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

[Xiaoming Ni]

ping

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@xxxxxxxxxx>
>
> -------
> 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@xxxxxxxxxx/
>    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);