mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-21 19:53:59 +08:00
454e3126cb
This changes kcmp_epoll_target to use the new exec_update_mutex instead of cred_guard_mutex. This should be safe, as the credentials are only used for reading, and furthermore ->mm and ->sighand are updated on execve, but only under the new exec_update_mutex. Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
257 lines
5.7 KiB
C
257 lines
5.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/kernel.h>
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#include <linux/syscalls.h>
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#include <linux/fdtable.h>
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#include <linux/string.h>
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#include <linux/random.h>
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#include <linux/module.h>
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#include <linux/ptrace.h>
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#include <linux/init.h>
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#include <linux/errno.h>
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#include <linux/cache.h>
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#include <linux/bug.h>
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#include <linux/err.h>
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#include <linux/kcmp.h>
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#include <linux/capability.h>
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#include <linux/list.h>
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#include <linux/eventpoll.h>
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#include <linux/file.h>
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#include <asm/unistd.h>
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/*
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* We don't expose the real in-memory order of objects for security reasons.
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* But still the comparison results should be suitable for sorting. So we
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* obfuscate kernel pointers values and compare the production instead.
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*
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* The obfuscation is done in two steps. First we xor the kernel pointer with
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* a random value, which puts pointer into a new position in a reordered space.
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* Secondly we multiply the xor production with a large odd random number to
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* permute its bits even more (the odd multiplier guarantees that the product
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* is unique ever after the high bits are truncated, since any odd number is
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* relative prime to 2^n).
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*
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* Note also that the obfuscation itself is invisible to userspace and if needed
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* it can be changed to an alternate scheme.
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*/
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static unsigned long cookies[KCMP_TYPES][2] __read_mostly;
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static long kptr_obfuscate(long v, int type)
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{
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return (v ^ cookies[type][0]) * cookies[type][1];
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}
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/*
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* 0 - equal, i.e. v1 = v2
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* 1 - less than, i.e. v1 < v2
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* 2 - greater than, i.e. v1 > v2
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* 3 - not equal but ordering unavailable (reserved for future)
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*/
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static int kcmp_ptr(void *v1, void *v2, enum kcmp_type type)
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{
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long t1, t2;
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t1 = kptr_obfuscate((long)v1, type);
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t2 = kptr_obfuscate((long)v2, type);
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return (t1 < t2) | ((t1 > t2) << 1);
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}
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/* The caller must have pinned the task */
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static struct file *
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get_file_raw_ptr(struct task_struct *task, unsigned int idx)
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{
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struct file *file = NULL;
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task_lock(task);
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rcu_read_lock();
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if (task->files)
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file = fcheck_files(task->files, idx);
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rcu_read_unlock();
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task_unlock(task);
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return file;
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}
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static void kcmp_unlock(struct mutex *m1, struct mutex *m2)
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{
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if (likely(m2 != m1))
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mutex_unlock(m2);
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mutex_unlock(m1);
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}
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static int kcmp_lock(struct mutex *m1, struct mutex *m2)
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{
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int err;
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if (m2 > m1)
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swap(m1, m2);
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err = mutex_lock_killable(m1);
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if (!err && likely(m1 != m2)) {
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err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);
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if (err)
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mutex_unlock(m1);
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}
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return err;
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}
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#ifdef CONFIG_EPOLL
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static int kcmp_epoll_target(struct task_struct *task1,
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struct task_struct *task2,
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unsigned long idx1,
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struct kcmp_epoll_slot __user *uslot)
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{
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struct file *filp, *filp_epoll, *filp_tgt;
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struct kcmp_epoll_slot slot;
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struct files_struct *files;
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if (copy_from_user(&slot, uslot, sizeof(slot)))
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return -EFAULT;
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filp = get_file_raw_ptr(task1, idx1);
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if (!filp)
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return -EBADF;
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files = get_files_struct(task2);
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if (!files)
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return -EBADF;
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spin_lock(&files->file_lock);
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filp_epoll = fcheck_files(files, slot.efd);
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if (filp_epoll)
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get_file(filp_epoll);
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else
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filp_tgt = ERR_PTR(-EBADF);
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spin_unlock(&files->file_lock);
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put_files_struct(files);
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if (filp_epoll) {
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filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff);
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fput(filp_epoll);
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}
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if (IS_ERR(filp_tgt))
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return PTR_ERR(filp_tgt);
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return kcmp_ptr(filp, filp_tgt, KCMP_FILE);
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}
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#else
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static int kcmp_epoll_target(struct task_struct *task1,
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struct task_struct *task2,
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unsigned long idx1,
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struct kcmp_epoll_slot __user *uslot)
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{
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return -EOPNOTSUPP;
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}
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#endif
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SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
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unsigned long, idx1, unsigned long, idx2)
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{
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struct task_struct *task1, *task2;
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int ret;
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rcu_read_lock();
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/*
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* Tasks are looked up in caller's PID namespace only.
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*/
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task1 = find_task_by_vpid(pid1);
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task2 = find_task_by_vpid(pid2);
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if (!task1 || !task2)
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goto err_no_task;
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get_task_struct(task1);
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get_task_struct(task2);
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rcu_read_unlock();
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/*
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* One should have enough rights to inspect task details.
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*/
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ret = kcmp_lock(&task1->signal->exec_update_mutex,
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&task2->signal->exec_update_mutex);
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if (ret)
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goto err;
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if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
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!ptrace_may_access(task2, PTRACE_MODE_READ_REALCREDS)) {
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ret = -EPERM;
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goto err_unlock;
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}
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switch (type) {
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case KCMP_FILE: {
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struct file *filp1, *filp2;
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filp1 = get_file_raw_ptr(task1, idx1);
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filp2 = get_file_raw_ptr(task2, idx2);
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if (filp1 && filp2)
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ret = kcmp_ptr(filp1, filp2, KCMP_FILE);
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else
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ret = -EBADF;
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break;
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}
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case KCMP_VM:
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ret = kcmp_ptr(task1->mm, task2->mm, KCMP_VM);
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break;
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case KCMP_FILES:
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ret = kcmp_ptr(task1->files, task2->files, KCMP_FILES);
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break;
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case KCMP_FS:
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ret = kcmp_ptr(task1->fs, task2->fs, KCMP_FS);
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break;
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case KCMP_SIGHAND:
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ret = kcmp_ptr(task1->sighand, task2->sighand, KCMP_SIGHAND);
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break;
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case KCMP_IO:
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ret = kcmp_ptr(task1->io_context, task2->io_context, KCMP_IO);
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break;
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case KCMP_SYSVSEM:
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#ifdef CONFIG_SYSVIPC
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ret = kcmp_ptr(task1->sysvsem.undo_list,
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task2->sysvsem.undo_list,
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KCMP_SYSVSEM);
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#else
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ret = -EOPNOTSUPP;
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#endif
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break;
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case KCMP_EPOLL_TFD:
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ret = kcmp_epoll_target(task1, task2, idx1, (void *)idx2);
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break;
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default:
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ret = -EINVAL;
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break;
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}
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err_unlock:
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kcmp_unlock(&task1->signal->exec_update_mutex,
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&task2->signal->exec_update_mutex);
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err:
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put_task_struct(task1);
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put_task_struct(task2);
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return ret;
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err_no_task:
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rcu_read_unlock();
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return -ESRCH;
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}
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static __init int kcmp_cookies_init(void)
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{
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int i;
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get_random_bytes(cookies, sizeof(cookies));
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for (i = 0; i < KCMP_TYPES; i++)
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cookies[i][1] |= (~(~0UL >> 1) | 1);
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return 0;
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}
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arch_initcall(kcmp_cookies_init);
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