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d2e0d8f974
In the next patch, we will start reading sctlr_user from mte_update_sctlr_user and subsequently writing a new value based on the task's TCF setting and potentially the per-CPU TCF preference. This means that we need to be careful to disable preemption around any code sequences that read from sctlr_user and subsequently write to sctlr_user and/or SCTLR_EL1, so that we don't end up writing a stale value (based on the previous CPU's TCF preference) to either of them. We currently have four such sequences, in the prctl handlers for PR_SET_TAGGED_ADDR_CTRL and PR_PAC_SET_ENABLED_KEYS, as well as in the task initialization code that resets the prctl settings. Change the prctl handlers to disable preemption in the handlers themselves rather than the functions that they call, and change the task initialization code to call the respective prctl handlers instead of setting sctlr_user directly. As a result of this change, we no longer need the helper function set_task_sctlr_el1, nor does its behavior make sense any more, so remove it. Signed-off-by: Peter Collingbourne <pcc@google.com> Link: https://linux-review.googlesource.com/id/Ic0e8a0c00bb47d786c1e8011df0b7fe99bee4bb5 Link: https://lore.kernel.org/r/20210727205300.2554659-4-pcc@google.com Acked-by: Will Deacon <will@kernel.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
113 lines
2.8 KiB
C
113 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/compat.h>
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#include <linux/errno.h>
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#include <linux/prctl.h>
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#include <linux/random.h>
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#include <linux/sched.h>
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#include <asm/cpufeature.h>
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#include <asm/pointer_auth.h>
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int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
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{
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struct ptrauth_keys_user *keys = &tsk->thread.keys_user;
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unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
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PR_PAC_APDAKEY | PR_PAC_APDBKEY;
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unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;
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if (!system_supports_address_auth() && !system_supports_generic_auth())
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return -EINVAL;
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if (is_compat_thread(task_thread_info(tsk)))
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return -EINVAL;
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if (!arg) {
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ptrauth_keys_init_user(keys);
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return 0;
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}
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if (arg & ~key_mask)
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return -EINVAL;
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if (((arg & addr_key_mask) && !system_supports_address_auth()) ||
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((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth()))
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return -EINVAL;
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if (arg & PR_PAC_APIAKEY)
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get_random_bytes(&keys->apia, sizeof(keys->apia));
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if (arg & PR_PAC_APIBKEY)
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get_random_bytes(&keys->apib, sizeof(keys->apib));
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if (arg & PR_PAC_APDAKEY)
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get_random_bytes(&keys->apda, sizeof(keys->apda));
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if (arg & PR_PAC_APDBKEY)
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get_random_bytes(&keys->apdb, sizeof(keys->apdb));
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if (arg & PR_PAC_APGAKEY)
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get_random_bytes(&keys->apga, sizeof(keys->apga));
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ptrauth_keys_install_user(keys);
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return 0;
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}
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static u64 arg_to_enxx_mask(unsigned long arg)
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{
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u64 sctlr_enxx_mask = 0;
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WARN_ON(arg & ~PR_PAC_ENABLED_KEYS_MASK);
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if (arg & PR_PAC_APIAKEY)
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sctlr_enxx_mask |= SCTLR_ELx_ENIA;
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if (arg & PR_PAC_APIBKEY)
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sctlr_enxx_mask |= SCTLR_ELx_ENIB;
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if (arg & PR_PAC_APDAKEY)
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sctlr_enxx_mask |= SCTLR_ELx_ENDA;
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if (arg & PR_PAC_APDBKEY)
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sctlr_enxx_mask |= SCTLR_ELx_ENDB;
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return sctlr_enxx_mask;
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}
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int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys,
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unsigned long enabled)
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{
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u64 sctlr;
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if (!system_supports_address_auth())
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return -EINVAL;
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if (is_compat_thread(task_thread_info(tsk)))
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return -EINVAL;
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if ((keys & ~PR_PAC_ENABLED_KEYS_MASK) || (enabled & ~keys))
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return -EINVAL;
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preempt_disable();
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sctlr = tsk->thread.sctlr_user;
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sctlr &= ~arg_to_enxx_mask(keys);
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sctlr |= arg_to_enxx_mask(enabled);
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tsk->thread.sctlr_user = sctlr;
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if (tsk == current)
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update_sctlr_el1(sctlr);
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preempt_enable();
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return 0;
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}
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int ptrauth_get_enabled_keys(struct task_struct *tsk)
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{
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int retval = 0;
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if (!system_supports_address_auth())
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return -EINVAL;
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if (is_compat_thread(task_thread_info(tsk)))
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return -EINVAL;
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if (tsk->thread.sctlr_user & SCTLR_ELx_ENIA)
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retval |= PR_PAC_APIAKEY;
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if (tsk->thread.sctlr_user & SCTLR_ELx_ENIB)
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retval |= PR_PAC_APIBKEY;
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if (tsk->thread.sctlr_user & SCTLR_ELx_ENDA)
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retval |= PR_PAC_APDAKEY;
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if (tsk->thread.sctlr_user & SCTLR_ELx_ENDB)
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retval |= PR_PAC_APDBKEY;
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return retval;
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}
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