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| author | Mark Rutland <mark.rutland@arm.com> | 2020-04-21 15:10:14 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-04-21 17:52:56 +0300 |
| commit | 3fabb43818c9bfe7c4084badfa21d4e8187021a6 (patch) | |
| tree | 6e72ca8a70648b08c5b03fb984374e406701ad37 /arch/arm64 | |
| parent | ae83d0b416db002fe95601e7f97f64b59514d936 (diff) | |
| download | linux-3fabb43818c9bfe7c4084badfa21d4e8187021a6.tar.xz | |
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/arm64')
| -rw-r--r-- | arch/arm64/include/asm/pointer_auth.h | 9 |
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); |