On Mon, Nov 27, 2017 at 3:40 PM, Tobin C. Harding <me@xxxxxxxx> wrote: > Linus, > > I know you are bored of this patch set already and this pits your vast > experience against my eight months kernel dev experience ;) > > I humbly maintain that hashing %p and suggesting people use %x > _correctly_ isn't a WIN solution. > > Please don't go easy on me because I'm new, if I'm out of line - say > so. > > This set is based on the following assumptions. > > 1. We now have leaking_addresses.pl illuminating leaking addresses. > 2. We have no _clear_ strategy for fixing leaks once found. > 3. We do not have a proposed non opt-in solution. > 4. There is a distinct use case for this specifier. > > Patch 1: Corrects the docs for %pK. > > Patch 2: Refactors %pK code out of pointer() into helper function. > > Patch 3: Adds specifier %px, small 'x' was chosen because the hashed hex > value is printed in lower case. > > Patch 4/5: Provides example usage of new specifier. > > The hashing code is based on the work done hashing %p during 4.14 dev > cycle. > > Finally, with this patch set in place, we have the added benefit that > newbies (me) can quietly go around the kernel 'sweeping up' after > leaking addresses. This as apposed to using a hammer and hashing all > %p. And if this is deemed too little and too slow we can always search > and replace '%p' with '%px'. How does this opt-in to %px help? We'll still have %p everywhere. :( Why not invert this? %p is hashed and %px is the old %p? Then we can move %x users to %px. I'd still like to see a default-on solution for this class of leaks... -Kees > > thanks, > Tobin. > > Tobin C. Harding (5): > docs: correct documentation for %pK > vsprintf: refactor pK code out of pointer() > vsprintf: add specifier %px, unique identifier > KVM: use %px to print token identifier > vfio_pci: use %px to print token identifier > > Documentation/printk-formats.txt | 2 +- > drivers/vfio/pci/vfio_pci_intrs.c | 2 +- > lib/test_printf.c | 74 +++++++++++++++++ > lib/vsprintf.c | 166 ++++++++++++++++++++++++++++---------- > scripts/checkpatch.pl | 2 +- > virt/kvm/eventfd.c | 2 +- > 6 files changed, 202 insertions(+), 46 deletions(-) > > -- > 2.7.4 > -- Kees Cook Pixel Security