEC();
+ *patch++ = *insn;
+ cnt = patch - insn_buf;
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
@@ -21269,13 +21271,12 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
/* nospec_result is only used to mitigate Spectre v4 and
* to limit verification-time for Spectre v1.
*/
- struct bpf_insn patch[] = {
- *insn,
- BPF_ST_NOSPEC(),
- };
+ struct bpf_insn *patch = &insn_buf[0];
- cnt = ARRAY_SIZE(patch);
- new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
+ *patch++ = *insn;
+ *patch++ = BPF_ST_NOSPEC();
+ cnt = patch - insn_buf;
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
@@ -21945,13 +21946,12 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
u16 stack_depth_extra = 0;
if (env->seen_exception && !env->exception_callback_subprog) {
- struct bpf_insn patch[] = {
- env->prog->insnsi[insn_cnt - 1],
- BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
- BPF_EXIT_INSN(),
- };
+ struct bpf_insn *patch = &insn_buf[0];
- ret = add_hidden_subprog(env, patch, ARRAY_SIZE(patch));
+ *patch++ = env->prog->insnsi[insn_cnt - 1];
+ *patch++ = BPF_MOV64_REG(BPF_REG_0, BPF_REG_1);
+ *patch++ = BPF_EXIT_INSN();
+ ret = add_hidden_subprog(env, insn_buf, patch - insn_buf);
if (ret < 0)
return ret;
prog = env->prog;
@@ -21987,20 +21987,18 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
insn->off == 1 && insn->imm == -1) {
bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
bool isdiv = BPF_OP(insn->code) == BPF_DIV;
- struct bpf_insn *patchlet;
- struct bpf_insn chk_and_sdiv[] = {
- BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
- BPF_NEG | BPF_K, insn->dst_reg,
- 0, 0, 0),
- };
- struct bpf_insn chk_and_smod[] = {
- BPF_MOV32_IMM(insn->dst_reg, 0),
- };
+ struct bpf_insn *patch = &insn_buf[0];
+
+ if (isdiv)
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
+ BPF_NEG | BPF_K, insn->dst_reg,
+ 0, 0, 0);
+ else
+ *patch++ = BPF_MOV32_IMM(insn->dst_reg, 0);
- patchlet = isdiv ? chk_and_sdiv : chk_and_smod;
- cnt = isdiv ? ARRAY_SIZE(chk_and_sdiv) : ARRAY_SIZE(chk_and_smod);
+ cnt = patch - insn_buf;
- new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
@@ -22019,83 +22017,73 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
bool isdiv = BPF_OP(insn->code) == BPF_DIV;
bool is_sdiv = isdiv && insn->off == 1;
bool is_smod = !isdiv && insn->off == 1;
- struct bpf_insn *patchlet;
- struct bpf_insn chk_and_div[] = {
- /* [R,W]x div 0 -> 0 */
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JNE | BPF_K, insn->src_reg,
- 0, 2, 0),
- BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg),
- BPF_JMP_IMM(BPF_JA, 0, 0, 1),
- *insn,
- };
- struct bpf_insn chk_and_mod[] = {
- /* [R,W]x mod 0 -> [R,W]x */
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JEQ | BPF_K, insn->src_reg,
- 0, 1 + (is64 ? 0 : 1), 0),
- *insn,
- BPF_JMP_IMM(BPF_JA, 0, 0, 1),
- BPF_MOV32_REG(insn->dst_reg, insn->dst_reg),
- };
- struct bpf_insn chk_and_sdiv[] = {
+ struct bpf_insn *patch = &insn_buf[0];
+
+ if (is_sdiv) {
/* [R,W]x sdiv 0 -> 0
* LLONG_MIN sdiv -1 -> LLONG_MIN
* INT_MIN sdiv -1 -> INT_MIN
*/
- BPF_MOV64_REG(BPF_REG_AX, insn->src_reg),
- BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
- BPF_ADD | BPF_K, BPF_REG_AX,
- 0, 0, 1),
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JGT | BPF_K, BPF_REG_AX,
- 0, 4, 1),
