From patchwork Fri Jul 5 20:58:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduard Zingerman X-Patchwork-Id: 13725536 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D8A81144D21 for ; Fri, 5 Jul 2024 20:59:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213148; cv=none; b=VnbD9i0su3AUtj6OZuUg8tmsyCEPQi9jSnVjy39nQZneqZFKScEKWw3dB3pyK3D9vZ9lBVY3PKqObYi0jOBxaXQLi80Fe2DwdKNePmwgGuDua6RsfaDlYCe4ZP6HmGca/Itvd+N7821lQFMYCi0/9dEbLm7f0SlRENcZ9BJ6F5M= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213148; c=relaxed/simple; bh=P6uRfw9BCPxoxV2dw6YLfmdN8r3eKNpQ33XFA84dm0Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fKrGbMkLerhJYoWiZ0O6yC9tmApks+iXaqUTDYfsigq/Pp6rF/rO0ZVyvNlpSW6hjhS4WWJZd+VeC4yGSt/8j//xCo2GJdoxXNYoOHOw/ju1W+6EY1uRCuuiEqDPzkyAnhTDxV0taMTgoZBC4J9P+4Z7q1v7VpsutbTErUkEI9w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=MCVYd9he; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="MCVYd9he" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-1faad2f1967so22322945ad.0 for ; Fri, 05 Jul 2024 13:59:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1720213146; x=1720817946; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Fozi5LiTuziQTjTNkaVxe3WHHJIci5TysCjJHjXxvC8=; b=MCVYd9herXHVTPHbbmOtlBwlUZlfo+EppwUXtNQrY/FaQKER1ZECz/erWJIoh85/gf BZOqcvOBj5pHX6wwArYEAEIoAZWKJ0vhpomRnpNhC475q5rTFir1P9zNpAAp7//2Yc6A fPhXpUabdmVjtR6rj1eSGm4ojitz/7xGC9S3NsRpVouHXVleIkmeis9qrO400AZRpF1I OSYFDHphXegfXkg+3HAsT4dksBRmdmjP3U4sb0LqCLn4y14i0gF8avFmtPChDNZ7jfsl 2gY3CxTYmKyPXAPlP2iN8kWYktNBd5Fxhfzbg+uzYjXJAMjbiA0Dy0ChxbWXpdqR5Ct6 110w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720213146; x=1720817946; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Fozi5LiTuziQTjTNkaVxe3WHHJIci5TysCjJHjXxvC8=; b=RuqwZpJ9B4bzsvyhjydi4esOVmuBA/b0OVTKG+KStMQqCfBHUzKJ04VZN1HGWHIgNk H8z2lf2daPU4To/uGF1t+/oEVYCddeutXTHMvdoC0L41s8Mkxj+Y4+ok+V6lg4jLNHCC 5om/X+EisiV+W+myAH2cOPDCwNEMi5su2Izc/ycD8V2kJtiQ/EzTiCAHqAIwV2MSRzvq LNLS47sw8y8c/L26TMSXnlK/FQon5pRngLvfrBA4Dfevsr1MZeS0hFUTXvmXUNkiZiJi KH5B3y5bfq5ZqBX206x9z+xr+l0XA81yASCry5hrrqpW8yBYf3wYEXZwsdCQEF8Ledy9 sdxw== X-Gm-Message-State: AOJu0Yx9QSZffRPHfMH4HV9oNDTOXjHOaMhmtgJEB9H8JtykfjrdQSz9 va4dRnE9ljWUMhSzOsegeRRL34vSTF6haD1zomxDLF5ieTdAVq2prXeSVf5i X-Google-Smtp-Source: AGHT+IE+OP90d/yRNnWZKOHu28nzz1h/wq1Plfr8V63BJJ8kW5UV1smz3e7Gh3WxG70hmmV3nWTezw== X-Received: by 2002:a17:902:e745:b0:1f6:3580:65c9 with SMTP id d9443c01a7336-1fb370a0fc4mr74503605ad.26.1720213145694; Fri, 05 Jul 2024 13:59:05 -0700 (PDT) Received: from badger.. ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac11d8c52sm144767705ad.112.2024.07.05.13.59.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jul 2024 13:59:05 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, sunhao.th@gmail.com, Eduard Zingerman Subject: [PATCH bpf-next v2 1/3] bpf: track find_equal_scalars history on per-instruction level Date: Fri, 5 Jul 2024 13:58:48 -0700 Message-ID: <20240705205851.2635794-2-eddyz87@gmail.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240705205851.2635794-1-eddyz87@gmail.com> References: <20240705205851.2635794-1-eddyz87@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Use bpf_verifier_state->jmp_history to track which registers were updated by find_equal_scalars() when conditional jump was verified. Use recorded information in backtrack_insn() to propagate precision. E.g. for the following program: while verifying instructions r1 = r0 | if r1 < 8 goto ... | push r0,r1 as equal_scalars in jmp_history if r0 > 16 goto ... | push r0,r1 as equal_scalars in jmp_history r2 = r10 | r2 += r0 v mark_chain_precision(r0) while doing mark_chain_precision(r0) r1 = r0 ^ if r1 < 8 goto ... | mark r0,r1 as precise if r0 > 16 goto ... | mark r0,r1 as precise r2 = r10 | r2 += r0 | mark r0 precise Technically, achieve this as follows: - Use 10 bits to identify each register that gains range because of find_equal_scalars(): - 3 bits for frame number; - 6 bits for register or stack slot number; - 1 bit to indicate if register is spilled. - Use u64 as a vector of 6 such records + 4 bits for vector length. - Augment struct bpf_jmp_history_entry with field 'linked_regs' representing such vector. - When doing check_cond_jmp_op() remember up to 6 registers that gain range because of find_equal_scalars() in such a vector. - Don't propagate range information and reset IDs for registers that don't fit in 6-value vector. - Push a pair {instruction index, equal scalars vector} to bpf_verifier_state->jmp_history. - When doing backtrack_insn() check if any of recorded linked registers is currently marked precise, if so mark all linked registers as precise. This also requires fixes for two test_verifier tests: - precise: test 1 - precise: test 2 Both tests contain the following instruction sequence: 19: (bf) r2 = r9 ; R2=scalar(id=3) R9=scalar(id=3) 20: (a5) if r2 < 0x8 goto pc+1 ; R2=scalar(id=3,umin=8) 21: (95) exit 22: (07) r2 += 1 ; R2_w=scalar(id=3+1,...) 23: (bf) r1 = r10 ; R1_w=fp0 R10=fp0 24: (07) r1 += -8 ; R1_w=fp-8 25: (b7) r3 = 0 ; R3_w=0 26: (85) call bpf_probe_read_kernel#113 The call to bpf_probe_read_kernel() at (26) forces r2 to be precise. Previously, this forced all registers with same id to become precise immediately when mark_chain_precision() is called. After this change, the precision is propagated to registers sharing same id only when 'if' instruction is backtracked. Hence verification log for both tests is changed: regs=r2,r9 -> regs=r2 for instructions 25..20. Fixes: 904e6ddf4133 ("bpf: Use scalar ids in mark_chain_precision()") Reported-by: Hao Sun Closes: https://lore.kernel.org/bpf/CAEf4BzZ0xidVCqB47XnkXcNhkPWF6_nTV7yt+_Lf0kcFEut2Mg@mail.gmail.com/ Suggested-by: Andrii Nakryiko Signed-off-by: Eduard Zingerman --- include/linux/bpf_verifier.h | 4 + kernel/bpf/verifier.c | 231 ++++++++++++++++-- .../bpf/progs/verifier_subprog_precision.c | 2 +- .../testing/selftests/bpf/verifier/precise.c | 20 +- 4 files changed, 232 insertions(+), 25 deletions(-) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 2b54e25d2364..da450552c278 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -371,6 +371,10 @@ struct bpf_jmp_history_entry { u32 prev_idx : 22; /* special