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bpf: Reduce stack frame size by using env->insn_buf for bpf insns 

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@kernel.org/

Reported-by: Arnd Bergmann <arnd@kernel.org>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20250703141111.1484521-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
pull/1309/head
Yonghong Song 2025-07-03 07:11:11 -07:00 committed by Alexei Starovoitov
parent 3b87251439
commit 45e9cd38aa
1 changed files with 91 additions and 97 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

170
kernel/bpf/verifier.c
View File

@ -21011,7 +21011,10 @@ 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;
/* use env->insn_buf as two independent buffers */
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;
@ -21189,13 +21192,12 @@ 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;
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;
@ -21263,13 +21265,12 @@ 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;
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;
@ -21939,13 +21940,12 @@ 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;
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;
@ -21981,20 +21981,18 @@ 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) |
struct bpf_insn *patch = insn_buf;
if (isdiv)
*patch++ = 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),
};
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;
@ -22013,83 +22011,79 @@ 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;
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) |
*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),
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
0, 0, 1);
*patch++ = 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) |
0, 4, 1);
*patch++ = 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) |
0, 1, 0);
*patch++ = BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
BPF_MOV | BPF_K, insn->dst_reg,
0, 0, 0),
0, 0, 0);
/* BPF_NEG(LLONG_MIN) == -LLONG_MIN == LLONG_MIN */
BPF_RAW_INSN((is64 ? BPF_ALU64 : BPF_ALU) |
*patch++ = 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[] = {
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) |
*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),
BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
0, 0, 1);
*patch++ = 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) |
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),
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),
};
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;
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);
if (!is64) {
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
*patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
}
cnt = patch - insn_buf;
} 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;
if (!is64) {
*patch++ = BPF_JMP_IMM(BPF_JA, 0, 0, 1);
*patch++ = BPF_MOV32_REG(insn->dst_reg, insn->dst_reg);
}
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;