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SubjectRe: [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces
On Mon, Oct 02, 2017 at 11:42:05AM +0100, Will Deacon wrote:
> 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?

Thanks for the review Will. I did not do the original work on this series so do not know the
original intent behind this change. I tend to agree with your comment. Will remove this change for
v3.

> > 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

Point noted.

thanks,
Tobin.

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