flags, e.g., whether insn is doing register stack spill/load */ u32 flags : 10; + /* additional registers that need precision tracking when this + * jump is backtracked, vector of six 10-bit records + */ + u64 linked_regs; }; /* Maximum number of register states that can exist at once */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e25ad5fb9115..ec493360607e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3335,9 +3335,87 @@ static bool is_jmp_point(struct bpf_verifier_env *env, int insn_idx) return env->insn_aux_data[insn_idx].jmp_point; } +#define ES_FRAMENO_BITS 3 +#define ES_SPI_BITS 6 +#define ES_ENTRY_BITS (ES_SPI_BITS + ES_FRAMENO_BITS + 1) +#define ES_SIZE_BITS 4 +#define ES_FRAMENO_MASK ((1ul << ES_FRAMENO_BITS) - 1) +#define ES_SPI_MASK ((1ul << ES_SPI_BITS) - 1) +#define ES_SIZE_MASK ((1ul << ES_SIZE_BITS) - 1) +#define ES_SPI_OFF ES_FRAMENO_BITS +#define ES_IS_REG_OFF (ES_SPI_BITS + ES_FRAMENO_BITS) +#define LINKED_REGS_MAX 6 + +struct reg_or_spill { + u8 frameno:3; + union { + u8 spi:6; + u8 regno:6; + }; + bool is_reg:1; +}; + +struct linked_regs { + int cnt; + struct reg_or_spill entries[LINKED_REGS_MAX]; +}; + +static struct reg_or_spill *linked_regs_push(struct linked_regs *s) +{ + if (s->cnt < LINKED_REGS_MAX) + return &s->entries[s->cnt++]; + + return NULL; +} + +/* Use u64 as a vector of 6 10-bit values, use first 4-bits to track + * number of elements currently in stack. + * Pack one history entry for equal scalars as 10 bits in the following format: + * - 3-bits frameno + * - 6-bits spi_or_reg + * - 1-bit is_reg + */ +static u64 linked_regs_pack(struct linked_regs *s) +{ + u64 val = 0; + int i; + + for (i = 0; i < s->cnt; ++i) { + struct reg_or_spill *e = &s->entries[i]; + u64 tmp = 0; + + tmp |= e->frameno; + tmp |= e->spi << ES_SPI_OFF; + tmp |= (e->is_reg ? 1 : 0) << ES_IS_REG_OFF; + + val <<= ES_ENTRY_BITS; + val |= tmp; + } + val <<= ES_SIZE_BITS; + val |= s->cnt; + return val; +} + +static void linked_regs_unpack(u64 val, struct linked_regs *s) +{ + int i; + + s->cnt = val & ES_SIZE_MASK; + val >>= ES_SIZE_BITS; + + for (i = 0; i < s->cnt; ++i) { + struct reg_or_spill *e = &s->entries[i]; + + e->frameno = val & ES_FRAMENO_MASK; + e->spi = (val >> ES_SPI_OFF) & ES_SPI_MASK; + e->is_reg = (val >> ES_IS_REG_OFF) & 0x1; + val >>= ES_ENTRY_BITS; + } +} + /* for any branch, call, exit record the history of jmps in the given state */ static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_state *cur, - int insn_flags) + int insn_flags, u64 linked_regs) { u32 cnt = cur->jmp_history_cnt; struct bpf_jmp_history_entry *p; @@ -3353,6 +3431,10 @@ static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_st "verifier insn history bug: insn_idx %d cur flags %x new flags %x\n", env->insn_idx, env->cur_hist_ent->flags, insn_flags); env->cur_hist_ent->flags |= insn_flags; + WARN_ONCE(env->cur_hist_ent->linked_regs != 0, + "verifier insn history bug: insn_idx %d linked_regs != 0: %#llx\n", + env->insn_idx, env->cur_hist_ent->linked_regs); + env->cur_hist_ent->linked_regs = linked_regs; return 0; } @@ -3367,6 +3449,7 @@ static int push_jmp_history(struct bpf_verifier_env *env, struct bpf_verifier_st p->idx = env->insn_idx; p->prev_idx = env->prev_insn_idx; p->flags = insn_flags; + p->linked_regs = linked_regs; cur->jmp_history_cnt = cnt; env->cur_hist_ent = p; @@ -3532,6 +3615,11 @@ static inline bool bt_is_reg_set(struct backtrack_state *bt, u32 reg) return bt->reg_masks[bt->frame] & (1 << reg); } +static inline bool bt_is_frame_reg_set(struct backtrack_state *bt, u32 frame, u32 reg) +{ + return bt->reg_masks[frame] & (1 << reg); +} + static inline bool bt_is_frame_slot_set(struct backtrack_state *bt, u32 frame, u32 slot) { return bt->stack_masks[frame] & (1ull << slot); @@ -3576,6 +3664,42 @@ static void fmt_stack_mask(char *buf, ssize_t buf_sz, u64 stack_mask) } } +/* If any register R in hist->linked_regs is marked as precise in bt, + * do bt_set_frame_{reg,slot}(bt, R) for all registers in hist->linked_regs. + */ +static void bt_sync_linked_regs(struct backtrack_state *bt, struct bpf_jmp_history_entry *hist) +{ + struct linked_regs linked_regs; + bool some_precise = false; + int i; + + if (!hist || hist->linked_regs == 0) + return; + + linked_regs_unpack(hist->linked_regs, &linked_regs); + for (i = 0; i < linked_regs.cnt; ++i) { + struct reg_or_spill *e = &linked_regs.entries[i]; + + if ((e->is_reg && bt_is_frame_reg_set(bt, e->frameno, e->regno)) || + (!e->is_reg && bt_is_frame_slot_set(bt, e->frameno, e->spi))) { + some_precise = true; + break; + } + } + + if (!some_precise) + return; + + for (i = 0; i < linked_regs.cnt; ++i) { + struct reg_or_spill *e = &linked_regs.entries[i]; + + if (e->is_reg) + bt_set_frame_reg(bt, e->frameno, e->regno); + else + bt_set_frame_slot(bt, e->frameno, e->spi); + } +} + static bool calls_callback(struct bpf_verifier_env *env, int insn_idx); /* For given verifier state backtrack_insn() is called from the last insn to @@ -3615,6 +3739,12 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx, print_bpf_insn(&cbs, insn, env->allow_ptr_leaks); } + /* If there is a history record that some registers gained range at this insn, + * propagate precision marks to those registers, so that bt_is_reg_set() + * accounts for these registers. + */ + bt_sync_linked_regs(bt, hist); + if (class == BPF_ALU || class == BPF_ALU64) { if (!bt_is_reg_set(bt, dreg)) return 0; @@ -3844,6 +3974,7 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx, */ bt_set_reg(bt, dreg); bt_set_reg(bt, sreg); + } else if (BPF_SRC(insn->code) == BPF_K) { /* else dreg K * Only dreg still needs precision before * this insn, so for the K-based conditional @@ -3862,6 +3993,10 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx, /* to be analyzed */ return -ENOTSUPP; } + /* Propagate precision marks to linked registers, to account for + * registers marked as precise in this function. + */ + bt_sync_linked_regs(bt, hist); return 0; } @@ -4624,7 +4759,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, } if (insn_flags) - return push_jmp_history(env, env->cur_state, insn_flags); + return push_jmp_history(env, env->cur_state, insn_flags, 0); return 0; } @@ -4929,7 +5064,7 