380 lines
9.6 KiB
C
380 lines
9.6 KiB
C
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// SPDX-License-Identifier: GPL-2.0-or-later
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#include <linux/compat.h>
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#include <linux/syscalls.h>
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#include <linux/time_namespace.h>
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#include "futex.h"
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/*
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* Support for robust futexes: the kernel cleans up held futexes at
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* thread exit time.
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*
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* Implementation: user-space maintains a per-thread list of locks it
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* is holding. Upon do_exit(), the kernel carefully walks this list,
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* and marks all locks that are owned by this thread with the
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* FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
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* always manipulated with the lock held, so the list is private and
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* per-thread. Userspace also maintains a per-thread 'list_op_pending'
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* field, to allow the kernel to clean up if the thread dies after
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* acquiring the lock, but just before it could have added itself to
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* the list. There can only be one such pending lock.
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*/
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/**
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* sys_set_robust_list() - Set the robust-futex list head of a task
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* @head: pointer to the list-head
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* @len: length of the list-head, as userspace expects
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*/
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SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
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size_t, len)
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{
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/*
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* The kernel knows only one size for now:
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*/
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if (unlikely(len != sizeof(*head)))
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return -EINVAL;
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current->robust_list = head;
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return 0;
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}
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/**
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* sys_get_robust_list() - Get the robust-futex list head of a task
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* @pid: pid of the process [zero for current task]
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* @head_ptr: pointer to a list-head pointer, the kernel fills it in
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* @len_ptr: pointer to a length field, the kernel fills in the header size
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*/
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SYSCALL_DEFINE3(get_robust_list, int, pid,
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struct robust_list_head __user * __user *, head_ptr,
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size_t __user *, len_ptr)
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{
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struct robust_list_head __user *head;
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unsigned long ret;
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struct task_struct *p;
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rcu_read_lock();
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ret = -ESRCH;
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if (!pid)
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p = current;
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else {
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p = find_task_by_vpid(pid);
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if (!p)
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goto err_unlock;
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}
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ret = -EPERM;
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if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
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goto err_unlock;
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head = p->robust_list;
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rcu_read_unlock();
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if (put_user(sizeof(*head), len_ptr))
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return -EFAULT;
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return put_user(head, head_ptr);
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err_unlock:
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rcu_read_unlock();
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return ret;
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}
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long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
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u32 __user *uaddr2, u32 val2, u32 val3)
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{
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int cmd = op & FUTEX_CMD_MASK;
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unsigned int flags = 0;
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if (!(op & FUTEX_PRIVATE_FLAG))
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flags |= FLAGS_SHARED;
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if (op & FUTEX_CLOCK_REALTIME) {
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flags |= FLAGS_CLOCKRT;
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if (cmd != FUTEX_WAIT_BITSET && cmd != FUTEX_WAIT_REQUEUE_PI &&
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cmd != FUTEX_LOCK_PI2)
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return -ENOSYS;
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}
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switch (cmd) {
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case FUTEX_WAIT:
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val3 = FUTEX_BITSET_MATCH_ANY;
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fallthrough;
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case FUTEX_WAIT_BITSET:
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return futex_wait(uaddr, flags, val, timeout, val3);
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case FUTEX_WAKE:
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val3 = FUTEX_BITSET_MATCH_ANY;
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fallthrough;
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case FUTEX_WAKE_BITSET:
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return futex_wake(uaddr, flags, val, val3);
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case FUTEX_REQUEUE:
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return futex_requeue(uaddr, flags, uaddr2, val, val2, NULL, 0);
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case FUTEX_CMP_REQUEUE:
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return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 0);
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case FUTEX_WAKE_OP:
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return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);
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case FUTEX_LOCK_PI:
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flags |= FLAGS_CLOCKRT;
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fallthrough;
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case FUTEX_LOCK_PI2:
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return futex_lock_pi(uaddr, flags, timeout, 0);
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case FUTEX_UNLOCK_PI:
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return futex_unlock_pi(uaddr, flags);
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case FUTEX_TRYLOCK_PI:
