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[kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces

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  [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces "Tobin C. Harding" <me@tobin.cc> - 2017-10-01 02:10 +0200
    Re: [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack  traces Will Deacon <will.deacon@arm.com> - 2017-10-02 12:50 +0200

#1742711 — [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces

Use the %pP functionality to explicitly allow kernel
pointers to be logged for stack traces.

Signed-off-by: Tobin C. Harding <me@tobin.cc>
---
 arch/arm64/kernel/traps.c | 4 ++--
 kernel/printk/printk.c    | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 5ea4b85..fe09660 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -147,7 +147,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	struct stackframe frame;
 	int skip;
 
-	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+	pr_debug("%s(regs = %pP tsk = %pP)\n", __func__, regs, tsk);
 
 	if (!tsk)
 		tsk = current;
@@ -233,7 +233,7 @@ static int __die(const char *str, int err, struct pt_regs *regs)
 
 	print_modules();
 	__show_regs(regs);
-	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
+	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%pP)\n",
 		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk),
 		 end_of_stack(tsk));
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 512f7c2..af0bc8e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3142,7 +3142,7 @@ void show_regs_print_info(const char *log_lvl)
 {
 	dump_stack_print_info(log_lvl);
 
-	printk("%stask: %p task.stack: %p\n",
+	printk("%stask: %pP task.stack: %pP\n",
 	       log_lvl, current, task_stack_page(current));
 }
 
-- 
2.7.4

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#1743110 — Re: [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces

On Sun, Oct 01, 2017 at 11:06:46AM +1100, Tobin C. Harding wrote:
> Use the %pP functionality to explicitly allow kernel
> pointers to be logged for stack traces.
> 
> Signed-off-by: Tobin C. Harding <me@tobin.cc>
> ---
>  arch/arm64/kernel/traps.c | 4 ++--
>  kernel/printk/printk.c    | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 5ea4b85..fe09660 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -147,7 +147,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>  	struct stackframe frame;
>  	int skip;
>  
> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
> +	pr_debug("%s(regs = %pP tsk = %pP)\n", __func__, regs, tsk);

Why do we care for pr_debug?

>  	if (!tsk)
>  		tsk = current;
> @@ -233,7 +233,7 @@ static int __die(const char *str, int err, struct pt_regs *regs)
>  
>  	print_modules();
>  	__show_regs(regs);
> -	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%p)\n",
> +	pr_emerg("Process %.*s (pid: %d, stack limit = 0x%pP)\n",
>  		 TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk),
>  		 end_of_stack(tsk));
>  
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 512f7c2..af0bc8e 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c

It probably makes sense to keep this separate from arch/ changes

Will

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