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env, insn_flags = 0; /* we are not restoring spilled register */ } if (insn_flags) - return push_jmp_history(env, env->cur_state, insn_flags); + return push_jmp_history(env, env->cur_state, insn_flags, 0); return 0; } @@ -15154,14 +15289,66 @@ static bool try_match_pkt_pointers(const struct bpf_insn *insn, return true; } -static void find_equal_scalars(struct bpf_verifier_state *vstate, - struct bpf_reg_state *known_reg) +static void __find_equal_scalars(struct linked_regs *reg_set, struct bpf_reg_state *reg, + u32 id, u32 frameno, u32 spi_or_reg, bool is_reg) +{ + struct reg_or_spill *e; + + if (reg->type != SCALAR_VALUE || (reg->id & ~BPF_ADD_CONST) != id) + return; + + e = linked_regs_push(reg_set); + if (e) { + e->frameno = frameno; + e->is_reg = is_reg; + e->regno = spi_or_reg; + } else { + reg->id = 0; + } +} + +/* For all R being scalar registers or spilled scalar registers + * in verifier state, save R in linked_regs if R->id == id. + * If there are too many Rs sharing same id, reset id for leftover Rs. + */ +static void find_equal_scalars(struct bpf_verifier_state *vstate, u32 id, + struct linked_regs *linked_regs) +{ + struct bpf_func_state *func; + struct bpf_reg_state *reg; + int i, j; + + id = id & ~BPF_ADD_CONST; + for (i = vstate->curframe; i >= 0; i--) { + func = vstate->frame[i]; + for (j = 0; j < BPF_REG_FP; j++) { + reg = &func->regs[j]; + __find_equal_scalars(linked_regs, reg, id, i, j, true); + } + for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) { + if (!is_spilled_reg(&func->stack[j])) + continue; + reg = &func->stack[j].spilled_ptr; + __find_equal_scalars(linked_regs, reg, id, i, j, false); + } + } +} + +/* For all R in linked_regs, copy known_reg range into R + * if R->id == known_reg->id. + */ +static void copy_known_reg(struct bpf_verifier_state *vstate, struct bpf_reg_state *known_reg, + struct linked_regs *linked_regs) { struct bpf_reg_state fake_reg; - struct bpf_func_state *state; struct bpf_reg_state *reg; + struct reg_or_spill *e; + int i; - bpf_for_each_reg_in_vstate(vstate, state, reg, ({ + for (i = 0; i < linked_regs->cnt; ++i) { + e = &linked_regs->entries[i]; + reg = e->is_reg ? &vstate->frame[e->frameno]->regs[e->regno] + : &vstate->frame[e->frameno]->stack[e->spi].spilled_ptr; if (reg->type != SCALAR_VALUE || reg == known_reg) continue; if ((reg->id & ~BPF_ADD_CONST) != (known_reg->id & ~BPF_ADD_CONST)) @@ -15187,7 +15374,7 @@ static void find_equal_scalars(struct bpf_verifier_state *vstate, scalar_min_max_add(reg, &fake_reg); reg->var_off = tnum_add(reg->var_off, fake_reg.var_off); } - })); + } } static int check_cond_jmp_op(struct bpf_verifier_env *env, @@ -15198,6 +15385,7 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs; struct bpf_reg_state *dst_reg, *other_branch_regs, *src_reg = NULL; struct bpf_reg_state *eq_branch_regs; + struct linked_regs linked_regs = {}; struct bpf_reg_state fake_reg = {}; u8 opcode = BPF_OP(insn->code); bool is_jmp32; @@ -15312,6 +15500,21 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, return 0; } + /* Push scalar registers sharing same ID to jump history, + * do this before creating 'other_branch', so that both + * 'this_branch' and 'other_branch' share this history + * if parent state is created. + */ + if (BPF_SRC(insn->code) == BPF_X && src_reg->type == SCALAR_VALUE && src_reg->id) + find_equal_scalars(this_branch, src_reg->id, &linked_regs); + if (dst_reg->type == SCALAR_VALUE && dst_reg->id) + find_equal_scalars(this_branch, dst_reg->id, &linked_regs); + if (linked_regs.cnt > 1) { + err = push_jmp_history(env, this_branch, 0, linked_regs_pack(&linked_regs)); + if (err) + return err; + } + other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx, false); if (!other_branch) @@ -15336,13 +15539,13 @@ static int check_cond_jmp_op(struct bpf_verifier_env *env, if (BPF_SRC(insn->code) == BPF_X && src_reg->type == SCALAR_VALUE && src_reg->id && !WARN_ON_ONCE(src_reg->id != other_branch_regs[insn->src_reg].id)) { - find_equal_scalars(this_branch, src_reg); - find_equal_scalars(other_branch, &other_branch_regs[insn->src_reg]); + copy_known_reg(this_branch, src_reg, &linked_regs); + copy_known_reg(other_branch, &other_branch_regs[insn->src_reg], &linked_regs); } if (dst_reg->type == SCALAR_VALUE && dst_reg->id && !WARN_ON_ONCE(dst_reg->id != other_branch_regs[insn->dst_reg].id)) { - find_equal_scalars(this_branch, dst_reg); - find_equal_scalars(other_branch, &other_branch_regs[insn->dst_reg]); + copy_known_reg(this_branch, dst_reg, &linked_regs); + copy_known_reg(other_branch, &other_branch_regs[insn->dst_reg], &linked_regs); } /* if one pointer register is compared to another pointer @@ -17624,7 +17827,7 @@ static int is_state_visited(struct bpf_verifier_env *env, int insn_idx) * the current state. */ if (is_jmp_point(env, env->insn_idx)) - err = err ? : push_jmp_history(env, cur, 0); + err = err ? : push_jmp_history(env, cur, 0, 0); err = err ? : propagate_precision(env, &sl->state); if (err) return err; @@ -17892,7 +18095,7 @@ static int do_check(struct bpf_verifier_env *env) } if (is_jmp_point(env, env->insn_idx)) { - err = push_jmp_history(env, state, 0); + err = push_jmp_history(env, state, 0, 0); if (err) return err; } diff --git a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c index 6a6fad625f7e..9d415f7ce599 100644 --- a/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c +++ b/tools/testing/selftests/bpf/progs/verifier_subprog_precision.c @@ -278,7 +278,7 @@ __msg("mark_precise: frame0: last_idx 14 first_idx 9") __msg("mark_precise: frame0: regs=r6 stack= before 13: (bf) r1 = r7") __msg("mark_precise: frame0: regs=r6 stack= before 12: (27) r6 *= 4") __msg("mark_precise: frame0: regs=r6 stack= before 11: (25) if r6 > 0x3 goto pc+4") -__msg("mark_precise: frame0: regs=r6 stack= before 10: (bf) r6 = r0") +__msg("mark_precise: frame0: regs=r0,r6 stack= before 10: (bf) r6 = r0") __msg("mark_precise: frame0: regs=r0 stack= before 9: (85) call bpf_loop") /* State entering callback body popped from states stack */ __msg("from 9 to 17: frame1:") diff --git a/tools/testing/selftests/bpf/verifier/precise.c b/tools/testing/selftests/bpf/verifier/precise.c