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Message-ID: <20191119214351.GQ3079@worktop.programming.kicks-ass.net>
Date: Tue, 19 Nov 2019 22:43:51 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Kees Cook <keescook@...omium.org>
Cc: Tianlin Li <tli@...italocean.com>, kernel-hardening@...ts.openwall.com,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Greentime Hu <green.hu@...il.com>,
Vincent Chen <deanbo422@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>,
x86@...nel.org, Jessica Yu <jeyu@...nel.org>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Jiri Kosina <jikos@...nel.org>, Miroslav Benes <mbenes@...e.cz>,
Petr Mladek <pmladek@...e.com>,
Joe Lawrence <joe.lawrence@...hat.com>
Subject: Re: [RFC PATCH] kernel/module: have the callers of set_memory_*()
check the return value
On Tue, Nov 19, 2019 at 09:07:34AM -0800, Kees Cook wrote:
> > diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
> > index bda949fd84e8..7ea1338821d6 100644
> > --- a/arch/arm/kernel/ftrace.c
> > +++ b/arch/arm/kernel/ftrace.c
> > @@ -59,13 +59,15 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
> >
> > int ftrace_arch_code_modify_prepare(void)
> > {
> > - set_all_modules_text_rw();
> > - return 0;
> > + return set_all_modules_text_rw();
> > }
> >
> > int ftrace_arch_code_modify_post_process(void)
> > {
> > - set_all_modules_text_ro();
> > + int ret;
>
> Blank line here...
>
> > + ret = set_all_modules_text_ro();
> > + if (ret)
> > + return ret;
> > /* Make sure any TLB misses during machine stop are cleared. */
> > flush_tlb_all();
> > return 0;
>
> Are callers of these ftrace functions checking return values too?
Aside from the fact that I just deleted the set_all_modules_text_*()
functions, ftrace actually does check the return value. It prvides a
nice WARN and kills ftrace dead.
> > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
> > index 171773257974..97a89c38f6b9 100644
> > --- a/arch/arm64/kernel/ftrace.c
> > +++ b/arch/arm64/kernel/ftrace.c
> > @@ -115,9 +115,11 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> > }
> >
> > /* point the trampoline to our ftrace entry point */
> > - module_disable_ro(mod);
> > + if (module_disable_ro(mod))
> > + return -EINVAL;
> > *dst = trampoline;
> > - module_enable_ro(mod, true);
> > + if (module_enable_ro(mod, true))
> > + return -EINVAL;
> >
> > /*
> > * Ensure updated trampoline is visible to instruction
Patching dead code again:
https://lkml.kernel.org/r/20191029165832.33606-5-mark.rutland@arm.com
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