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3fabb43818
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: 2832158233 ("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>
95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __ASM_POINTER_AUTH_H
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#define __ASM_POINTER_AUTH_H
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#include <linux/bitops.h>
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#include <linux/random.h>
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#include <asm/cpufeature.h>
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#include <asm/memory.h>
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#include <asm/sysreg.h>
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#ifdef CONFIG_ARM64_PTR_AUTH
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/*
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* Each key is a 128-bit quantity which is split across a pair of 64-bit
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* registers (Lo and Hi).
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*/
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struct ptrauth_key {
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unsigned long lo, hi;
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};
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/*
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* We give each process its own keys, which are shared by all threads. The keys
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* are inherited upon fork(), and reinitialised upon exec*().
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*/
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struct ptrauth_keys_user {
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struct ptrauth_key apia;
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struct ptrauth_key apib;
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struct ptrauth_key apda;
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struct ptrauth_key apdb;
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struct ptrauth_key apga;
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};
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struct ptrauth_keys_kernel {
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struct ptrauth_key apia;
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};
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static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
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{
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if (system_supports_address_auth()) {
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get_random_bytes(&keys->apia, sizeof(keys->apia));
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get_random_bytes(&keys->apib, sizeof(keys->apib));
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get_random_bytes(&keys->apda, sizeof(keys->apda));
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get_random_bytes(&keys->apdb, sizeof(keys->apdb));
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}
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if (system_supports_generic_auth())
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get_random_bytes(&keys->apga, sizeof(keys->apga));
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}
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#define __ptrauth_key_install_nosync(k, v) \
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do { \
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struct ptrauth_key __pki_v = (v); \
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write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1); \
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write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \
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} while (0)
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static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
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{
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if (system_supports_address_auth())
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get_random_bytes(&keys->apia, sizeof(keys->apia));
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}
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static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
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{
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if (!system_supports_address_auth())
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return;
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__ptrauth_key_install_nosync(APIA, keys->apia);
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isb();
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}
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extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
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static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
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{
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return ptrauth_clear_pac(ptr);
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}
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#define ptrauth_thread_init_user(tsk) \
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ptrauth_keys_init_user(&(tsk)->thread.keys_user)
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#define ptrauth_thread_init_kernel(tsk) \
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ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
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#define ptrauth_thread_switch_kernel(tsk) \
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ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
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#else /* CONFIG_ARM64_PTR_AUTH */
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#define ptrauth_prctl_reset_keys(tsk, arg) (-EINVAL)
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#define ptrauth_strip_insn_pac(lr) (lr)
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#define ptrauth_thread_init_user(tsk)
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#define ptrauth_thread_init_kernel(tsk)
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#define ptrauth_thread_switch_kernel(tsk)
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#endif /* CONFIG_ARM64_PTR_AUTH */
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#endif /* __ASM_POINTER_AUTH_H */
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