linux-kernel - Re: ping //Re: [PATCH v2] arm:traps: Don't print stack or raw PC/LR hex values in backtraces

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Date:   Mon, 26 Oct 2020 17:59:05 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Xiaoming Ni <nixiaoming@...wei.com>
Cc:     dima@...sta.com, will@...nel.org, jpoimboe@...hat.com,
        akpm@...ux-foundation.org, christian.brauner@...ntu.com,
        viro@...iv.linux.org.uk, ldufour@...ux.ibm.com, amanieu@...il.com,
        walken@...gle.com, ben.dooks@...ethink.co.uk, tglx@...utronix.de,
        bigeasy@...utronix.de, mingo@...nel.org,
        vincent.whitchurch@...s.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, wangle6@...wei.com,
        luohaizheng@...wei.com
Subject: Re: ping //Re: [PATCH v2] arm:traps: Don't print stack or raw PC/LR
 hex values in backtraces

On Mon, Oct 26, 2020 at 02:33:10PM +0800, Xiaoming Ni wrote:
> ping

The arm tree was closed due to the merge window, and thus patches do
not get applied at that point. Plus I tend not to review development
patches during the merge window.

> On 2020/10/16 10:31, Xiaoming Ni wrote:
> > Printing raw pointer values in backtraces has potential security
> > implications and are of questionable value anyway.
> > 
> > This patch follows x86 and arm64's lead and removes the "Exception stack:"
> > dump from kernel backtraces:
> > 	commit a25ffd3a6302a6 ("arm64: traps: Don't print stack or raw
> > 	 PC/LR values in backtraces")
> > 	commit bb5e5ce545f203 ("x86/dumpstack: Remove kernel text
> > 	 addresses from stack dump")
> > 
> > Signed-off-by: Xiaoming Ni <nixiaoming@...wei.com>
> > 
> > -------
> > v2:
> >   Delete [<hex numbers>] from the stack according to the email discussion
> >   in patch V1, Other information processing will be discussed in subsequent
> >   patches.
> > 
> > v1: https://lore.kernel.org/lkml/20201009075957.110017-1-nixiaoming@huawei.com/
> >    1. Don't print stack or raw PC/LR hex values in backtraces
> >    2. Don't print stack mem in backtraces
> >    3. if (!panic_on_oops), Don't print stack mem in __die()
> > ---
> >   arch/arm/kernel/process.c | 3 +--
> >   arch/arm/kernel/traps.c   | 4 ++--
> >   2 files changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> > index 8e6ace03e960..71c9e5597d39 100644
> > --- a/arch/arm/kernel/process.c
> > +++ b/arch/arm/kernel/process.c
> > @@ -121,8 +121,7 @@ void __show_regs(struct pt_regs *regs)
> >   	printk("PC is at %pS\n", (void *)instruction_pointer(regs));
> >   	printk("LR is at %pS\n", (void *)regs->ARM_lr);
> > -	printk("pc : [<%08lx>]    lr : [<%08lx>]    psr: %08lx\n",
> > -	       regs->ARM_pc, regs->ARM_lr, regs->ARM_cpsr);
> > +	printk("psr: %08lx\n", regs->ARM_cpsr);
> >   	printk("sp : %08lx  ip : %08lx  fp : %08lx\n",
> >   	       regs->ARM_sp, regs->ARM_ip, regs->ARM_fp);
> >   	printk("r10: %08lx  r9 : %08lx  r8 : %08lx\n",
> > diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> > index 17d5a785df28..911bbf164875 100644
> > --- a/arch/arm/kernel/traps.c
> > +++ b/arch/arm/kernel/traps.c
> > @@ -68,8 +68,8 @@ void dump_backtrace_entry(unsigned long where, unsigned long from,
> >   	unsigned long end = frame + 4 + sizeof(struct pt_regs);
> >   #ifdef CONFIG_KALLSYMS
> > -	printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
> > -		loglvl, where, (void *)where, from, (void *)from);
> > +	printk("%s (%ps) from (%pS)\n",
> > +		loglvl, (void *)where, (void *)from);
> >   #else
> >   	printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
> >   		loglvl, where, from);
> > 
> 
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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