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Date:   Mon, 27 Sep 2021 00:36:12 -0700
From:   "H. Peter Anvin" <hpa@zytor.com>
To:     Ian Rogers <irogers@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        linux-kernel@vger.kernel.org,
        Adrian Hunter <adrian.hunter@intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        David Laight <David.Laight@aculab.com>
CC:     Numfor Mbiziwo-Tiapo <nums@google.com>
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_v4=5D_x86/insn=2C_tools/x86=3A_F?= =?US-ASCII?Q?ix_some_potential_undefined_behavior=2E?=
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We have get_unaligned() for a reason=2E

On September 23, 2021 9:18:43 AM PDT, Ian Rogers <irogers@google=2Ecom> wr=
ote:
>From: Numfor Mbiziwo-Tiapo <nums@google=2Ecom>
>
>Don't perform unaligned loads in __get_next and __peek_nbyte_next as
>these are forms of undefined behavior=2E
>
>These problems were identified using the undefined behavior sanitizer
>(ubsan) with the tools version of the code and perf test=2E Part of this
>patch was previously posted here:
>https://lore=2Ekernel=2Eorg/lkml/20190724184512=2E162887-4-nums@google=2E=
com/
>
>v4=2E Fixes a typo=2E
>
>v3=2E Is a rebase picking up a fix for big endian architectures=2E
>
>v2=2E removes the validate_next check and merges the 2 changes into one a=
s
>requested by Masami Hiramatsu <mhiramat@kernel=2Eorg>
>
>Signed-off-by: Ian Rogers <irogers@google=2Ecom>
>Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google=2Ecom>
>Acked-by: Masami Hiramatsu <mhiramat@kernel=2Eorg>
>---
> arch/x86/lib/insn=2Ec       | 4 ++--
> tools/arch/x86/lib/insn=2Ec | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/arch/x86/lib/insn=2Ec b/arch/x86/lib/insn=2Ec
>index 058f19b20465=2E=2Ec565def611e2 100644
>--- a/arch/x86/lib/insn=2Ec
>+++ b/arch/x86/lib/insn=2Ec
>@@ -37,10 +37,10 @@
> 	((insn)->next_byte + sizeof(t) + n <=3D (insn)->end_kaddr)
>=20
> #define __get_next(t, insn)	\
>-	({ t r =3D *(t*)insn->next_byte; insn->next_byte +=3D sizeof(t); leXX_t=
o_cpu(t, r); })
>+	({ t r; memcpy(&r, insn->next_byte, sizeof(t)); insn->next_byte +=3D si=
zeof(t); leXX_to_cpu(t, r); })
>=20
> #define __peek_nbyte_next(t, insn, n)	\
>-	({ t r =3D *(t*)((insn)->next_byte + n); leXX_to_cpu(t, r); })
>+	({ t r; memcpy(&r, (insn)->next_byte + n, sizeof(t)); leXX_to_cpu(t, r)=
; })
>=20
> #define get_next(t, insn)	\
> 	({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t=
, insn); })
>diff --git a/tools/arch/x86/lib/insn=2Ec b/tools/arch/x86/lib/insn=2Ec
>index c41f95815480=2E=2E797699462cd8 100644
>--- a/tools/arch/x86/lib/insn=2Ec
>+++ b/tools/arch/x86/lib/insn=2Ec
>@@ -37,10 +37,10 @@
> 	((insn)->next_byte + sizeof(t) + n <=3D (insn)->end_kaddr)
>=20
> #define __get_next(t, insn)	\
>-	({ t r =3D *(t*)insn->next_byte; insn->next_byte +=3D sizeof(t); leXX_t=
o_cpu(t, r); })
>+	({ t r; memcpy(&r, insn->next_byte, sizeof(t)); insn->next_byte +=3D si=
zeof(t); leXX_to_cpu(t, r); })
>=20
> #define __peek_nbyte_next(t, insn, n)	\
>-	({ t r =3D *(t*)((insn)->next_byte + n); leXX_to_cpu(t, r); })
>+	({ t r; memcpy(&r, (insn)->next_byte + n, sizeof(t)); leXX_to_cpu(t, r)=
; })
>=20
> #define get_next(t, insn)	\
> 	({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t=
, insn); })

--=20
Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E