Fix OOPS in mmap_region() when merging adjacent VM_LOCKED file segments
[linux-2.6.git] / mm / mremap.c
1 /*
2  *      mm/mremap.c
3  *
4  *      (C) Copyright 1996 Linus Torvalds
5  *
6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
8  */
9
10 #include <linux/mm.h>
11 #include <linux/hugetlb.h>
12 #include <linux/slab.h>
13 #include <linux/shm.h>
14 #include <linux/mman.h>
15 #include <linux/swap.h>
16 #include <linux/capability.h>
17 #include <linux/fs.h>
18 #include <linux/highmem.h>
19 #include <linux/security.h>
20 #include <linux/syscalls.h>
21 #include <linux/mmu_notifier.h>
22
23 #include <asm/uaccess.h>
24 #include <asm/cacheflush.h>
25 #include <asm/tlbflush.h>
26
27 #include "internal.h"
28
29 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
30 {
31         pgd_t *pgd;
32         pud_t *pud;
33         pmd_t *pmd;
34
35         pgd = pgd_offset(mm, addr);
36         if (pgd_none_or_clear_bad(pgd))
37                 return NULL;
38
39         pud = pud_offset(pgd, addr);
40         if (pud_none_or_clear_bad(pud))
41                 return NULL;
42
43         pmd = pmd_offset(pud, addr);
44         if (pmd_none_or_clear_bad(pmd))
45                 return NULL;
46
47         return pmd;
48 }
49
50 static pmd_t *alloc_new_pmd(struct mm_struct *mm, unsigned long addr)
51 {
52         pgd_t *pgd;
53         pud_t *pud;
54         pmd_t *pmd;
55
56         pgd = pgd_offset(mm, addr);
57         pud = pud_alloc(mm, pgd, addr);
58         if (!pud)
59                 return NULL;
60
61         pmd = pmd_alloc(mm, pud, addr);
62         if (!pmd)
63                 return NULL;
64
65         if (!pmd_present(*pmd) && __pte_alloc(mm, pmd, addr))
66                 return NULL;
67
68         return pmd;
69 }
70
71 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
72                 unsigned long old_addr, unsigned long old_end,
73                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
74                 unsigned long new_addr)
75 {
76         struct address_space *mapping = NULL;
77         struct mm_struct *mm = vma->vm_mm;
78         pte_t *old_pte, *new_pte, pte;
79         spinlock_t *old_ptl, *new_ptl;
80         unsigned long old_start;
81
82         old_start = old_addr;
83         mmu_notifier_invalidate_range_start(vma->vm_mm,
84                                             old_start, old_end);
85         if (vma->vm_file) {
86                 /*
87                  * Subtle point from Rajesh Venkatasubramanian: before
88                  * moving file-based ptes, we must lock vmtruncate out,
89                  * since it might clean the dst vma before the src vma,
90                  * and we propagate stale pages into the dst afterward.
91                  */
92                 mapping = vma->vm_file->f_mapping;
93                 spin_lock(&mapping->i_mmap_lock);
94                 if (new_vma->vm_truncate_count &&
95                     new_vma->vm_truncate_count != vma->vm_truncate_count)
96                         new_vma->vm_truncate_count = 0;
97         }
98
99         /*
100          * We don't have to worry about the ordering of src and dst
101          * pte locks because exclusive mmap_sem prevents deadlock.
102          */
103         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
104         new_pte = pte_offset_map_nested(new_pmd, new_addr);
105         new_ptl = pte_lockptr(mm, new_pmd);
106         if (new_ptl != old_ptl)
107                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
108         arch_enter_lazy_mmu_mode();
109
110         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
111                                    new_pte++, new_addr += PAGE_SIZE) {
112                 if (pte_none(*old_pte))
113                         continue;
114                 pte = ptep_clear_flush(vma, old_addr, old_pte);
115                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
116                 set_pte_at(mm, new_addr, new_pte, pte);
117         }
118
119         arch_leave_lazy_mmu_mode();
120         if (new_ptl != old_ptl)
121                 spin_unlock(new_ptl);
122         pte_unmap_nested(new_pte - 1);
123         pte_unmap_unlock(old_pte - 1, old_ptl);
124         if (mapping)
125                 spin_unlock(&mapping->i_mmap_lock);
126         mmu_notifier_invalidate_range_end(vma->vm_mm, old_start, old_end);
127 }
128
129 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
130
131 unsigned long move_page_tables(struct vm_area_struct *vma,
132                 unsigned long old_addr, struct vm_area_struct *new_vma,
133                 unsigned long new_addr, unsigned long len)
134 {
135         unsigned long extent, next, old_end;
136         pmd_t *old_pmd, *new_pmd;
137
138         old_end = old_addr + len;
139         flush_cache_range(vma, old_addr, old_end);
140
141         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
142                 cond_resched();
143                 next = (old_addr + PMD_SIZE) & PMD_MASK;
144                 if (next - 1 > old_end)
145                         next = old_end;
146                 extent = next - old_addr;
147                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
148                 if (!old_pmd)
149                         continue;
150                 new_pmd = alloc_new_pmd(vma->vm_mm, new_addr);
151                 if (!new_pmd)
152                         break;
153                 next = (new_addr + PMD_SIZE) & PMD_MASK;
154                 if (extent > next - new_addr)
155                         extent = next - new_addr;
156                 if (extent > LATENCY_LIMIT)
157                         extent = LATENCY_LIMIT;
158                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
159                                 new_vma, new_pmd, new_addr);
160         }
161
162         return len + old_addr - old_end;        /* how much done */
163 }
164
165 static unsigned long move_vma(struct vm_area_struct *vma,
166                 unsigned long old_addr, unsigned long old_len,
167                 unsigned long new_len, unsigned long new_addr)
168 {
169         struct mm_struct *mm = vma->vm_mm;
170         struct vm_area_struct *new_vma;
171         unsigned long vm_flags = vma->vm_flags;
172         unsigned long new_pgoff;
173         unsigned long moved_len;
174         unsigned long excess = 0;
175         unsigned long hiwater_vm;
176         int split = 0;
177
178         /*
179          * We'd prefer to avoid failure later on in do_munmap:
180          * which may split one vma into three before unmapping.
