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124 lines
3.3 KiB
124 lines
3.3 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* mmap based event notifications for SELinux |
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* |
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* Author: KaiGai Kohei <[email protected]> |
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* |
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* Copyright (C) 2010 NEC corporation |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/gfp.h> |
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#include <linux/mm.h> |
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#include <linux/mutex.h> |
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#include "avc.h" |
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#include "security.h" |
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/* |
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* The selinux_status_page shall be exposed to userspace applications |
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* using mmap interface on /selinux/status. |
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* It enables to notify applications a few events that will cause reset |
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* of userspace access vector without context switching. |
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* |
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* The selinux_kernel_status structure on the head of status page is |
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* protected from concurrent accesses using seqlock logic, so userspace |
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* application should reference the status page according to the seqlock |
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* logic. |
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* |
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* Typically, application checks status->sequence at the head of access |
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* control routine. If it is odd-number, kernel is updating the status, |
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* so please wait for a moment. If it is changed from the last sequence |
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* number, it means something happen, so application will reset userspace |
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* avc, if needed. |
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* In most cases, application shall confirm the kernel status is not |
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* changed without any system call invocations. |
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*/ |
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/* |
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* selinux_kernel_status_page |
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* |
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* It returns a reference to selinux_status_page. If the status page is |
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* not allocated yet, it also tries to allocate it at the first time. |
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*/ |
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struct page *selinux_kernel_status_page(struct selinux_state *state) |
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{ |
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struct selinux_kernel_status *status; |
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struct page *result = NULL; |
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mutex_lock(&state->status_lock); |
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if (!state->status_page) { |
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state->status_page = alloc_page(GFP_KERNEL|__GFP_ZERO); |
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if (state->status_page) { |
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status = page_address(state->status_page); |
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status->version = SELINUX_KERNEL_STATUS_VERSION; |
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status->sequence = 0; |
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status->enforcing = enforcing_enabled(state); |
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/* |
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* NOTE: the next policyload event shall set |
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* a positive value on the status->policyload, |
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* although it may not be 1, but never zero. |
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* So, application can know it was updated. |
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*/ |
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status->policyload = 0; |
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status->deny_unknown = |
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!security_get_allow_unknown(state); |
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} |
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} |
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result = state->status_page; |
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mutex_unlock(&state->status_lock); |
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return result; |
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} |
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/* |
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* selinux_status_update_setenforce |
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* |
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* It updates status of the current enforcing/permissive mode. |
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*/ |
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void selinux_status_update_setenforce(struct selinux_state *state, |
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int enforcing) |
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{ |
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struct selinux_kernel_status *status; |
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mutex_lock(&state->status_lock); |
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if (state->status_page) { |
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status = page_address(state->status_page); |
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status->sequence++; |
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smp_wmb(); |
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status->enforcing = enforcing; |
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smp_wmb(); |
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status->sequence++; |
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} |
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mutex_unlock(&state->status_lock); |
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} |
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/* |
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* selinux_status_update_policyload |
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* |
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* It updates status of the times of policy reloaded, and current |
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* setting of deny_unknown. |
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*/ |
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void selinux_status_update_policyload(struct selinux_state *state, |
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int seqno) |
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{ |
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struct selinux_kernel_status *status; |
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mutex_lock(&state->status_lock); |
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if (state->status_page) { |
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status = page_address(state->status_page); |
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status->sequence++; |
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smp_wmb(); |
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status->policyload = seqno; |
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status->deny_unknown = !security_get_allow_unknown(state); |
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smp_wmb(); |
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status->sequence++; |
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} |
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mutex_unlock(&state->status_lock); |
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}
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