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return futex_lock_pi(uaddr, flags, NULL, 1);
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case FUTEX_WAIT_REQUEUE_PI:
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val3 = FUTEX_BITSET_MATCH_ANY;
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return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,
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uaddr2);
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case FUTEX_CMP_REQUEUE_PI:
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return futex_requeue(uaddr, flags, uaddr2, val, val2, &val3, 1);
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}
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return -ENOSYS;
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}
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static __always_inline bool futex_cmd_has_timeout(u32 cmd)
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{
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switch (cmd) {
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case FUTEX_WAIT:
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case FUTEX_LOCK_PI:
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case FUTEX_LOCK_PI2:
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case FUTEX_WAIT_BITSET:
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case FUTEX_WAIT_REQUEUE_PI:
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return true;
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}
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return false;
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}
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static __always_inline int
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futex_init_timeout(u32 cmd, u32 op, struct timespec64 *ts, ktime_t *t)
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{
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if (!timespec64_valid(ts))
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return -EINVAL;
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*t = timespec64_to_ktime(*ts);
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if (cmd == FUTEX_WAIT)
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*t = ktime_add_safe(ktime_get(), *t);
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else if (cmd != FUTEX_LOCK_PI && !(op & FUTEX_CLOCK_REALTIME))
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*t = timens_ktime_to_host(CLOCK_MONOTONIC, *t);
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return 0;
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}
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SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
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const struct __kernel_timespec __user *, utime,
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u32 __user *, uaddr2, u32, val3)
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{
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int ret, cmd = op & FUTEX_CMD_MASK;
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ktime_t t, *tp = NULL;
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struct timespec64 ts;
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if (utime && futex_cmd_has_timeout(cmd)) {
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if (unlikely(should_fail_futex(!(op & FUTEX_PRIVATE_FLAG))))
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return -EFAULT;
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if (get_timespec64(&ts, utime))
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return -EFAULT;
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ret = futex_init_timeout(cmd, op, &ts, &t);
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if (ret)
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return ret;
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tp = &t;
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}
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return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
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}
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/* Mask of available flags for each futex in futex_waitv list */
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#define FUTEXV_WAITER_MASK (FUTEX_32 | FUTEX_PRIVATE_FLAG)
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/**
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* futex_parse_waitv - Parse a waitv array from userspace
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* @futexv: Kernel side list of waiters to be filled
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* @uwaitv: Userspace list to be parsed
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* @nr_futexes: Length of futexv
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*
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* Return: Error code on failure, 0 on success
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*/
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static int futex_parse_waitv(struct futex_vector *futexv,
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struct futex_waitv __user *uwaitv,
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unsigned int nr_futexes)
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{
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struct futex_waitv aux;
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unsigned int i;
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for (i = 0; i < nr_futexes; i++) {
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if (copy_from_user(&aux, &uwaitv[i], sizeof(aux)))
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return -EFAULT;
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if ((aux.flags & ~FUTEXV_WAITER_MASK) || aux.__reserved)
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return -EINVAL;
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if (!(aux.flags & FUTEX_32))
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return -EINVAL;
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futexv[i].w.flags = aux.flags;
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futexv[i].w.val = aux.val;
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futexv[i].w.uaddr = aux.uaddr;
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futexv[i].q = futex_q_init;
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}
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return 0;
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}
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/**
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* sys_futex_waitv - Wait on a list of futexes
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* @waiters: List of futexes to wait on
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* @nr_futexes: Length of futexv
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* @flags: Flag for timeout (monotonic/realtime)
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* @timeout: Optional absolute timeout.
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* @clockid: Clock to be used for the timeout, realtime or monotonic.
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*
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* Given an array of `struct futex_waitv`, wait on each uaddr. The thread wakes
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* if a futex_wake() is performed at any uaddr. The syscall returns immediately
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* if any waiter has *uaddr != val. *timeout is an optional timeout value for
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* the operation. Each waiter has individual flags. The `flags` argument for
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* the syscall should be used solely for specifying the timeout as realtime, if
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* needed. Flags for private futexes, sizes, etc. should be used on the
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* individual flags of each waiter.
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*
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* Returns the array index of one of the woken futexes. No further information
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* is provided: any number of other futexes may also have been woken by the
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* same event, and if more than one futex was woken, the retrned index may
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* refer to any one of them. (It is not necessaryily the futex with the
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* smallest index, nor the one most recently woken, nor...)