index 90643ccc221d..64d722199e8f 100644 --- a/tools/testing/selftests/bpf/verifier/precise.c +++ b/tools/testing/selftests/bpf/verifier/precise.c @@ -39,11 +39,11 @@ .result = VERBOSE_ACCEPT, .errstr = "mark_precise: frame0: last_idx 26 first_idx 20\ - mark_precise: frame0: regs=r2,r9 stack= before 25\ - mark_precise: frame0: regs=r2,r9 stack= before 24\ - mark_precise: frame0: regs=r2,r9 stack= before 23\ - mark_precise: frame0: regs=r2,r9 stack= before 22\ - mark_precise: frame0: regs=r2,r9 stack= before 20\ + mark_precise: frame0: regs=r2 stack= before 25\ + mark_precise: frame0: regs=r2 stack= before 24\ + mark_precise: frame0: regs=r2 stack= before 23\ + mark_precise: frame0: regs=r2 stack= before 22\ + mark_precise: frame0: regs=r2 stack= before 20\ mark_precise: frame0: parent state regs=r2,r9 stack=:\ mark_precise: frame0: last_idx 19 first_idx 10\ mark_precise: frame0: regs=r2,r9 stack= before 19\ @@ -100,11 +100,11 @@ .errstr = "26: (85) call bpf_probe_read_kernel#113\ mark_precise: frame0: last_idx 26 first_idx 22\ - mark_precise: frame0: regs=r2,r9 stack= before 25\ - mark_precise: frame0: regs=r2,r9 stack= before 24\ - mark_precise: frame0: regs=r2,r9 stack= before 23\ - mark_precise: frame0: regs=r2,r9 stack= before 22\ - mark_precise: frame0: parent state regs=r2,r9 stack=:\ + mark_precise: frame0: regs=r2 stack= before 25\ + mark_precise: frame0: regs=r2 stack= before 24\ + mark_precise: frame0: regs=r2 stack= before 23\ + mark_precise: frame0: regs=r2 stack= before 22\ + mark_precise: frame0: parent state regs=r2 stack=:\ mark_precise: frame0: last_idx 20 first_idx 20\ mark_precise: frame0: regs=r2,r9 stack= before 20\ mark_precise: frame0: parent state regs=r2,r9 stack=:\ From patchwork Fri Jul 5 20:58:49 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduard Zingerman X-Patchwork-Id: 13725537 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pl1-f172.google.com (mail-pl1-f172.google.com [209.85.214.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17CE214431C for ; Fri, 5 Jul 2024 20:59:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213150; cv=none; b=F7IOocsQz5tLTzhR7l4k+tncfX9T3iWyaRp2uyPfb8UgJkqtPt2OEcylf41830KM6w+++p3vx37M2Nv7P+S7cSSpOZ9DfLtoPu225fkaiFK7XUQwcRhtRrF1GFXuX9KIWTs3AFBE8v9y/pQesyLM0rR2amDjbEtGgzHFmdQ4Kmc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213150; c=relaxed/simple; bh=eVb2LuYnI0XaKpC6B0T14EQtXDp5+Mh4oodmSQMqZyE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kFdpvtbKiob6CwmCCyy+TsIuK5oW1hROidbM6B5NQMOe8bLtA2kmOZlH8fHlSLepWCVhlASwxjaOslf69c0EBgnszXtTGJw5+rPhKLM6mYNsM5vDLdB9bIN4Nxch44HMPuD0LibFrtS/1tIHozLprQZ7a+VIXzIM8xdY0Cwtw/0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=iEzcV6k5; arc=none smtp.client-ip=209.85.214.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iEzcV6k5" Received: by mail-pl1-f172.google.com with SMTP id d9443c01a7336-1fb05ac6b77so13193045ad.0 for ; Fri, 05 Jul 2024 13:59:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1720213147; x=1720817947; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=1k/22QUlE0RnNOKRpI+oEBlx7GvAdG+tnP+k4BYS9qw=; b=iEzcV6k58/iRB+zzhymNHEHt2Lt/TiWE35l6BtZVbgy6SxgtOasR88jZVGwWGRP2BN WAFBhha/eosm/togGfFu3FuvhAjtqC7qv7X5QDdavDVRzT8TKcOSyoNBO7Z5Xsl5w8KC ryk9SqcefNLOpt2OtvoP9XVm0wEqrzDxadVYrkclOdFx+5YAze+ixL7/Z9vFpIs0ScS5 W9ugBS2ATAZ8wi7r75l9LJ2CNiDxGV1/XW3cY1FUZrq8EiGcLn3PSPrhPULvT1y4+3nj vBEH3l10m/btULlxlThDHtBSe5rQhr1l2jXHU6PhEg98F9hbLOXQNGSNSGWUiDgXWC7u z2BA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720213147; x=1720817947; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=1k/22QUlE0RnNOKRpI+oEBlx7GvAdG+tnP+k4BYS9qw=; b=xOsCLlEOoiD5W1bY8GKrkk+BnQrbzELCc/bTv5Y4smmsizdhvX3uJflv4e/W7JbP1n gfql9iDwKnJjitm+tZiiUOnSHy6BpQO6sDJsnDULufmhwOdzM1JWsFBe35kh9jojotwi RGZ5xtJgMusy3A4b0S2ygV8W7SaU2mVLgPtlgkYq7d8tOFg1KV92TcjzY8J1dgFo77wP gwVOnVEz+kYG4XDWfW8yPVntR1Pvg7MhYnLUJ9vbULNxUy/otfoiZe8Dg4nM9cl9hrUV PFg55HqhOjEgrv92fDWA7m4pDKpT/kQEIPL7r6Np+7HfjphB9xateXJSl4UIKgoAOU+c kZ7Q== X-Gm-Message-State: AOJu0YyUiagQSWvDkY4iyeE3rlEOG/V7i0eN/q5srKVWLUop4puSxxeZ QF+axp0q37j1nmDrBKq7GHq4GLrSKbcX+zgB7NZ2akbqBKmW4X9Qn9aDKXqI X-Google-Smtp-Source: AGHT+IExu+97EXH107P4x4+ymIlYic0dPTxBRb14JyCLBWUJrJ69NHLKRrLiSuUJ8jzOu4zVe0WZug== X-Received: by 2002:a17:902:d48d:b0:1f9:df83:8ab2 with SMTP id d9443c01a7336-1fb33f2de74mr46475045ad.58.1720213146871; Fri, 05 Jul 2024 13:59:06 -0700 (PDT) Received: from badger.. ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac11d8c52sm144767705ad.112.2024.07.05.13.59.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jul 2024 13:59:06 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, sunhao.th@gmail.com, Eduard Zingerman Subject: [PATCH bpf-next v2 2/3] bpf: remove mark_precise_scalar_ids() Date: Fri, 5 Jul 2024 13:58:49 -0700 Message-ID: <20240705205851.2635794-3-eddyz87@gmail.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240705205851.2635794-1-eddyz87@gmail.com> References: <20240705205851.2635794-1-eddyz87@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Function mark_precise_scalar_ids() is superseded by bt_sync_linked_regs() and equal scalars tracking in jump history. mark_precise_scalar_ids() propagates precision over registers sharing same ID on parent/child state boundaries, while jump history records allow bt_sync_linked_regs() to propagate same information with instruction level granularity, which is strictly more precise. This commit removes mark_precise_scalar_ids() and updates test cases in progs/verifier_scalar_ids to reflect new verifier behavior. The tests are updated in the following manner: - mark_precise_scalar_ids() propagated precision regardless of presence of conditional jumps, while new jump history based logic only kicks in when conditional jumps are present. Hence test cases are augmented with conditional jumps to still trigger precision propagation. - As equal scalars tracking no longer relies on parent/child state boundaries some test cases are no longer interesting, such test cases are removed, namely: - precision_same_state and precision_cross_state are superseded by equal_scalars_bpf_k; - precision_same_state_broken_link and equal_scalars_broken_link are superseded by