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352 lines
8.3 KiB
352 lines
8.3 KiB
/*
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* Creating audit events from TTY input.
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*
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* Copyright (C) 2007 Red Hat, Inc. All rights reserved. This copyrighted
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* material is made available to anyone wishing to use, modify, copy, or
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* redistribute it subject to the terms and conditions of the GNU General
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* Public License v.2.
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*
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* Authors: Miloslav Trmac <mitr@redhat.com>
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*/
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#include <linux/audit.h>
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#include <linux/file.h>
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#include <linux/tty.h>
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struct tty_audit_buf {
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atomic_t count;
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struct mutex mutex; /* Protects all data below */
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int major, minor; /* The TTY which the data is from */
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unsigned icanon:1;
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size_t valid;
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unsigned char *data; /* Allocated size N_TTY_BUF_SIZE */
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};
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static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
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int icanon)
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{
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struct tty_audit_buf *buf;
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buf = kmalloc(sizeof(*buf), GFP_KERNEL);
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if (!buf)
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goto err;
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if (PAGE_SIZE != N_TTY_BUF_SIZE)
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buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
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else
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buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
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if (!buf->data)
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goto err_buf;
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atomic_set(&buf->count, 1);
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mutex_init(&buf->mutex);
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buf->major = major;
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buf->minor = minor;
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buf->icanon = icanon;
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buf->valid = 0;
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return buf;
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err_buf:
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kfree(buf);
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err:
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return NULL;
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}
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static void tty_audit_buf_free(struct tty_audit_buf *buf)
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{
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WARN_ON(buf->valid != 0);
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if (PAGE_SIZE != N_TTY_BUF_SIZE)
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kfree(buf->data);
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else
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free_page((unsigned long)buf->data);
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kfree(buf);
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}
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static void tty_audit_buf_put(struct tty_audit_buf *buf)
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{
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if (atomic_dec_and_test(&buf->count))
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tty_audit_buf_free(buf);
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}
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/**
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* tty_audit_buf_push - Push buffered data out
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*
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* Generate an audit message from the contents of @buf, which is owned by
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* @tsk with @loginuid. @buf->mutex must be locked.
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*/
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static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
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unsigned int sessionid,
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struct tty_audit_buf *buf)
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{
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struct audit_buffer *ab;
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if (buf->valid == 0)
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return;
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if (audit_enabled == 0)
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return;
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ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
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if (ab) {
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char name[sizeof(tsk->comm)];
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audit_log_format(ab, "tty pid=%u uid=%u auid=%u ses=%u "
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"major=%d minor=%d comm=", tsk->pid, tsk->uid,
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loginuid, sessionid, buf->major, buf->minor);
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get_task_comm(name, tsk);
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audit_log_untrustedstring(ab, name);
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audit_log_format(ab, " data=");
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audit_log_n_untrustedstring(ab, buf->valid, buf->data);
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audit_log_end(ab);
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}
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buf->valid = 0;
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}
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/**
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* tty_audit_buf_push_current - Push buffered data out
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*
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* Generate an audit message from the contents of @buf, which is owned by
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* the current task. @buf->mutex must be locked.
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*/
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static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
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{
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uid_t auid = audit_get_loginuid(current);
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unsigned int sessionid = audit_get_sessionid(current);
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tty_audit_buf_push(current, auid, sessionid, buf);
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}
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/**
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* tty_audit_exit - Handle a task exit
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*
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* Make sure all buffered data is written out and deallocate the buffer.
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* Only needs to be called if current->signal->tty_audit_buf != %NULL.
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*/
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void tty_audit_exit(void)
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{
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struct tty_audit_buf *buf;
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spin_lock_irq(¤t->sighand->siglock);
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buf = current->signal->tty_audit_buf;
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current->signal->tty_audit_buf = NULL;
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spin_unlock_irq(¤t->sighand->siglock);
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if (!buf)
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return;
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mutex_lock(&buf->mutex);
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tty_audit_buf_push_current(buf);
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mutex_unlock(&buf->mutex);
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tty_audit_buf_put(buf);
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}
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/**
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* tty_audit_fork - Copy TTY audit state for a new task
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*
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* Set up TTY audit state in @sig from current. @sig needs no locking.
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*/
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void tty_audit_fork(struct signal_struct *sig)
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{
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spin_lock_irq(¤t->sighand->siglock);
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sig->audit_tty = current->signal->audit_tty;
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spin_unlock_irq(¤t->sighand->siglock);
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sig->tty_audit_buf = NULL;
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}
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/**
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* tty_audit_push_task - Flush task's pending audit data
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*/
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void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid)
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{
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struct tty_audit_buf *buf;
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/* FIXME I think this is correct. Check against netlink once that is
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* I really need to read this code more closely. But that's for
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* another patch.
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*/
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unsigned int sessionid = audit_get_sessionid(tsk);
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spin_lock_irq(&tsk->sighand->siglock);
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buf = tsk->signal->tty_audit_buf;
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if (buf)
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atomic_inc(&buf->count);
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spin_unlock_irq(&tsk->sighand->siglock);
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if (!buf)
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return;
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mutex_lock(&buf->mutex);
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tty_audit_buf_push(tsk, loginuid, sessionid, buf);
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mutex_unlock(&buf->mutex);
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tty_audit_buf_put(buf);
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}
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/**
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* tty_audit_buf_get - Get an audit buffer.
