On Thu, May 20, 2021 at 12:00 PM Mark Rutland [off-list ref] wrote:

On the kernel side, we use a unique IA key per kernel thread, and while
this must remain the same *for that kernel thread*, the kernel IA key
should differ across kernel threads when a fork() occurs.

Thank you for the clarification.

I think you're trying to use the keys in a different way than upstream
intends to, and we do not need this change as-is.

So NAK to this patch as it stands.

Given the above discussion, I agree with the NAK.

quoted

---
 arch/arm64/include/asm/pointer_auth.h | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index d50416be99be..9748413e72fd 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h

@@ -69,10 +69,13 @@ static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
      ptrauth_keys_install_user(keys);
 }

-static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
+static __always_inline void
+ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
 {
-     if (system_supports_address_auth())
-             get_random_bytes(&keys->apia, sizeof(keys->apia));
+     if (keys->apia.lo == 0 && keys->apia.hi == 0) {
+             if (system_supports_address_auth())
+                     get_random_bytes(&keys->apia, sizeof(keys->apia));
+     }
 }

 static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
--

2.31.1

-- 
Derrick McKee
Phone: (703) 957-9362
Email: derrick.mckee@gmail.com

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