equal_scalars_broken_link. Signed-off-by: Eduard Zingerman --- kernel/bpf/verifier.c | 115 ------------ .../selftests/bpf/progs/verifier_scalar_ids.c | 171 ++++++------------ .../testing/selftests/bpf/verifier/precise.c | 8 +- 3 files changed, 59 insertions(+), 235 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ec493360607e..0c25eecf05f8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4124,96 +4124,6 @@ static void mark_all_scalars_imprecise(struct bpf_verifier_env *env, struct bpf_ } } -static bool idset_contains(struct bpf_idset *s, u32 id) -{ - u32 i; - - for (i = 0; i < s->count; ++i) - if (s->ids[i] == (id & ~BPF_ADD_CONST)) - return true; - - return false; -} - -static int idset_push(struct bpf_idset *s, u32 id) -{ - if (WARN_ON_ONCE(s->count >= ARRAY_SIZE(s->ids))) - return -EFAULT; - s->ids[s->count++] = id & ~BPF_ADD_CONST; - return 0; -} - -static void idset_reset(struct bpf_idset *s) -{ - s->count = 0; -} - -/* Collect a set of IDs for all registers currently marked as precise in env->bt. - * Mark all registers with these IDs as precise. - */ -static int mark_precise_scalar_ids(struct bpf_verifier_env *env, struct bpf_verifier_state *st) -{ - struct bpf_idset *precise_ids = &env->idset_scratch; - struct backtrack_state *bt = &env->bt; - struct bpf_func_state *func; - struct bpf_reg_state *reg; - DECLARE_BITMAP(mask, 64); - int i, fr; - - idset_reset(precise_ids); - - for (fr = bt->frame; fr >= 0; fr--) { - func = st->frame[fr]; - - bitmap_from_u64(mask, bt_frame_reg_mask(bt, fr)); - for_each_set_bit(i, mask, 32) { - reg = &func->regs[i]; - if (!reg->id || reg->type != SCALAR_VALUE) - continue; - if (idset_push(precise_ids, reg->id)) - return -EFAULT; - } - - bitmap_from_u64(mask, bt_frame_stack_mask(bt, fr)); - for_each_set_bit(i, mask, 64) { - if (i >= func->allocated_stack / BPF_REG_SIZE) - break; - if (!is_spilled_scalar_reg(&func->stack[i])) - continue; - reg = &func->stack[i].spilled_ptr; - if (!reg->id) - continue; - if (idset_push(precise_ids, reg->id)) - return -EFAULT; - } - } - - for (fr = 0; fr <= st->curframe; ++fr) { - func = st->frame[fr]; - - for (i = BPF_REG_0; i < BPF_REG_10; ++i) { - reg = &func->regs[i]; - if (!reg->id) - continue; - if (!idset_contains(precise_ids, reg->id)) - continue; - bt_set_frame_reg(bt, fr, i); - } - for (i = 0; i < func->allocated_stack / BPF_REG_SIZE; ++i) { - if (!is_spilled_scalar_reg(&func->stack[i])) - continue; - reg = &func->stack[i].spilled_ptr; - if (!reg->id) - continue; - if (!idset_contains(precise_ids, reg->id)) - continue; - bt_set_frame_slot(bt, fr, i); - } - } - - return 0; -} - /* * __mark_chain_precision() backtracks BPF program instruction sequence and * chain of verifier states making sure that register *regno* (if regno >= 0) @@ -4346,31 +4256,6 @@ static int __mark_chain_precision(struct bpf_verifier_env *env, int regno) bt->frame, last_idx, first_idx, subseq_idx); } - /* If some register with scalar ID is marked as precise, - * make sure that all registers sharing this ID are also precise. - * This is needed to estimate effect of find_equal_scalars(). - * Do this at the last instruction of each state, - * bpf_reg_state::id fields are valid for these instructions. - * - * Allows to track precision in situation like below: - * - * r2 = unknown value - * ... - * --- state #0 --- - * ... - * r1 = r2 // r1 and r2 now share the same ID - * ... - * --- state #1 {r1.id = A, r2.id = A} --- - * ... - * if (r2 > 10) goto exit; // find_equal_scalars() assigns range to r1 - * ... - * --- state #2 {r1.id = A, r2.id = A} --- - * r3 = r10 - * r3 += r1 // need to mark both r1 and r2 - */ - if (mark_precise_scalar_ids(env, st)) - return -EFAULT; - if (last_idx < 0) { /* we are at the entry into subprog, which * is expected for global funcs, but only if diff --git a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c index 13b29a7faa71..639db72b1c55 100644 --- a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c +++ b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c @@ -5,54 +5,27 @@ #include "bpf_misc.h" /* Check that precision marks propagate through scalar IDs. - * Registers r{0,1,2} have the same scalar ID at the moment when r0 is - * marked to be precise, this mark is immediately propagated to r{1,2}. + * Registers r{0,1,2} have the same scalar ID. + * Range information is propagated for scalars sharing same ID. + * Check that precision mark for r0 causes precision marks for r{1,2} + * when range information is propagated for 'if ' insn. */ SEC("socket") __success __log_level(2) -__msg("frame0: regs=r0,r1,r2 stack= before 4: (bf) r3 = r10") -__msg("frame0: regs=r0,r1,r2 stack= before 3: (bf) r2 = r0") -__msg("frame0: regs=r0,r1 stack= before 2: (bf) r1 = r0") -__msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") -__msg("frame0: regs=r0 stack= before 0: (85) call bpf_ktime_get_ns") -__flag(BPF_F_TEST_STATE_FREQ) -__naked void precision_same_state(void) -{ - asm volatile ( - /* r0 = random number up to 0xff */ - "call %[bpf_ktime_get_ns];" - "r0 &= 0xff;" - /* tie r0.id == r1.id == r2.id */ - "r1 = r0;" - "r2 = r0;" - /* force r0 to be precise, this immediately marks r1 and r2 as - * precise as well because of shared IDs - */ - "r3 = r10;" - "r3 += r0;" - "r0 = 0;" - "exit;" - : - : __imm(bpf_ktime_get_ns) - : __clobber_all); -} - -/* Same as precision_same_state, but mark propagates through state / - * parent state boundary. - */ -SEC("socket") -__success __log_level(2) -__msg("frame0: last_idx 6 first_idx 5 subseq_idx -1") -__msg("frame0: regs=r0,r1,r2 stack= before 5: (bf) r3 = r10") +/* first 'if' branch */ +__msg("6: (0f) r3 += r0") +__msg("frame0: regs=r0 stack= before 4: (25) if r1 > 0x7 goto pc+0") __msg("frame0: parent state regs=r0,r1,r2 stack=:") -__msg("frame0: regs=r0,r1,r2 stack= before 4: (05) goto pc+0") __msg("frame0: regs=r0,r1,r2 stack= before 3: (bf) r2 = r0") -__msg("frame0: regs=r0,r1 stack= before 2: (bf) r1 = r0") -__msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") -__msg("frame0: parent state regs=r0 stack=:") -__msg("frame0: regs=r0 stack= before 0: (85) call bpf_ktime_get_ns") +/* second 'if' branch */ +__msg("from 4 to 5: ") +__msg("6: (0f) r3 += r0") +__msg("frame0: