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authorMark Rutland <mark.rutland@arm.com>2020-04-21 13:10:14 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2020-04-21 15:52:56 +0100
commit3fabb43818c9bfe7c4084badfa21d4e8187021a6 (patch)
tree6e72ca8a70648b08c5b03fb984374e406701ad37 /arch
parentae83d0b416db002fe95601e7f97f64b59514d936 (diff)
arm64: sync kernel APIAKey when installing
A direct write to a APxxKey_EL1 register requires a context synchronization event to ensure that indirect reads made by subsequent instructions (e.g. AUTIASP, PACIASP) observe the new value. When we initialize the boot task's APIAKey in boot_init_stack_canary() via ptrauth_keys_switch_kernel() we miss the necessary ISB, and so there is a window where instructions are not guaranteed to use the new APIAKey value. This has been observed to result in boot-time crashes where PACIASP and AUTIASP within a function used a mixture of the old and new key values. Fix this by having ptrauth_keys_switch_kernel() synchronize the new key value with an ISB. At the same time, __ptrauth_key_install() is renamed to __ptrauth_key_install_nosync() so that it is obvious that this performs no synchronization itself. Fixes: 28321582334c261c ("arm64: initialize ptrauth keys for kernel booting task") Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reported-by: Will Deacon <will@kernel.org> Cc: Amit Daniel Kachhap <amit.kachhap@arm.com> Cc: Marc Zyngier <maz@kernel.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Tested-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/include/asm/pointer_auth.h9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 70c47156e54b..c6b4f0603024 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -47,7 +47,7 @@ static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
get_random_bytes(&keys->apga, sizeof(keys->apga));
}
-#define __ptrauth_key_install(k, v) \
+#define __ptrauth_key_install_nosync(k, v) \
do { \
struct ptrauth_key __pki_v = (v); \
write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1); \
@@ -62,8 +62,11 @@ static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel
static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
{
- if (system_supports_address_auth())
- __ptrauth_key_install(APIA, keys->apia);
+ if (!system_supports_address_auth())
+ return;
+
+ __ptrauth_key_install_nosync(APIA, keys->apia);
+ isb();
}
extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);