181          */
182         if (mm->map_count >= sysctl_max_map_count - 3)
183                 return -ENOMEM;
184
185         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
186         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
187         if (!new_vma)
188                 return -ENOMEM;
189
190         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
191         if (moved_len < old_len) {
192                 /*
193                  * On error, move entries back from new area to old,
194                  * which will succeed since page tables still there,
195                  * and then proceed to unmap new area instead of old.
196                  */
197                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
198                 vma = new_vma;
199                 old_len = new_len;
200                 old_addr = new_addr;
201                 new_addr = -ENOMEM;
202         }
203
204         /* Conceal VM_ACCOUNT so old reservation is not undone */
205         if (vm_flags & VM_ACCOUNT) {
206                 vma->vm_flags &= ~VM_ACCOUNT;
207                 excess = vma->vm_end - vma->vm_start - old_len;
208                 if (old_addr > vma->vm_start &&
209                     old_addr + old_len < vma->vm_end)
210                         split = 1;
211         }
212
213         /*
214          * If we failed to move page tables we still do total_vm increment
215          * since do_munmap() will decrement it by old_len == new_len.
216          *
217          * Since total_vm is about to be raised artificially high for a
218          * moment, we need to restore high watermark afterwards: if stats
219          * are taken meanwhile, total_vm and hiwater_vm appear too high.
220          * If this were a serious issue, we'd add a flag to do_munmap().
221          */
222         hiwater_vm = mm->hiwater_vm;
223         mm->total_vm += new_len >> PAGE_SHIFT;
224         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
225
226         if (do_munmap(mm, old_addr, old_len) < 0) {
227                 /* OOM: unable to split vma, just get accounts right */
228                 vm_unacct_memory(excess >> PAGE_SHIFT);
229                 excess = 0;
230         }
231         mm->hiwater_vm = hiwater_vm;
232
233         /* Restore VM_ACCOUNT if one or two pieces of vma left */
234         if (excess) {
235                 vma->vm_flags |= VM_ACCOUNT;
236                 if (split)
237                         vma->vm_next->vm_flags |= VM_ACCOUNT;
238         }
239
240         if (vm_flags & VM_LOCKED) {
241                 mm->locked_vm += new_len >> PAGE_SHIFT;
242                 if (new_len > old_len)
243                         mlock_vma_pages_range(new_vma, new_addr + old_len,
244                                                        new_addr + new_len);
245         }
246
247         return new_addr;
248 }
249
250 /*
251  * Expand (or shrink) an existing mapping, potentially moving it at the
252  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
253  *
254  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
255  * This option implies MREMAP_MAYMOVE.
256  */
257 unsigned long do_mremap(unsigned long addr,
258         unsigned long old_len, unsigned long new_len,
259         unsigned long flags, unsigned long new_addr)
260 {
261         struct mm_struct *mm = current->mm;
262         struct vm_area_struct *vma;
263         unsigned long ret = -EINVAL;
264         unsigned long charged = 0;
265
266         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
267                 goto out;
268
269         if (addr & ~PAGE_MASK)
270                 goto out;
271
272         old_len = PAGE_ALIGN(old_len);
273         new_len = PAGE_ALIGN(new_len);
274
275         /*
276          * We allow a zero old-len as a special case
277          * for DOS-emu "duplicate shm area" thing. But
278          * a zero new-len is nonsensical.