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JEQ | BPF_K, BPF_REG_AX,
- 0, 1, 0),
- BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
- BPF_MOV | BPF_K, insn->dst_reg,
- 0, 0, 0),
+ *patch++ = BPF_MOV64_REG(BPF_REG_AX, insn->src_reg);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
+ BPF_ADD | BPF_K, BPF_REG_AX,
+ 0, 0, 1);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JGT | BPF_K, BPF_REG_AX,
+ 0, 4, 1);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JEQ | BPF_K, BPF_REG_AX,
+ 0, 1, 0);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
+ BPF_MOV | BPF_K, insn->dst_reg,
+ 0, 0, 0);
/* BPF_NEG(LLONG_MIN) == -LLONG_MIN == LLONG_MIN */
- BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
- BPF_NEG | BPF_K, insn->dst_reg,
- 0, 0, 0),
- BPF_JMP_IMM(BPF_JA, 0, 0, 1),
- *insn,
- };
- struct bpf_insn chk_and_smod[] = {
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
+ BPF_NEG | BPF_K, insn->dst_reg,
+ 0, 0, 0);
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = *insn;
+ cnt = patch - insn_buf;
+ } else if (is_smod) {
/* [R,W]x mod 0 -> [R,W]x */
/* [R,W]x mod -1 -> 0 */
- BPF_MOV64_REG(BPF_REG_AX, insn->src_reg),
- BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
- BPF_ADD | BPF_K, BPF_REG_AX,
- 0, 0, 1),
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JGT | BPF_K, BPF_REG_AX,
- 0, 3, 1),
- BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
- BPF_JEQ | BPF_K, BPF_REG_AX,
- 0, 3 + (is64 ? 0 : 1), 1),
- BPF_MOV32_IMM(insn->dst_reg, 0),
- BPF_JMP_IMM(BPF_JA, 0, 0, 1),
- *insn,
- BPF_JMP_IMM(BPF_JA, 0, 0, 1),
- BPF_MOV32_REG(insn->dst_reg, insn->dst_reg),
- };
-
- if (is_sdiv) {
- patchlet = chk_and_sdiv;
- cnt = ARRAY_SIZE(chk_and_sdiv);
- } else if (is_smod) {
- patchlet = chk_and_smod;
- cnt = ARRAY_SIZE(chk_and_smod) - (is64 ? 2 : 0);
+ *patch++ = BPF_MOV64_REG(BPF_REG_AX, insn->src_reg);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
+ BPF_ADD | BPF_K, BPF_REG_AX,
+ 0, 0, 1);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JGT | BPF_K, BPF_REG_AX,
+ 0, 3, 1);
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JEQ | BPF_K, BPF_REG_AX,
+ 0, 3 + (is64 ? 0 : 1), 1);
+ *patch++ = BPF_MOV32_IMM(insn->dst_reg, 0);
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = *insn;
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
+ cnt = (patch - insn_buf) - (is64 ? 2 : 0);
+ } else if (isdiv) {
+ /* [R,W]x div 0 -> 0 */
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JNE | BPF_K, insn->src_reg,
+ 0, 2, 0);
+ *patch++ = BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg);
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = *insn;
+ cnt = patch - insn_buf;
} else {
- patchlet = isdiv ? chk_and_div : chk_and_mod;
- cnt = isdiv ? ARRAY_SIZE(chk_and_div) :
- ARRAY_SIZE(chk_and_mod) - (is64 ? 2 : 0);
+ /* [R,W]x mod 0 -> [R,W]x */
+ *patch++ = BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
+ BPF_JEQ | BPF_K, insn->src_reg,
+ 0, 1 + (is64 ? 0 : 1), 0);
+ *patch++ = *insn;
+ *patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
+ *patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
+ cnt = (patch - insn_buf) - (is64 ? 2 : 0);
}
- new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
+ new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
if (!new_prog)
return -ENOMEM;
--
2.47.1
