arm64/kernel/pointer_auth.c

0001 // SPDX-License-Identifier: GPL-2.0
0002
0003 #include <linux/compat.h>
0004 #include <linux/errno.h>
0005 #include <linux/prctl.h>
0006 #include <linux/random.h>
0007 #include <linux/sched.h>
0008 #include <asm/cpufeature.h>
0009 #include <asm/pointer_auth.h>
0010
0011 int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
0012 {
0013     struct ptrauth_keys_user *keys = &tsk->thread.keys_user;
0014     unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
0015                       PR_PAC_APDAKEY | PR_PAC_APDBKEY;
0016     unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;
0017
0018     if (!system_supports_address_auth() && !system_supports_generic_auth())
0019         return -EINVAL;
0020
0021     if (is_compat_thread(task_thread_info(tsk)))
0022         return -EINVAL;
0023
0024     if (!arg) {
0025         ptrauth_keys_init_user(keys);
0026         return 0;
0027     }
0028
0029     if (arg & ~key_mask)
0030         return -EINVAL;
0031
0032     if (((arg & addr_key_mask) && !system_supports_address_auth()) ||
0033         ((arg & PR_PAC_APGAKEY) && !system_supports_generic_auth()))
0034         return -EINVAL;
0035
0036     if (arg & PR_PAC_APIAKEY)
0037         get_random_bytes(&keys->apia, sizeof(keys->apia));
0038     if (arg & PR_PAC_APIBKEY)
0039         get_random_bytes(&keys->apib, sizeof(keys->apib));
0040     if (arg & PR_PAC_APDAKEY)
0041         get_random_bytes(&keys->apda, sizeof(keys->apda));
0042     if (arg & PR_PAC_APDBKEY)
0043         get_random_bytes(&keys->apdb, sizeof(keys->apdb));
0044     if (arg & PR_PAC_APGAKEY)
0045         get_random_bytes(&keys->apga, sizeof(keys->apga));
0046     ptrauth_keys_install_user(keys);
0047
0048     return 0;
0049 }
0050
0051 static u64 arg_to_enxx_mask(unsigned long arg)
0052 {
0053     u64 sctlr_enxx_mask = 0;
0054
0055     WARN_ON(arg & ~PR_PAC_ENABLED_KEYS_MASK);
0056     if (arg & PR_PAC_APIAKEY)
0057         sctlr_enxx_mask |= SCTLR_ELx_ENIA;
0058     if (arg & PR_PAC_APIBKEY)
0059         sctlr_enxx_mask |= SCTLR_ELx_ENIB;
0060     if (arg & PR_PAC_APDAKEY)
0061         sctlr_enxx_mask |= SCTLR_ELx_ENDA;
0062     if (arg & PR_PAC_APDBKEY)
0063         sctlr_enxx_mask |= SCTLR_ELx_ENDB;
0064     return sctlr_enxx_mask;
0065 }
0066
0067 int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys,
0068                  unsigned long enabled)
0069 {
0070     u64 sctlr;
0071
0072     if (!system_supports_address_auth())
0073         return -EINVAL;
0074
0075     if (is_compat_thread(task_thread_info(tsk)))
0076         return -EINVAL;
0077
0078     if ((keys & ~PR_PAC_ENABLED_KEYS_MASK) || (enabled & ~keys))
0079         return -EINVAL;
0080
0081     preempt_disable();
0082     sctlr = tsk->thread.sctlr_user;
0083     sctlr &= ~arg_to_enxx_mask(keys);
0084     sctlr |= arg_to_enxx_mask(enabled);
0085     tsk->thread.sctlr_user = sctlr;
0086     if (tsk == current)
0087         update_sctlr_el1(sctlr);
0088     preempt_enable();
0089
0090     return 0;
0091 }
0092
0093 int ptrauth_get_enabled_keys(struct task_struct *tsk)
0094 {
0095     int retval = 0;
0096
0097     if (!system_supports_address_auth())
0098         return -EINVAL;
0099
0100     if (is_compat_thread(task_thread_info(tsk)))
0101         return -EINVAL;
0102
0103     if (tsk->thread.sctlr_user & SCTLR_ELx_ENIA)
0104         retval |= PR_PAC_APIAKEY;
0105     if (tsk->thread.sctlr_user & SCTLR_ELx_ENIB)
0106         retval |= PR_PAC_APIBKEY;
0107     if (tsk->thread.sctlr_user & SCTLR_ELx_ENDA)
0108         retval |= PR_PAC_APDAKEY;
0109     if (tsk->thread.sctlr_user & SCTLR_ELx_ENDB)
0110         retval |= PR_PAC_APDBKEY;
0111
0112     return retval;
0113 }