linux-kernel - Re: [PATCH 1/2] ANDROID: cfi: enable sanitize for cfi.c

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Message-ID: <20220701021042.48037-1-haibo.li@mediatek.com>
Date:   Fri, 1 Jul 2022 10:10:42 +0800
From:   Haibo Li <haibo.li@...iatek.com>
To:     <samitolvanen@...gle.com>
CC:     <andrealmeid@...lia.com>, <atomlin@...hat.com>,
        <christophe.leroy@...roup.eu>, <dmitry.torokhov@...il.com>,
        <haibo.li@...iatek.com>, <jgross@...e.com>,
        <keescook@...omium.org>, <lecopzer.chen@...iatek.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <llvm@...ts.linux.dev>,
        <matthias.bgg@...il.com>, <mcgrof@...nel.org>,
        <mhiramat@...nel.org>, <nathan@...nel.org>,
        <ndesaulniers@...gle.com>, <peterz@...radead.org>,
        <xiaoming.yu@...iatek.com>, <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH 1/2] ANDROID: cfi: enable sanitize for cfi.c

> On Thu, Jun 30, 2022 at 2:47 AM Haibo Li <haibo.li@...iatek.com> wrote:
> >
> > currenly,cfi.c is excluded from cfi sanitize because of cfi handler.
> > The side effect is that we can not transfer function pointer to other
> > files which enable cfi sanitize.
> >
> > Enable cfi sanitize for cfi.c and bypass cfi check for
> > __cfi_slowpath_diag
> >
> > Signed-off-by: Haibo Li <haibo.li@...iatek.com>
> > Signed-off-by: Lecopzer Chen <lecopzer.chen@...iatek.com>
> > ---
> >  kernel/Makefile | 3 ---
> >  kernel/cfi.c    | 8 +++++++-
> >  2 files changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/Makefile b/kernel/Makefile index
> > a7e1f49ab2b3..a997bef1a200 100644
> > --- a/kernel/Makefile
> > +++ b/kernel/Makefile
> > @@ -40,9 +40,6 @@ KCSAN_SANITIZE_kcov.o := n
> UBSAN_SANITIZE_kcov.o :=
> > n  CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack)
> > -fno-stack-protector
> >
> > -# Don't instrument error handlers
> > -CFLAGS_REMOVE_cfi.o := $(CC_FLAGS_CFI)
> > -
> >  obj-y += sched/
> >  obj-y += locking/
> >  obj-y += power/
> > diff --git a/kernel/cfi.c b/kernel/cfi.c index
> > 08102d19ec15..456771c8e454 100644
> > --- a/kernel/cfi.c
> > +++ b/kernel/cfi.c
> > @@ -311,7 +311,7 @@ static inline cfi_check_fn find_check_fn(unsigned
> long ptr)
> >         return fn;
> >  }
> >
> > -void __cfi_slowpath_diag(uint64_t id, void *ptr, void *diag)
> > +static inline void __nocfi _run_cfi_check(u64 id, void *ptr, void
> > +*diag)
> >  {
> >         cfi_check_fn fn = find_check_fn((unsigned long)ptr);
> >
> > @@ -320,6 +320,12 @@ void __cfi_slowpath_diag(uint64_t id, void *ptr,
> void *diag)
> >         else /* Don't allow unchecked modules */
> >                 handle_cfi_failure(ptr);  }
> > +
> > +void __cfi_slowpath_diag(u64 id, void *ptr, void *diag) {
> > +       /*run cfi check without cfi sanitize to avoid calling cfi handler
> recursively*/
> > +       _run_cfi_check(id, ptr, diag); }
> >  EXPORT_SYMBOL(__cfi_slowpath_diag);
> 
> You can just add __nocfi to __cfi_slowpath_diag, right? There's no need for the
> separate function.

    You are right.Now there is no requirement for constant crc of __cfi_slowpath_diag.
I will change it later.