279          */
280         if (!new_len)
281                 goto out;
282
283         /* new_addr is only valid if MREMAP_FIXED is specified */
284         if (flags & MREMAP_FIXED) {
285                 if (new_addr & ~PAGE_MASK)
286                         goto out;
287                 if (!(flags & MREMAP_MAYMOVE))
288                         goto out;
289
290                 if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
291                         goto out;
292
293                 /* Check if the location we're moving into overlaps the
294                  * old location at all, and fail if it does.
295                  */
296                 if ((new_addr <= addr) && (new_addr+new_len) > addr)
297                         goto out;
298
299                 if ((addr <= new_addr) && (addr+old_len) > new_addr)
300                         goto out;
301
302                 ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
303                 if (ret)
304                         goto out;
305
306                 ret = do_munmap(mm, new_addr, new_len);
307                 if (ret)
308                         goto out;
309         }
310
311         /*
312          * Always allow a shrinking remap: that just unmaps
313          * the unnecessary pages..
314          * do_munmap does all the needed commit accounting
315          */
316         if (old_len >= new_len) {
317                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
318                 if (ret && old_len != new_len)
319                         goto out;
320                 ret = addr;
321                 if (!(flags & MREMAP_FIXED) || (new_addr == addr))
322                         goto out;
323                 old_len = new_len;
324         }
325
326         /*
327          * Ok, we need to grow..  or relocate.
328          */
329         ret = -EFAULT;
330         vma = find_vma(mm, addr);
331         if (!vma || vma->vm_start > addr)
332                 goto out;
333         if (is_vm_hugetlb_page(vma)) {
334                 ret = -EINVAL;
335                 goto out;
336         }
337         /* We can't remap across vm area boundaries */
338         if (old_len > vma->vm_end - addr)
339                 goto out;
340         if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) {
341                 if (new_len > old_len)
342                         goto out;
343         }
344         if (vma->vm_flags & VM_LOCKED) {
345                 unsigned long locked, lock_limit;
346                 locked = mm->locked_vm << PAGE_SHIFT;
347                 lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
348                 locked += new_len - old_len;
349                 ret = -EAGAIN;
350                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
351                         goto out;
352         }
353         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT)) {
354                 ret = -ENOMEM;
355                 goto out;
356         }
357
358         if (vma->vm_flags & VM_ACCOUNT) {
359                 charged = (new_len - old_len) >> PAGE_SHIFT;
360                 if (security_vm_enough_memory(charged))
361                         goto out_nc;
362         }
363
364         /* old_len exactly to the end of the area..
365          * And we're not relocating the area.
366          */
367         if (old_len == vma->vm_end - addr &&
368             !((flags & MREMAP_FIXED) && (addr != new_addr)) &&
369             (old_len != new_len || !(flags & MREMAP_MAYMOVE))) {
370                 unsigned long max_addr = TASK_SIZE;
371                 if (vma->vm_next)
372                         max_addr = vma->vm_next->vm_start;
373                 /* can we just expand the current mapping? */
374                 if (max_addr - addr >= new_len) {
375                         int pages = (new_len - old_len) >> PAGE_SHIFT;
376
377                         vma_adjust(vma, vma->vm_start,
378                                 addr + new_len, vma->vm_pgoff, NULL);
379
380                         mm->total_vm += pages;
381                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
382                         if (vma->vm_flags & VM_LOCKED) {
383                                 mm->locked_vm += pages;
384                                 mlock_vma_pages_range(vma, addr + old_len,
385                                                    addr + new_len);
386                         }
387                         ret = addr;
388                         goto out;
389                 }
390         }
391
392         /*
393          * We weren't able to just expand or shrink the area,
394          * we need to create a new one and move it..
395          */
396         ret = -ENOMEM;
397         if (flags & MREMAP_MAYMOVE) {
398                 if (!(flags & MREMAP_FIXED)) {
399                         unsigned long map_flags = 0;
400                         if (vma->vm_flags & VM_MAYSHARE)
401                                 map_flags |= MAP_SHARED;
402
403                         new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
404                                                 vma->vm_pgoff, map_flags);
405                         if (new_addr & ~PAGE_MASK) {
406                                 ret = new_addr;
407                                 goto out;
408                         }
409
410                         ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
411                         if (ret)
412                                 goto out;
413                 }
414                 ret = move_vma(vma, addr, old_len, new_len, new_addr);
415         }
416 out:
417         if (ret & ~PAGE_MASK)
418                 vm_unacct_memory(charged);
419 out_nc:
420         return ret;
421 }
422
423 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
424                 unsigned long, new_len, unsigned long, flags,
425                 unsigned long, new_addr)
426 {
427         unsigned long ret;
428
429         down_write(&current->mm->mmap_sem);
430         ret = do_mremap(addr, old_len, new_len, flags, new_addr);
431         up_write(&current->mm->mmap_sem);
432         return ret;
433 }