regs=r0 stack= before 5: (bf) r3 = r10") +__msg("frame0: regs=r0 stack= before 4: (25) if r1 > 0x7 goto pc+0") +/* parent state already has r{0,1,2} as precise */ +__msg("frame0: parent state regs= stack=:") __flag(BPF_F_TEST_STATE_FREQ) -__naked void precision_cross_state(void) +__naked void equal_scalars_bpf_k(void) { asm volatile ( /* r0 = random number up to 0xff */ @@ -61,9 +34,8 @@ __naked void precision_cross_state(void) /* tie r0.id == r1.id == r2.id */ "r1 = r0;" "r2 = r0;" - /* force checkpoint */ - "goto +0;" - /* force r0 to be precise, this immediately marks r1 and r2 as + "if r1 > 7 goto +0;" + /* force r0 to be precise, this eventually marks r1 and r2 as * precise as well because of shared IDs */ "r3 = r10;" @@ -75,59 +47,18 @@ __naked void precision_cross_state(void) : __clobber_all); } -/* Same as precision_same_state, but break one of the +/* Same as equal_scalars_bpf_k, but break one of the * links, note that r1 is absent from regs=... in __msg below. */ SEC("socket") __success __log_level(2) -__msg("frame0: regs=r0,r2 stack= before 5: (bf) r3 = r10") -__msg("frame0: regs=r0,r2 stack= before 4: (b7) r1 = 0") -__msg("frame0: regs=r0,r2 stack= before 3: (bf) r2 = r0") -__msg("frame0: regs=r0 stack= before 2: (bf) r1 = r0") -__msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") -__msg("frame0: regs=r0 stack= before 0: (85) call bpf_ktime_get_ns") -__flag(BPF_F_TEST_STATE_FREQ) -__naked void precision_same_state_broken_link(void) -{ - asm volatile ( - /* r0 = random number up to 0xff */ - "call %[bpf_ktime_get_ns];" - "r0 &= 0xff;" - /* tie r0.id == r1.id == r2.id */ - "r1 = r0;" - "r2 = r0;" - /* break link for r1, this is the only line that differs - * compared to the previous test - */ - "r1 = 0;" - /* force r0 to be precise, this immediately marks r1 and r2 as - * precise as well because of shared IDs - */ - "r3 = r10;" - "r3 += r0;" - "r0 = 0;" - "exit;" - : - : __imm(bpf_ktime_get_ns) - : __clobber_all); -} - -/* Same as precision_same_state_broken_link, but with state / - * parent state boundary. - */ -SEC("socket") -__success __log_level(2) -__msg("frame0: regs=r0,r2 stack= before 6: (bf) r3 = r10") -__msg("frame0: regs=r0,r2 stack= before 5: (b7) r1 = 0") -__msg("frame0: parent state regs=r0,r2 stack=:") -__msg("frame0: regs=r0,r1,r2 stack= before 4: (05) goto pc+0") -__msg("frame0: regs=r0,r1,r2 stack= before 3: (bf) r2 = r0") -__msg("frame0: regs=r0,r1 stack= before 2: (bf) r1 = r0") -__msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") +__msg("7: (0f) r3 += r0") +__msg("frame0: regs=r0 stack= before 6: (bf) r3 = r10") __msg("frame0: parent state regs=r0 stack=:") -__msg("frame0: regs=r0 stack= before 0: (85) call bpf_ktime_get_ns") +__msg("frame0: regs=r0 stack= before 5: (25) if r0 > 0x7 goto pc+0") +__msg("frame0: parent state regs=r0,r2 stack=:") __flag(BPF_F_TEST_STATE_FREQ) -__naked void precision_cross_state_broken_link(void) +__naked void equal_scalars_broken_link(void) { asm volatile ( /* r0 = random number up to 0xff */ @@ -136,18 +67,13 @@ __naked void precision_cross_state_broken_link(void) /* tie r0.id == r1.id == r2.id */ "r1 = r0;" "r2 = r0;" - /* force checkpoint, although link between r1 and r{0,2} is - * broken by the next statement current precision tracking - * algorithm can't react to it and propagates mark for r1 to - * the parent state. - */ - "goto +0;" /* break link for r1, this is the only line that differs - * compared to precision_cross_state() + * compared to the previous test */ "r1 = 0;" - /* force r0 to be precise, this immediately marks r1 and r2 as - * precise as well because of shared IDs + "if r0 > 7 goto +0;" + /* force r0 to be precise, + * this eventually marks r2 as precise because of shared IDs */ "r3 = r10;" "r3 += r0;" @@ -164,10 +90,16 @@ __naked void precision_cross_state_broken_link(void) */ SEC("socket") __success __log_level(2) -__msg("11: (0f) r2 += r1") +__msg("12: (0f) r2 += r1") /* Current state */ -__msg("frame2: last_idx 11 first_idx 10 subseq_idx -1") -__msg("frame2: regs=r1 stack= before 10: (bf) r2 = r10") +__msg("frame2: last_idx 12 first_idx 11 subseq_idx -1 ") +__msg("frame2: regs=r1 stack= before 11: (bf) r2 = r10") +__msg("frame2: parent state regs=r1 stack=") +__msg("frame1: parent state regs= stack=") +__msg("frame0: parent state regs= stack=") +/* Parent state */ +__msg("frame2: last_idx 10 first_idx 10 subseq_idx 11 ") +__msg("frame2: regs=r1 stack= before 10: (25) if r1 > 0x7 goto pc+0") __msg("frame2: parent state regs=r1 stack=") /* frame1.r{6,7} are marked because mark_precise_scalar_ids() * looks for all registers with frame2.r1.id in the current state @@ -192,7 +124,7 @@ __msg("frame1: regs=r1 stack= before 4: (85) call pc+1") __msg("frame0: parent state regs=r1,r6 stack=") /* Parent state */ __msg("frame0: last_idx 3 first_idx 1 subseq_idx 4") -__msg("frame0: regs=r0,r1,r6 stack= before 3: (bf) r6 = r0") +__msg("frame0: regs=r1,r6 stack= before 3: (bf) r6 = r0") __msg("frame0: regs=r0,r1 stack= before 2: (bf) r1 = r0") __msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") __flag(BPF_F_TEST_STATE_FREQ) @@ -230,7 +162,8 @@ static __naked __noinline __used void precision_many_frames__bar(void) { asm volatile ( - /* force r1 to be precise, this immediately marks: + "if r1 > 7 goto +0;" + /* force r1 to be precise, this eventually marks: * - bar frame r1 * - foo frame r{1,6,7} * - main frame r{1,6} @@ -247,14 +180,16 @@ void precision_many_frames__bar(void) */ SEC("socket") __success __log_level(2) +__msg("11: (0f) r2 += r1") /* foo frame */ -__msg("frame1: regs=r1 stack=-8,-16 before 9: (bf) r2 = r10") +__msg("frame1: regs=r1 stack= before 10: (bf) r2 = r10") +__msg("frame1: regs=r1 stack= before 9: (25) if r1 > 0x7 goto pc+0") __msg("frame1: regs=r1 stack=-8,-16 before 8: (7b) *(u64 *)(r10 -16) = r1") __msg("frame1: regs=r1 stack=-8 before 7: (7b) *(u64 *)(r10 -8) = r1") __msg("frame1: regs=r1 stack= before 4: (85) call pc+2") /* main frame */ -__msg("frame0: regs=r0,r1 stack=-8 before 3: (7b) *(u64 *)(r10 -8) = r1") -__msg("frame0: regs=r0,r1 stack= before 2: (bf) r1 = r0") +__msg("frame0: regs=r1 stack=-8 before 3: (7b) *(u64 *)(r10 -8) = r1") +__msg("frame0: regs=r1 