It doesn't make sense to issue prctl(PR_PAC_RESET_KEYS) on a
compat task because the 32-bit instruction set does not offer PAuth
instructions. For consistency with other 64-bit only prctls such as
{SET,GET}_TAGGED_ADDR_CTRL, reject the prctl on compat tasks.
Although this is a userspace-visible change, maybe it isn't too late
to make this change given that the hardware isn't available yet and
it's very unlikely that anyone has 32-bit software that actually
depends on this succeeding.
Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Ie885a1ff84ab498cc9f62d6451e9f2cfd4b1d06a
Link: https://lore.kernel.org/r/20201014052430.11630-1-pcc@google.com
[will: Do the same for the SVE prctl()s]
Signed-off-by: Will Deacon <will@kernel.org>
As we're going to enable pointer auth within the kernel and use a
different APIAKey for the kernel itself, so move the user APIAKey
switch to EL0 exception return.
The other 4 keys could remain switched during task switch, but are also
moved to keep things consistent.
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: commit msg, re-positioned the patch, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
We currently enable ptrauth for userspace, but do not use it within the
kernel. We're going to enable it for the kernel, and will need to manage
a separate set of ptrauth keys for the kernel.
We currently keep all 5 keys in struct ptrauth_keys. However, as the
kernel will only need to use 1 key, it is a bit wasteful to allocate a
whole ptrauth_keys struct for every thread.
Therefore, a subsequent patch will define a separate struct, with only 1
key, for the kernel. In preparation for that, rename the existing struct
(and associated macros and functions) to reflect that they are specific
to userspace.
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-positioned the patch to reduce the diff]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
We don't need to get at the per-thread keys from assembly at all, so
they can live alongside the rest of the per-thread register state in
thread_struct instead of thread_info.
This will also allow straighforward whitelisting of the keys for
hardened usercopy should we expose them via a ptrace request later on.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Add an arm64-specific prctl to allow a thread to reinitialize its
pointer authentication keys to random values. This can be useful when
exec() is not used for starting new processes, to ensure that different
processes still have different keys.
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
