From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 34CE6CD6E79 for ; Fri, 5 Jun 2026 14:54:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=7T10tbTpcV2pUBQyWyrHxm7GXYtp6nDFJhaWs/Lxnh8=; b=D+paCOV8R+t5lfFBp+GoXSlngK 378j4E6VtJSpMUwQCeOVyocbJY69HsgAxcGxQKhM8HMVNCkkbiMOCoPFLG/dmZKzivYnk0N5aMO18 rosAPE/qi6TUJTlvWctSwAyJmZDK21sKCktnv3wb2MvODffUVdcqeHCOHUoWZUQu44t9S2E0TrNGh bCVyhHn3IECln692t+VOFwQXH5q2IdNNOu4yfgGouw901LF7oQZZix/K4q/U7xwH5uuDSD4A29c1x 1bid3T+3MLgbyQICgAhLZ+Mta+3nQS+gRLDJUlw2uBfPwDCH3rtKkiNvrT27I+qOsIc5FCvKbyKG2 qe3rEAsA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wVVwZ-00000000kxB-1AfR; Fri, 05 Jun 2026 14:54:43 +0000 Received: from out-183.mta0.migadu.com ([2001:41d0:1004:224b::b7]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wVVwV-00000000kt7-0fG2 for linux-arm-kernel@lists.infradead.org; Fri, 05 Jun 2026 14:54:41 +0000 Message-ID: <78009c06-4233-4e0a-88ec-33eba10ad8b3@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780671264; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7T10tbTpcV2pUBQyWyrHxm7GXYtp6nDFJhaWs/Lxnh8=; b=BxFUAK/AN0wgD8eGGuFvdxWnrnCkHUxSLZUNCUu//z2V+cA/zvbouPYpYAlPSkzosrFZU4 J/W40RsQpiE5xjC0yjYu9DCCYN3v6ILmOEpt/EJFIv4gFx4ius1bqklwFG5NlxcYMFStI9 OVRzcmh7CdTWQmTPodFF0Il4jS6egCY= Date: Fri, 5 Jun 2026 07:54:10 -0700 MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v2 5/8] bpf, x86: emit KASAN checks into x86 JITed programs Content-Language: en-GB To: =?UTF-8?Q?Alexis_Lothor=C3=A9_=28eBPF_Foundation=29?= , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Jiri Olsa , John Fastabend , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Shuah Khan , Maxime Coquelin , Alexandre Torgue , Ihor Solodrai Cc: ebpf@linuxfoundation.org, Bastien Curutchet , Thomas Petazzoni , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org References: <20260604-kasan-v2-0-c066e627fda8@bootlin.com> <20260604-kasan-v2-5-c066e627fda8@bootlin.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20260604-kasan-v2-5-c066e627fda8@bootlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260605_075440_115205_0D98AC33 X-CRM114-Status: GOOD ( 26.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 6/4/26 1:22 PM, Alexis Lothoré (eBPF Foundation) wrote: > Insert KASAN shadow memory checks before memory load and store > operations in JIT-compiled BPF programs. This helps detect memory safety > bugs such as use-after-free and out-of-bounds accesses at runtime. > > The main instructions being targeted are BPF_ST, BPF_STX and BPF_LDX, > but not all of them are being instrumented: > - if the load/store instruction is in fact accessing the program stack, > emit_kasan_check silently skips the instrumentation, as we already > have page guards to monitor stack accesses. > - if the load/store instruction is a BPF_PROBE_MEM or a BPF_PROBE_ATOMIC > instruction, we do not instrument it, as the passed address can fault > (hence the custom fault management with BPF_PROBE_XXX instructions), > and so the corresponding kasan check could fault as well. > > Signed-off-by: Alexis Lothoré (eBPF Foundation) > --- > Changes in v2: > - support BPF_ATOMICS > - support BPF_ST > - make sure to systematically pass correct instruction to kasan check > --- > arch/x86/net/bpf_jit_comp.c | 63 ++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 53 insertions(+), 10 deletions(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index 943a0f315cf2..cb3c03edc4bd 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -1516,17 +1516,30 @@ static int emit_atomic_rmw_index(u8 **pprog, u32 atomic_op, u32 size, > return 0; > } > > -static int emit_atomic_ld_st(u8 **pprog, u32 atomic_op, u32 dst_reg, > - u32 src_reg, s16 off, u8 bpf_size) > +static int emit_atomic_ld_st(u8 **pprog, struct bpf_insn *insn, u8 *ip, > + u32 dst_reg, u32 src_reg, bool accesses_stack_only) > { > + u32 atomic_op = insn->imm; > + int err; > + > switch (atomic_op) { > case BPF_LOAD_ACQ: > + err = emit_kasan_check(pprog, src_reg, insn, ip, false, > + accesses_stack_only); > + if (err) > + return err; > /* dst_reg = smp_load_acquire(src_reg + off16) */ > - emit_ldx(pprog, bpf_size, dst_reg, src_reg, off); > + emit_ldx(pprog, BPF_SIZE(insn->code), dst_reg, src_reg, > + insn->off); > break; > case BPF_STORE_REL: > + err = emit_kasan_check(pprog, dst_reg, insn, ip, true, > + accesses_stack_only); > + if (err) > + return err; > /* smp_store_release(dst_reg + off16, src_reg) */ > - emit_stx(pprog, bpf_size, dst_reg, src_reg, off); > + emit_stx(pprog, BPF_SIZE(insn->code), dst_reg, src_reg, > + insn->off); > break; > default: > pr_err("bpf_jit: unknown atomic load/store opcode %02x\n", > @@ -1904,6 +1917,7 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > const s32 imm32 = insn->imm; > u32 dst_reg = insn->dst_reg; > u32 src_reg = insn->src_reg; > + bool accesses_stack_only; > u8 b2 = 0, b3 = 0; > u8 *start_of_ldx; > s64 jmp_offset; > @@ -1924,6 +1938,8 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > EMIT_ENDBR(); > > ip = image + addrs[i - 1] + (prog - temp); > + accesses_stack_only = > + bpf_insn_accesses_stack_only(env, bpf_prog, i - 1); > > switch (insn->code) { > /* ALU */ > @@ -2304,6 +2320,10 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > case BPF_ST | BPF_MEM | BPF_H: > case BPF_ST | BPF_MEM | BPF_W: > case BPF_ST | BPF_MEM | BPF_DW: > + err = emit_kasan_check(&prog, dst_reg, insn, ip, true, > + accesses_stack_only); > + if (err) > + return err; > switch (BPF_SIZE(insn->code)) { > case BPF_B: > if (is_ereg(dst_reg)) > @@ -2369,6 +2389,10 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > insn_off = outgoing_arg_base - outgoing_rsp - insn_off - 16; > dst_reg = BPF_REG_FP; > } > + err = emit_kasan_check(&prog, dst_reg, insn, ip, true, > + accesses_stack_only); > + if (err) > + return err; > emit_stx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off); > break; > > @@ -2530,6 +2554,12 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > /* populate jmp_offset for JAE above to jump to start_of_ldx */ > start_of_ldx = prog; > end_of_jmp[-1] = start_of_ldx - end_of_jmp; > + } else { > + err = emit_kasan_check(&prog, src_reg, insn, ip, > + false, > + accesses_stack_only); > + if (err) > + return err; > } > if (BPF_MODE(insn->code) == BPF_PROBE_MEMSX || > BPF_MODE(insn->code) == BPF_MEMSX) > @@ -2592,13 +2622,13 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > fallthrough; > case BPF_STX | BPF_ATOMIC | BPF_W: > case BPF_STX | BPF_ATOMIC | BPF_DW: > + bool is64 = BPF_SIZE(insn->code) == BPF_DW; > + u32 real_src_reg = src_reg; > + u32 real_dst_reg = dst_reg; With llvm23, I got the following build failure: /home/yhs/work/bpf-next/arch/x86/net/bpf_jit_comp.c:2625:4: error: label followed by a declaration is a C23 extension [-Werror,-Wc23-extensions] 2625 | bool is64 = BPF_SIZE(insn->code) == BPF_DW; | ^ 1 error generated. The below is a fix: diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index cb3c03edc4bd..61faf8d8f157 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -2621,7 +2621,7 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * } fallthrough; case BPF_STX | BPF_ATOMIC | BPF_W: - case BPF_STX | BPF_ATOMIC | BPF_DW: + case BPF_STX | BPF_ATOMIC | BPF_DW: { bool is64 = BPF_SIZE(insn->code) == BPF_DW; u32 real_src_reg = src_reg; u32 real_dst_reg = dst_reg; @@ -2695,6 +2695,7 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * if (err) return err; break; + } case BPF_STX | BPF_PROBE_ATOMIC | BPF_B: case BPF_STX | BPF_PROBE_ATOMIC | BPF_H: > + u8 *branch_target; > if (insn->imm == (BPF_AND | BPF_FETCH) || > insn->imm == (BPF_OR | BPF_FETCH) || > insn->imm == (BPF_XOR | BPF_FETCH)) { > - bool is64 = BPF_SIZE(insn->code) == BPF_DW; > - u32 real_src_reg = src_reg; > - u32 real_dst_reg = dst_reg; > - u8 *branch_target; > > /* > * Can't be implemented with a single x86 insn. > @@ -2612,7 +2642,19 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > if (dst_reg == BPF_REG_0) > real_dst_reg = BPF_REG_AX; > > + ip += 3; > + } > + if (!bpf_atomic_is_load_store(insn)) { > + err = emit_kasan_check(&prog, real_dst_reg, > + insn, ip, false, > + accesses_stack_only); > + if (err) > + return err; > branch_target = prog; > + } > + if (insn->imm == (BPF_AND | BPF_FETCH) || > + insn->imm == (BPF_OR | BPF_FETCH) || > + insn->imm == (BPF_XOR | BPF_FETCH)) { > /* Load old value */ > emit_ldx(&prog, BPF_SIZE(insn->code), > BPF_REG_0, real_dst_reg, insn->off); > @@ -2644,8 +2686,9 @@ static int do_jit(struct bpf_verifier_env *env, struct bpf_prog *bpf_prog, int * > } > > if (bpf_atomic_is_load_store(insn)) > - err = emit_atomic_ld_st(&prog, insn->imm, dst_reg, src_reg, > - insn->off, BPF_SIZE(insn->code)); > + err = emit_atomic_ld_st(&prog, insn, ip, > + dst_reg, src_reg, > + accesses_stack_only); > else > err = emit_atomic_rmw(&prog, insn->imm, dst_reg, src_reg, > insn->off, BPF_SIZE(insn->code)); >