stack= before 2: (bf) r1 = r0") __msg("frame0: regs=r0 stack= before 1: (57) r0 &= 255") __flag(BPF_F_TEST_STATE_FREQ) __naked void precision_stack(void) @@ -283,7 +218,8 @@ void precision_stack__foo(void) */ "*(u64*)(r10 - 8) = r1;" "*(u64*)(r10 - 16) = r1;" - /* force r1 to be precise, this immediately marks: + "if r1 > 7 goto +0;" + /* force r1 to be precise, this eventually marks: * - foo frame r1,fp{-8,-16} * - main frame r1,fp{-8} */ @@ -299,15 +235,17 @@ void precision_stack__foo(void) SEC("socket") __success __log_level(2) /* r{6,7} */ -__msg("11: (0f) r3 += r7") -__msg("frame0: regs=r6,r7 stack= before 10: (bf) r3 = r10") +__msg("12: (0f) r3 += r7") +__msg("frame0: regs=r7 stack= before 11: (bf) r3 = r10") +__msg("frame0: regs=r7 stack= before 9: (25) if r7 > 0x7 goto pc+0") /* ... skip some insns ... */ __msg("frame0: regs=r6,r7 stack= before 3: (bf) r7 = r0") __msg("frame0: regs=r0,r6 stack= before 2: (bf) r6 = r0") /* r{8,9} */ -__msg("12: (0f) r3 += r9") -__msg("frame0: regs=r8,r9 stack= before 11: (0f) r3 += r7") +__msg("13: (0f) r3 += r9") +__msg("frame0: regs=r9 stack= before 12: (0f) r3 += r7") /* ... skip some insns ... */ +__msg("frame0: regs=r9 stack= before 10: (25) if r9 > 0x7 goto pc+0") __msg("frame0: regs=r8,r9 stack= before 7: (bf) r9 = r0") __msg("frame0: regs=r0,r8 stack= before 6: (bf) r8 = r0") __flag(BPF_F_TEST_STATE_FREQ) @@ -328,8 +266,9 @@ __naked void precision_two_ids(void) "r9 = r0;" /* clear r0 id */ "r0 = 0;" - /* force checkpoint */ - "goto +0;" + /* propagate equal scalars precision */ + "if r7 > 7 goto +0;" + "if r9 > 7 goto +0;" "r3 = r10;" /* force r7 to be precise, this also marks r6 */ "r3 += r7;" diff --git a/tools/testing/selftests/bpf/verifier/precise.c b/tools/testing/selftests/bpf/verifier/precise.c index 64d722199e8f..59a020c35647 100644 --- a/tools/testing/selftests/bpf/verifier/precise.c +++ b/tools/testing/selftests/bpf/verifier/precise.c @@ -106,7 +106,7 @@ mark_precise: frame0: regs=r2 stack= before 22\ mark_precise: frame0: parent state regs=r2 stack=:\ mark_precise: frame0: last_idx 20 first_idx 20\ - mark_precise: frame0: regs=r2,r9 stack= before 20\ + mark_precise: frame0: regs=r2 stack= before 20\ mark_precise: frame0: parent state regs=r2,r9 stack=:\ mark_precise: frame0: last_idx 19 first_idx 17\ mark_precise: frame0: regs=r2,r9 stack= before 19\ @@ -183,10 +183,10 @@ .prog_type = BPF_PROG_TYPE_XDP, .flags = BPF_F_TEST_STATE_FREQ, .errstr = "mark_precise: frame0: last_idx 7 first_idx 7\ - mark_precise: frame0: parent state regs=r4 stack=-8:\ + mark_precise: frame0: parent state regs=r4 stack=:\ mark_precise: frame0: last_idx 6 first_idx 4\ - mark_precise: frame0: regs=r4 stack=-8 before 6: (b7) r0 = -1\ - mark_precise: frame0: regs=r4 stack=-8 before 5: (79) r4 = *(u64 *)(r10 -8)\ + mark_precise: frame0: regs=r4 stack= before 6: (b7) r0 = -1\ + mark_precise: frame0: regs=r4 stack= before 5: (79) r4 = *(u64 *)(r10 -8)\ mark_precise: frame0: regs= stack=-8 before 4: (7b) *(u64 *)(r3 -8) = r0\ mark_precise: frame0: parent state regs=r0 stack=:\ mark_precise: frame0: last_idx 3 first_idx 3\ From patchwork Fri Jul 5 20:58:50 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eduard Zingerman X-Patchwork-Id: 13725538 X-Patchwork-Delegate: bpf@iogearbox.net Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12B0B1459F9 for ; Fri, 5 Jul 2024 20:59:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213150; cv=none; b=qZFXzwTXwyyuXViRha+6wBNMfxYueDF3jxXG7wpG8T17vCNRskPakdZH3HpFnwWDRmwZFjR1YVCX44iUY+j6RqDaIYlyFqHHpoUHkEf5LSszft2CkuY37IkP0yHZywKw0Eg2yzpohsxfBE4nlJ7VxgrUTm57q9ulTajfyWJtfyI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720213150; c=relaxed/simple; bh=TX4pt3jt6//jb5FavZnRh/kqZ88SIqQnCgOULnFrEb8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=u4OsSA+x+CHK1WH2OBe2QgCag64qe+ZB0DvhonV3ttVxmGgHOzuwQtCre6D8l9tjlr55kReVQVpevZ7G67aTxAPDtNJTBu6jFywQgdnG+uWmFm54GbvMaBv+GZeS+wUarXRO53MrA39sggN8dTjdII/xqPUQwndqDkMVjXQF7jk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=gnxDVQ2c; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="gnxDVQ2c" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-1fb3cf78fbdso11542975ad.1 for ; Fri, 05 Jul 2024 13:59:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1720213148; x=1720817948; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Q+2J22QjEqG7RedVQ+I6NCeL5gQ5Va/n0Fq4dvBpMQA=; b=gnxDVQ2cXxWG2E7iIjcUvIb0OJl2zVUxJD8muw+ulhAiUk8fJY7910fPHLUrE1Rdfu nsVKGVaZuB1VFPWi8uzx+FxWloL7AEE/hyC4LGYOuhGsfwrV1l4nHRlrHGtx3EnYf2w0 ivS5W9RAs/iso9/7GYovpwXw3aySdFMfDH/UHJCR5aP4aQ9DaMPYI4r7GcjL4H0aelS9 LCgr2cBdyZcnrn1gG1CgGEC2msbE+xSp7l/eBS99TelYQ07D7nLb884XSc/+JTg1G7tu XqmY8P8/0ryYRaL0B5xQTeq0zke73STGhimawqnHaXcSvSEe4IgACfGQsApKUi4S2ovc xRxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720213148; x=1720817948; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Q+2J22QjEqG7RedVQ+I6NCeL5gQ5Va/n0Fq4dvBpMQA=; b=CW+kdoieYWcaBlejsBFkFf22xis4YSkXmKRbnYfIrxoFak8cltzf+6rQYs3hCtJCYa 3I0SoYSmtzv3aWIh+Tql9gSYeqUauAJRKoPjF4UadiOOqrG/7rioj0HN9XlcHF42oL9v 4PQ85BTa+qn+VOhMxMTN9m8E8KM8kwVGSHzoBm7+RiCVZmPy6CClK0Cr6McIo347j7RK SbSCne0MkReXQlghQMsO0Xvocps3wCD6RFQMsiEN2Y8lrLMCPtCQ8+4BcbmtYbPUSsjg DrWjG4O/uXAv8sMI4759x/30Nge+jxaG9b081jjP2i4+brf5zlsD8J448notofjea6Wa IPqw== X-Gm-Message-State: AOJu0YzT5i8QkycmxvW2pBICerk3gvHzZ3M6xiH195Kvp2ib0Z4UAVYg thYOJct4KtCIgLNYq//woSo/QFv8EEVRTm+sTAeldq/lEpmhuDOgFFsdEJRS X-Google-Smtp-Source: AGHT+IGwvLjlxkEf/qnMeMyiexMMPYXGj4KLtYpv6uOiARwRRlrUGVuIDt2uNLRabLmRpEGRoFnQpw== X-Received: by 2002:a17:902:f541:b0:1fa:2b11:4583 with SMTP id d9443c01a7336-1fb33df623dmr48175745ad.4.1720213148063; Fri, 05 Jul 2024 13:59:08 -0700 (PDT) Received: from badger.. ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac11d8c52sm144767705ad.112.2024.07.05.13.59.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jul 2024 13:59:07 -0700 (PDT) From: Eduard Zingerman To: bpf@vger.kernel.org, ast@kernel.org Cc: andrii@kernel.org, daniel@iogearbox.net, martin.lau@linux.dev, kernel-team@fb.com, yonghong.song@linux.dev, sunhao.th@gmail.com, Eduard Zingerman Subject: [PATCH bpf-next v2 3/3] selftests/bpf: tests for per-insn find_equal_scalars() precision tracking Date: Fri, 5 Jul 2024 13:58:50 -0700 Message-ID: <20240705205851.2635794-4-eddyz87@gmail.