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Linux/kernel/futex_compat.c

  1 /*
  2  * linux/kernel/futex_compat.c
  3  *
  4  * Futex compatibililty routines.
  5  *
  6  * Copyright 2006, Red Hat, Inc., Ingo Molnar
  7  */
  8 
  9 #include <linux/linkage.h>
 10 #include <linux/compat.h>
 11 #include <linux/nsproxy.h>
 12 #include <linux/futex.h>
 13 #include <linux/ptrace.h>
 14 #include <linux/syscalls.h>
 15 
 16 #include <linux/uaccess.h>
 17 
 18 
 19 /*
 20  * Fetch a robust-list pointer. Bit 0 signals PI futexes:
 21  */
 22 static inline int
 23 fetch_robust_entry(compat_uptr_t *uentry, struct robust_list __user **entry,
 24                    compat_uptr_t __user *head, unsigned int *pi)
 25 {
 26         if (get_user(*uentry, head))
 27                 return -EFAULT;
 28 
 29         *entry = compat_ptr((*uentry) & ~1);
 30         *pi = (unsigned int)(*uentry) & 1;
 31 
 32         return 0;
 33 }
 34 
 35 static void __user *futex_uaddr(struct robust_list __user *entry,
 36                                 compat_long_t futex_offset)
 37 {
 38         compat_uptr_t base = ptr_to_compat(entry);
 39         void __user *uaddr = compat_ptr(base + futex_offset);
 40 
 41         return uaddr;
 42 }
 43 
 44 /*
 45  * Walk curr->robust_list (very carefully, it's a userspace list!)
 46  * and mark any locks found there dead, and notify any waiters.
 47  *
 48  * We silently return on any sign of list-walking problem.
 49  */
 50 void compat_exit_robust_list(struct task_struct *curr)
 51 {
 52         struct compat_robust_list_head __user *head = curr->compat_robust_list;
 53         struct robust_list __user *entry, *next_entry, *pending;
 54         unsigned int limit = ROBUST_LIST_LIMIT, pi, pip;
 55         unsigned int uninitialized_var(next_pi);
 56         compat_uptr_t uentry, next_uentry, upending;
 57         compat_long_t futex_offset;
 58         int rc;
 59 
 60         if (!futex_cmpxchg_enabled)
 61                 return;
 62 
 63         /*
 64          * Fetch the list head (which was registered earlier, via
 65          * sys_set_robust_list()):
 66          */
 67         if (fetch_robust_entry(&uentry, &entry, &head->list.next, &pi))
 68                 return;
 69         /*
 70          * Fetch the relative futex offset:
 71          */
 72         if (get_user(futex_offset, &head->futex_offset))
 73                 return;
 74         /*
 75          * Fetch any possibly pending lock-add first, and handle it
 76          * if it exists:
 77          */
 78         if (fetch_robust_entry(&upending, &pending,
 79                                &head->list_op_pending, &pip))
 80                 return;
 81 
 82         next_entry = NULL;      /* avoid warning with gcc */
 83         while (entry != (struct robust_list __user *) &head->list) {
 84                 /*
 85                  * Fetch the next entry in the list before calling
 86                  * handle_futex_death:
 87                  */
 88                 rc = fetch_robust_entry(&next_uentry, &next_entry,
 89                         (compat_uptr_t __user *)&entry->next, &next_pi);
 90                 /*
 91                  * A pending lock might already be on the list, so
 92                  * dont process it twice:
 93                  */
 94                 if (entry != pending) {
 95                         void __user *uaddr = futex_uaddr(entry, futex_offset);
 96 
 97                         if (handle_futex_death(uaddr, curr, pi))
 98                                 return;
 99                 }
100                 if (rc)
101                         return;
102                 uentry = next_uentry;
103                 entry = next_entry;
104                 pi = next_pi;
105                 /*
106                  * Avoid excessively long or circular lists:
107                  */
108                 if (!--limit)
109                         break;
110 
111                 cond_resched();
112         }
113         if (pending) {
114                 void __user *uaddr = futex_uaddr(pending, futex_offset);
115 
116                 handle_futex_death(uaddr, curr, pip);
117         }
118 }
119 
120 COMPAT_SYSCALL_DEFINE2(set_robust_list,
121                 struct compat_robust_list_head __user *, head,
122                 compat_size_t, len)
123 {
124         if (!futex_cmpxchg_enabled)
125                 return -ENOSYS;
126 
127         if (unlikely(len != sizeof(*head)))
128                 return -EINVAL;
129 
130         current->compat_robust_list = head;
131 
132         return 0;
133 }
134 
135 COMPAT_SYSCALL_DEFINE3(get_robust_list, int, pid,
136                         compat_uptr_t __user *, head_ptr,
137                         compat_size_t __user *, len_ptr)
138 {
139         struct compat_robust_list_head __user *head;
140         unsigned long ret;
141         struct task_struct *p;
142 
143         if (!futex_cmpxchg_enabled)
144                 return -ENOSYS;
145 
146         rcu_read_lock();
147 
148         ret = -ESRCH;
149         if (!pid)
150                 p = current;
151         else {
152                 p = find_task_by_vpid(pid);
153                 if (!p)
154                         goto err_unlock;
155         }
156 
157         ret = -EPERM;
158         if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS))
159                 goto err_unlock;
160 
161         head = p->compat_robust_list;
162         rcu_read_unlock();
163 
164         if (put_user(sizeof(*head), len_ptr))
165                 return -EFAULT;
166         return put_user(ptr_to_compat(head), head_ptr);
167 
168 err_unlock:
169         rcu_read_unlock();
170 
171         return ret;
172 }
173 
174 COMPAT_SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
175                 struct compat_timespec __user *, utime, u32 __user *, uaddr2,
176                 u32, val3)
177 {
178         struct timespec ts;
179         ktime_t t, *tp = NULL;
180         int val2 = 0;
181         int cmd = op & FUTEX_CMD_MASK;
182 
183         if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
184                       cmd == FUTEX_WAIT_BITSET ||
185                       cmd == FUTEX_WAIT_REQUEUE_PI)) {
186                 if (compat_get_timespec(&ts, utime))
187                         return -EFAULT;
188                 if (!timespec_valid(&ts))
189                         return -EINVAL;
190 
191                 t = timespec_to_ktime(ts);
192                 if (cmd == FUTEX_WAIT)
193                         t = ktime_add_safe(ktime_get(), t);
194                 tp = &t;
195         }
196         if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
197             cmd == FUTEX_CMP_REQUEUE_PI || cmd == FUTEX_WAKE_OP)
198                 val2 = (int) (unsigned long) utime;
199 
200         return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
201 }
202 

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