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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=JGIhTX1iYBMgF744IBDkziq2Q7vA4MuCaT2yYSxn/kE=; b=I9cozBk7F5/sDL8Kj5K/sw2ZQOKTsBMX0kT/8izceLWaJOgs26YVPBaqUgE6XSeUad J3EURnYqNY/U1FCmdduvrLZYmL1BsBj/nqbuOzMDZvOfhQKMD1Ry80Nfxu9LqhiMw4sK GO7bABE4xa1IjCgoVfN1OrT8AVMTBML5AG82wNZ+wofST82wAHAK6dVB83z9Ji4VCK9e IaHdVYqy7GM0h9g3uqq3GvHyu1bRuuuM0osnGuYEXsD6VUrcUxi7u6iYhqB7y9d7joFx YbKYCJRmG+6CN0kmQoTQpbmj7+d/GBdP3dJ5dTL5grXFoJ7N2O0CTX1jIcnD2g/FHlna F3SA== X-Gm-Message-State: AOAM530Ta9F8WHTyz2pKJPfsA5WzFgw1SY3yJ07dauOf0r72wvAyydHj t/SExBfM3BVBjJuMgreMLHCZBHYHJcG3iF7Qv3I= X-Google-Smtp-Source: ABdhPJxet7rQw0y6nxIveHE7CF+nZHHpGRcztGpne0cnSSXMkm5i1vlorbi4e29hi04uoltOpCouFuJQaEP8UfOxQco= X-Received: by 2002:a25:e701:: with SMTP id e1mr6632254ybh.510.1605068083120; Tue, 10 Nov 2020 20:14:43 -0800 (PST) MIME-Version: 1.0 References: <1605063541-25424-1-git-send-email-kaixuxia@tencent.com> In-Reply-To: <1605063541-25424-1-git-send-email-kaixuxia@tencent.com> From: Andrii Nakryiko Date: Tue, 10 Nov 2020 20:14:32 -0800 Message-ID: Subject: Re: [PATCH v2] bpf: Fix unsigned 'datasec_id' compared with zero in check_pseudo_btf_id To: xiakaixu1987@gmail.com Cc: Alexei Starovoitov , Daniel Borkmann , Martin Lau , Song Liu , Yonghong Song , Andrii Nakryiko , john fastabend , KP Singh , Networking , bpf , open list , Kaixu Xia Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 10, 2020 at 6:59 PM wrote: > > From: Kaixu Xia > > The unsigned variable datasec_id is assigned a return value from the call > to check_pseudo_btf_id(), which may return negative error code. > > Fixes coccicheck warning: > > ./kernel/bpf/verifier.c:9616:5-15: WARNING: Unsigned expression compared with zero: datasec_id > 0 > > Reported-by: Tosk Robot > Signed-off-by: Kaixu Xia > --- > v2: > -split out datasec_id definition into a separate line. > > kernel/bpf/verifier.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 6200519582a6..3fea4fc04e94 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -9572,7 +9572,8 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env, > struct bpf_insn *insn, > struct bpf_insn_aux_data *aux) > { > - u32 datasec_id, type, id = insn->imm; > + s32 datasec_id; > + u32 type, id = insn->imm; > const struct btf_var_secinfo *vsi; > const struct btf_type *datasec; > const struct btf_type *t; > -- > 2.20.0 > It would look a bit cleaner if you did it this way: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 10da26e55130..f674b1403637 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9585,12 +9585,13 @@ static int check_pseudo_btf_id(struct bpf_verifier_env *env, struct bpf_insn *insn, struct bpf_insn_aux_data *aux) { - u32 datasec_id, type, id = insn->imm; const struct btf_var_secinfo *vsi; const struct btf_type *datasec; const struct btf_type *t; const char *sym_name; bool percpu = false; + u32 type, id = insn->imm; + s32 datasec_id; u64 addr; int i;