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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 | // SPDX-License-Identifier: GPL-2.0-only /* * mmap based event notifications for SELinux * * Author: KaiGai Kohei <kaigai@ak.jp.nec.com> * * Copyright (C) 2010 NEC corporation */ #include <linux/kernel.h> #include <linux/gfp.h> #include <linux/mm.h> #include <linux/mutex.h> #include "avc.h" #include "services.h" /* * The selinux_status_page shall be exposed to userspace applications * using mmap interface on /selinux/status. * It enables to notify applications a few events that will cause reset * of userspace access vector without context switching. * * The selinux_kernel_status structure on the head of status page is * protected from concurrent accesses using seqlock logic, so userspace * application should reference the status page according to the seqlock * logic. * * Typically, application checks status->sequence at the head of access * control routine. If it is odd-number, kernel is updating the status, * so please wait for a moment. If it is changed from the last sequence * number, it means something happen, so application will reset userspace * avc, if needed. * In most cases, application shall confirm the kernel status is not * changed without any system call invocations. */ /* * selinux_kernel_status_page * * It returns a reference to selinux_status_page. If the status page is * not allocated yet, it also tries to allocate it at the first time. */ struct page *selinux_kernel_status_page(struct selinux_state *state) { struct selinux_kernel_status *status; struct page *result = NULL; mutex_lock(&state->ss->status_lock); if (!state->ss->status_page) { state->ss->status_page = alloc_page(GFP_KERNEL|__GFP_ZERO); if (state->ss->status_page) { status = page_address(state->ss->status_page); status->version = SELINUX_KERNEL_STATUS_VERSION; status->sequence = 0; status->enforcing = enforcing_enabled(state); /* * NOTE: the next policyload event shall set * a positive value on the status->policyload, * although it may not be 1, but never zero. * So, application can know it was updated. */ status->policyload = 0; status->deny_unknown = !security_get_allow_unknown(state); } } result = state->ss->status_page; mutex_unlock(&state->ss->status_lock); return result; } /* * selinux_status_update_setenforce * * It updates status of the current enforcing/permissive mode. */ void selinux_status_update_setenforce(struct selinux_state *state, int enforcing) { struct selinux_kernel_status *status; mutex_lock(&state->ss->status_lock); if (state->ss->status_page) { status = page_address(state->ss->status_page); status->sequence++; smp_wmb(); status->enforcing = enforcing; smp_wmb(); status->sequence++; } mutex_unlock(&state->ss->status_lock); } /* * selinux_status_update_policyload * * It updates status of the times of policy reloaded, and current * setting of deny_unknown. */ void selinux_status_update_policyload(struct selinux_state *state, int seqno) { struct selinux_kernel_status *status; mutex_lock(&state->ss->status_lock); if (state->ss->status_page) { status = page_address(state->ss->status_page); status->sequence++; smp_wmb(); status->policyload = seqno; status->deny_unknown = !security_get_allow_unknown(state); smp_wmb(); status->sequence++; } mutex_unlock(&state->ss->status_lock); } |