arch/arm64/kernel/pointer_auth.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/compat.h>
   4 #include <linux/errno.h>
   5 #include <linux/prctl.h>
   6 #include <linux/random.h>
   7 #include <linux/sched.h>
   8 #include <asm/cpufeature.h>
   9 #include <asm/pointer_auth.h>
  10
  11 int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
  12 {
  13         struct ptrauth_keys_user *keys = &tsk->thread.keys_user;
  14         unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
  15                                       PR_PAC_APDAKEY | PR_PAC_APDBKEY;
  16         unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;
  17
  18         if (!system_supports_address_auth() && !system_supports_generic_auth())
  19                 return -EINVAL;
  20
  21         if (is_compat_thread(task_thread_info(tsk)))
  22                 return -EINVAL;
  23
  24         if (!arg) {
  25                 ptrauth_keys_init_user(keys);
  26                 return 0;
  27         }
  28
  29         if (arg & ~key_mask)
  30                 return -EINVAL;
  31
  32         if (((arg & addr_key_mask) && !system_supports_address_auth()) ||
  33             ((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth()))
  34                 return -EINVAL;
  35
  36         if (arg & PR_PAC_APIAKEY)
  37                 get_random_bytes(&keys->apia, sizeof(keys->apia));
  38         if (arg & PR_PAC_APIBKEY)
  39                 get_random_bytes(&keys->apib, sizeof(keys->apib));
  40         if (arg & PR_PAC_APDAKEY)
  41                 get_random_bytes(&keys->apda, sizeof(keys->apda));
  42         if (arg & PR_PAC_APDBKEY)
  43                 get_random_bytes(&keys->apdb, sizeof(keys->apdb));
  44         if (arg & PR_PAC_APGAKEY)
  45                 get_random_bytes(&keys->apga, sizeof(keys->apga));
  46         ptrauth_keys_install_user(keys);
  47
  48         return 0;
  49 }
  50
  51 static u64 arg_to_enxx_mask(unsigned long arg)
  52 {
  53         u64 sctlr_enxx_mask = 0;
  54
  55         WARN_ON(arg & ~PR_PAC_ENABLED_KEYS_MASK);
  56         if (arg & PR_PAC_APIAKEY)
  57                 sctlr_enxx_mask |= SCTLR_ELx_ENIA;
  58         if (arg & PR_PAC_APIBKEY)
  59                 sctlr_enxx_mask |= SCTLR_ELx_ENIB;
  60         if (arg & PR_PAC_APDAKEY)
  61                 sctlr_enxx_mask |= SCTLR_ELx_ENDA;
  62         if (arg & PR_PAC_APDBKEY)
  63                 sctlr_enxx_mask |= SCTLR_ELx_ENDB;
  64         return sctlr_enxx_mask;
  65 }
  66
  67 int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys,
  68                              unsigned long enabled)
  69 {
  70         u64 sctlr;
  71
  72         if (!system_supports_address_auth())
  73                 return -EINVAL;
  74
  75         if (is_compat_thread(task_thread_info(tsk)))
  76                 return -EINVAL;
  77
  78         if ((keys & ~PR_PAC_ENABLED_KEYS_MASK) || (enabled & ~keys))
  79                 return -EINVAL;
  80
  81         preempt_disable();
  82         sctlr = tsk->thread.sctlr_user;
  83         sctlr &= ~arg_to_enxx_mask(keys);
  84         sctlr |= arg_to_enxx_mask(enabled);
  85         tsk->thread.sctlr_user = sctlr;
  86         if (tsk == current)
  87                 update_sctlr_el1(sctlr);
  88         preempt_enable();
  89
  90         return 0;
  91 }
  92
  93 int ptrauth_get_enabled_keys(struct task_struct *tsk)
  94 {
  95         int retval = 0;
  96
  97         if (!system_supports_address_auth())
  98                 return -EINVAL;
  99
 100         if (is_compat_thread(task_thread_info(tsk)))
 101                 return -EINVAL;
 102
 103         if (tsk->thread.sctlr_user & SCTLR_ELx_ENIA)
 104                 retval |= PR_PAC_APIAKEY;
 105         if (tsk->thread.sctlr_user & SCTLR_ELx_ENIB)
 106                 retval |= PR_PAC_APIBKEY;
 107         if (tsk->thread.sctlr_user & SCTLR_ELx_ENDA)
 108                 retval |= PR_PAC_APDAKEY;
 109         if (tsk->thread.sctlr_user & SCTLR_ELx_ENDB)
 110                 retval |= PR_PAC_APDBKEY;
 111
 112         return retval;
 113 }