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SubjectRe: [kernel-hardening] [RFC V2 2/6] lib: vsprintf: whitelist stack traces
On Wed, Oct 04, 2017 at 11:02:55AM +0200, Greg KH wrote:
> On Wed, Oct 04, 2017 at 09:58:10AM +0100, Will Deacon wrote:
> > On Wed, Oct 04, 2017 at 10:56:57AM +0200, Greg KH wrote:
> > > 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?
> > >
> > > Because you really want the real value? Seems to make sense to me...
> >
> > Just seems like anybody debugging the kernel using pr_debug can probably
> > change /proc/sys/kernel/kptr_restrict...
>
> Ok, fair enough :)

For what its worth I agree with Will.

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