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*
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* Get an audit buffer for @tty, allocate it if necessary. Return %NULL
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* if TTY auditing is disabled or out of memory. Otherwise, return a new
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* reference to the buffer.
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*/
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static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
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{
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struct tty_audit_buf *buf, *buf2;
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buf = NULL;
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buf2 = NULL;
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spin_lock_irq(¤t->sighand->siglock);
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if (likely(!current->signal->audit_tty))
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goto out;
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buf = current->signal->tty_audit_buf;
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if (buf) {
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atomic_inc(&buf->count);
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goto out;
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}
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spin_unlock_irq(¤t->sighand->siglock);
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buf2 = tty_audit_buf_alloc(tty->driver->major,
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tty->driver->minor_start + tty->index,
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tty->icanon);
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if (buf2 == NULL) {
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audit_log_lost("out of memory in TTY auditing");
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return NULL;
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}
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spin_lock_irq(¤t->sighand->siglock);
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if (!current->signal->audit_tty)
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goto out;
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buf = current->signal->tty_audit_buf;
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if (!buf) {
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current->signal->tty_audit_buf = buf2;
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buf = buf2;
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buf2 = NULL;
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}
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atomic_inc(&buf->count);
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/* Fall through */
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out:
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spin_unlock_irq(¤t->sighand->siglock);
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if (buf2)
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tty_audit_buf_free(buf2);
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return buf;
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}
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/**
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* tty_audit_add_data - Add data for TTY auditing.
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*
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* Audit @data of @size from @tty, if necessary.
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*/
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void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
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size_t size)
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{
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struct tty_audit_buf *buf;
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int major, minor;
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if (unlikely(size == 0))
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return;
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buf = tty_audit_buf_get(tty);
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if (!buf)
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return;
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mutex_lock(&buf->mutex);
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major = tty->driver->major;
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minor = tty->driver->minor_start + tty->index;
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if (buf->major != major || buf->minor != minor
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|| buf->icanon != tty->icanon) {
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tty_audit_buf_push_current(buf);
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buf->major = major;
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buf->minor = minor;
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buf->icanon = tty->icanon;
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}
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do {
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size_t run;
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run = N_TTY_BUF_SIZE - buf->valid;
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if (run > size)
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run = size;
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memcpy(buf->data + buf->valid, data, run);
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buf->valid += run;
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data += run;
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size -= run;
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if (buf->valid == N_TTY_BUF_SIZE)
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tty_audit_buf_push_current(buf);
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} while (size != 0);
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mutex_unlock(&buf->mutex);
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tty_audit_buf_put(buf);
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}
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/**
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* tty_audit_push - Push buffered data out
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*
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* Make sure no audit data is pending for @tty on the current process.
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*/
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void tty_audit_push(struct tty_struct *tty)
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{
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struct tty_audit_buf *buf;
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spin_lock_irq(¤t->sighand->siglock);
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if (likely(!current->signal->audit_tty)) {
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spin_unlock_irq(¤t->sighand->siglock);
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return;
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}
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buf = current->signal->tty_audit_buf;
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if (buf)
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atomic_inc(&buf->count);
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spin_unlock_irq(¤t->sighand->siglock);
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if (buf) {
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int major, minor;
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major = tty->driver->major;
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minor = tty->driver->minor_start + tty->index;
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mutex_lock(&buf->mutex);
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if (buf->major == major && buf->minor == minor)
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tty_audit_buf_push_current(buf);
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mutex_unlock(&buf->mutex);
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tty_audit_buf_put(buf);
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}
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}
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/**
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* tty_audit_opening - A TTY is being opened.
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*
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* As a special hack, tasks that close all their TTYs and open new ones
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* are assumed to be system daemons (e.g. getty) and auditing is
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* automatically disabled for them.
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*/
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void tty_audit_opening(void)
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{
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int disable;
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disable = 1;
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spin_lock_irq(¤t->sighand->siglock);
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if (current->signal->audit_tty == 0)
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disable = 0;
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spin_unlock_irq(¤t->sighand->siglock);
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if (!disable)
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return;
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task_lock(current);
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if (current->files) {
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struct fdtable *fdt;
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unsigned i;
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/*
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* We don't take a ref to the file, so we must hold ->file_lock
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* instead.
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*/
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spin_lock(¤t->files->file_lock);
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fdt = files_fdtable(current->files);
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for (i = 0; i < fdt->max_fds; i++) {
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struct file *filp;
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filp = fcheck_files(current->files, i);
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if (filp && is_tty(filp)) {
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disable = 0;
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break;
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}
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}
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spin_unlock(¤t->files->file_lock);
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}
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task_unlock(current);
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if (!disable)
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return;
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spin_lock_irq(¤t->sighand->siglock);
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current->signal->audit_tty = 0;
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spin_unlock_irq(¤t->sighand->siglock);
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}
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