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*/
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SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
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unsigned int, nr_futexes, unsigned int, flags,
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struct __kernel_timespec __user *, timeout, clockid_t, clockid)
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{
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struct hrtimer_sleeper to;
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struct futex_vector *futexv;
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struct timespec64 ts;
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ktime_t time;
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int ret;
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/* This syscall supports no flags for now */
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if (flags)
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return -EINVAL;
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if (!nr_futexes || nr_futexes > FUTEX_WAITV_MAX || !waiters)
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return -EINVAL;
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if (timeout) {
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int flag_clkid = 0, flag_init = 0;
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if (clockid == CLOCK_REALTIME) {
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flag_clkid = FLAGS_CLOCKRT;
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flag_init = FUTEX_CLOCK_REALTIME;
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}
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if (clockid != CLOCK_REALTIME && clockid != CLOCK_MONOTONIC)
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return -EINVAL;
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if (get_timespec64(&ts, timeout))
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return -EFAULT;
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/*
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* Since there's no opcode for futex_waitv, use
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* FUTEX_WAIT_BITSET that uses absolute timeout as well
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*/
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ret = futex_init_timeout(FUTEX_WAIT_BITSET, flag_init, &ts, &time);
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if (ret)
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return ret;
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futex_setup_timer(&time, &to, flag_clkid, 0);
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}
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futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
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if (!futexv) {
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ret = -ENOMEM;
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goto destroy_timer;
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}
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ret = futex_parse_waitv(futexv, waiters, nr_futexes);
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if (!ret)
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ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);
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kfree(futexv);
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destroy_timer:
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if (timeout) {
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hrtimer_cancel(&to.timer);
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destroy_hrtimer_on_stack(&to.timer);
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}
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return ret;
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}
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#ifdef CONFIG_COMPAT
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COMPAT_SYSCALL_DEFINE2(set_robust_list,
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struct compat_robust_list_head __user *, head,
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compat_size_t, len)
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{
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if (unlikely(len != sizeof(*head)))
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return -EINVAL;
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current->compat_robust_list = head;
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return 0;
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}
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COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
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compat_uptr_t __user *, head_ptr,
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compat_size_t __user *, len_ptr)
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{
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struct compat_robust_list_head __user *head;
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unsigned long ret;
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struct task_struct *p;
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rcu_read_lock();
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ret = -ESRCH;
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if (!pid)
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p = current;
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else {
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p = find_task_by_vpid(pid);
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if (!p)
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goto err_unlock;
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}
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ret = -EPERM;
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if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
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goto err_unlock;
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head = p->compat_robust_list;
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rcu_read_unlock();
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if (put_user(sizeof(*head), len_ptr))
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return -EFAULT;
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return put_user(ptr_to_compat(head), head_ptr);
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err_unlock:
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rcu_read_unlock();
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return ret;
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}
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#endif /* CONFIG_COMPAT */
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#ifdef CONFIG_COMPAT_32BIT_TIME
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SYSCALL_DEFINE6(futex_time32, u32 __user *, uaddr, int, op, u32, val,
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const struct old_timespec32 __user *, utime, u32 __user *, uaddr2,
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u32, val3)
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{
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int ret, cmd = op & FUTEX_CMD_MASK;
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ktime_t t, *tp = NULL;
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|
|
struct timespec64 ts;
|
||
|
|
|
||
|
|
if (utime && futex_cmd_has_timeout(cmd)) {
|
||
|
|
if (get_old_timespec32(&ts, utime))
|
||
|
|
return -EFAULT;
|
||
|
|
ret = futex_init_timeout(cmd, op, &ts, &t);
|
||
|
|
if (ret)
|
||
|
|
return ret;
|
||
|
|
tp = &t;
|
||
|
|
}
|
||
|
|
|
||
|
|
return do_futex(uaddr, op, val, tp, uaddr2, (unsigned long)utime, val3);
|
||
|
|
}
|
||
|
|
#endif /* CONFIG_COMPAT_32BIT_TIME */
|
||
|
|
|