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240705205851.2635794-1-eddyz87@gmail.com> References: <20240705205851.2635794-1-eddyz87@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Add a few test cases to verify precision tracking for scalars gaining range because of find_equal_scalars(): - check what happens when more than 6 registers might gain range in find_equal_scalars(); - check if precision is propagated correctly when operand of conditional jump gained range in find_equal_scalars() and one of linked registers is marked precise; - check if precision is propagated correctly when operand of conditional jump gained range in find_equal_scalars() and a other-linked operand of the conditional jump is marked precise; - add a minimized reproducer for precision tracking bug reported in [0]; - Check that mark_chain_precision() for one of the conditional jump operands does not trigger equal scalars precision propagation. [0] https://lore.kernel.org/bpf/CAEf4BzZ0xidVCqB47XnkXcNhkPWF6_nTV7yt+_Lf0kcFEut2Mg@mail.gmail.com/ Signed-off-by: Eduard Zingerman --- .../selftests/bpf/progs/verifier_scalar_ids.c | 165 ++++++++++++++++++ 1 file changed, 165 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c index 639db72b1c55..993c5affb3d7 100644 --- a/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c +++ b/tools/testing/selftests/bpf/progs/verifier_scalar_ids.c @@ -47,6 +47,72 @@ __naked void equal_scalars_bpf_k(void) : __clobber_all); } +/* Registers r{0,1,2} share same ID when 'if r1 > ...' insn is processed, + * check that verifier marks r{1,2} as precise while backtracking + * 'if r1 > ...' with r0 already marked. + */ +SEC("socket") +__success __log_level(2) +__flag(BPF_F_TEST_STATE_FREQ) +__msg("frame0: regs=r0 stack= before 5: (2d) if r1 > r3 goto pc+0") +__msg("frame0: parent state regs=r0,r1,r2,r3 stack=:") +__msg("frame0: regs=r0,r1,r2,r3 stack= before 4: (b7) r3 = 7") +__naked void equal_scalars_bpf_x_src(void) +{ + asm volatile ( + /* r0 = random number up to 0xff */ + "call %[bpf_ktime_get_ns];" + "r0 &= 0xff;" + /* tie r0.id == r1.id == r2.id */ + "r1 = r0;" + "r2 = r0;" + "r3 = 7;" + "if r1 > r3 goto +0;" + /* force r0 to be precise, this eventually marks r1 and r2 as + * precise as well because of shared IDs + */ + "r4 = r10;" + "r4 += r0;" + "r0 = 0;" + "exit;" + : + : __imm(bpf_ktime_get_ns) + : __clobber_all); +} + +/* Registers r{0,1,2} share same ID when 'if r1 > r3' insn is processed, + * check that verifier marks r{0,1,2} as precise while backtracking + * 'if r1 > r3' with r3 already marked. + */ +SEC("socket") +__success __log_level(2) +__flag(BPF_F_TEST_STATE_FREQ) +__msg("frame0: regs=r3 stack= before 5: (2d) if r1 > r3 goto pc+0") +__msg("frame0: parent state regs=r0,r1,r2,r3 stack=:") +__msg("frame0: regs=r0,r1,r2,r3 stack= before 4: (b7) r3 = 7") +__naked void equal_scalars_bpf_x_dst(void) +{ + asm volatile ( + /* r0 = random number up to 0xff */ + "call %[bpf_ktime_get_ns];" + "r0 &= 0xff;" + /* tie r0.id == r1.id == r2.id */ + "r1 = r0;" + "r2 = r0;" + "r3 = 7;" + "if r1 > r3 goto +0;" + /* force r0 to be precise, this eventually marks r1 and r2 as + * precise as well because of shared IDs + */ + "r4 = r10;" + "r4 += r3;" + "r0 = 0;" + "exit;" + : + : __imm(bpf_ktime_get_ns) + : __clobber_all); +} + /* Same as equal_scalars_bpf_k, but break one of the * links, note that r1 is absent from regs=... in __msg below. */ @@ -280,6 +346,105 @@ __naked void precision_two_ids(void) : __clobber_all); } +SEC("socket") +__success __log_level(2) +__flag(BPF_F_TEST_STATE_FREQ) +/* check thar r0 and r6 have different IDs after 'if', + * find_equal_scalars() can't tie more than 6 registers for a single insn. + */ +__msg("8: (25) if r0 > 0x7 goto pc+0 ; R0=scalar(id=1") +__msg("9: (bf) r6 = r6 ; R6_w=scalar(id=2") +/* check that r{0-5} are marked precise after 'if' */ +__msg("frame0: regs=r0 stack= before 8: (25) if r0 > 0x7 goto pc+0") +__msg("frame0: parent state regs=r0,r1,r2,r3,r4,r5 stack=:") +__naked void equal_scalars_too_many_regs(void) +{ + asm volatile ( + /* r0 = random number up to 0xff */ + "call %[bpf_ktime_get_ns];" + "r0 &= 0xff;" + /* tie r{0-6} IDs */ + "r1 = r0;" + "r2 = r0;" + "r3 = r0;" + "r4 = r0;" + "r5 = r0;" + "r6 = r0;" + /* propagate range for r{0-6} */ + "if r0 > 7 goto +0;" + /* make r6 appear in the log */ + "r6 = r6;" + /* force r0 to be precise, + * this would cause r{0-4} to be precise because of shared IDs + */ + "r7 = r10;" + "r7 += r0;" + "r0 = 0;" + "exit;" + : + : __imm(bpf_ktime_get_ns) + : __clobber_all); +} + +SEC("socket") +__failure __log_level(2) +__flag(BPF_F_TEST_STATE_FREQ) +__msg("regs=r7 stack= before 5: (3d) if r8 >= r0") +__msg("parent state regs=r0,r7,r8") +__msg("regs=r0,r7,r8 stack= before 4: (25) if r0 > 0x1") +__msg("div by zero") +__naked void equal_scalars_broken_link_2(void) +{ + asm volatile ( + "call %[bpf_get_prandom_u32];" + "r7 = r0;" + "r8 = r0;" + "call %[bpf_get_prandom_u32];" + "if r0 > 1 goto +0;" + /* r7.id == r8.id, + * thus r7 precision implies r8 precision, + * which implies r0 precision because of the conditional below. + */ + "if r8 >= r0 goto 1f;" + /* break id relation between r7 and r8 */ + "r8 += r8;" + /* make r7 precise */ + "if r7 == 0 goto 1f;" + "r0 /= 0;" +"1:" + "r0 = 42;" + "exit;" + : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +/* Check that mark_chain_precision() for one of the conditional jump + * operands does not trigger equal scalars precision propagation. + */ +SEC("socket") +__success __log_level(2) +__msg("3: (25) if r1 > 0x100 goto pc+0") +__msg("frame0: regs=r1 stack= before 2: (bf) r1 = r0") +__naked void cjmp_no_equal_scalars_trigger(void) +{ + asm volatile ( + /* r0 = random number up to 0xff */ + "call %[bpf_ktime_get_ns];" + "r0 &= 0xff;" + /* tie r0.id == r1.id */ + "r1 = r0;" + /* the jump below would be predicted, thus r1 would be marked precise, + * this should not imply precision mark for r0 + */ + "if r1 > 256 goto +0;" + "r0 = 0;" + "exit;" + : + : __imm(bpf_ktime_get_ns) + : __clobber_all); +} + /* Verify that check_ids() is used by regsafe() for scalars. * * r9 = ... some pointer with range X ...