proc: pagemap: Hold mmap_sem during page walk
In initial design, walk_page_range() was designed just for walking page table and it didn't require mmap_sem. Now, find_vma() etc.. are used in walk_page_range() and we need mmap_sem around it. This patch adds mmap_sem around walk_page_range(). Because /proc/<pid>/pagemap's callback routine use put_user(), we have to get rid of it to do sane fix. Changelog: 2010/Apr/2 - fixed start_vaddr and end overflow Changelog: 2010/Apr/1 - fixed start_vaddr calculation - removed unnecessary cast. - removed unnecessary change in smaps. - use GFP_TEMPORARY instead of GFP_KERNEL Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Matt Mackall <mpm@selenic.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: San Mehat <san@google.com> Cc: Brian Swetland <swetland@google.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> [ Fixed kmalloc failure return code as per Matt ] Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -406,6 +406,7 @@ static int show_smap(struct seq_file *m, void *v)
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memset(&mss, 0, sizeof mss);
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mss.vma = vma;
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/* mmap_sem is held in m_start */
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if (vma->vm_mm && !is_vm_hugetlb_page(vma))
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walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);
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@ -552,7 +553,8 @@ const struct file_operations proc_clear_refs_operations = {
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};
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struct pagemapread {
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u64 __user *out, *end;
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int pos, len;
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u64 *buffer;
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};
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#define PM_ENTRY_BYTES sizeof(u64)
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@ -575,10 +577,8 @@ struct pagemapread {
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static int add_to_pagemap(unsigned long addr, u64 pfn,
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struct pagemapread *pm)
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{
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if (put_user(pfn, pm->out))
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return -EFAULT;
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pm->out++;
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if (pm->out >= pm->end)
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pm->buffer[pm->pos++] = pfn;
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if (pm->pos >= pm->len)
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return PM_END_OF_BUFFER;
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return 0;
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}
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@ -720,21 +720,20 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long addr,
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* determine which areas of memory are actually mapped and llseek to
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* skip over unmapped regions.
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*/
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#define PAGEMAP_WALK_SIZE (PMD_SIZE)
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static ssize_t pagemap_read(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
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struct page **pages, *page;
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unsigned long uaddr, uend;
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struct mm_struct *mm;
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struct pagemapread pm;
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int pagecount;
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int ret = -ESRCH;
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struct mm_walk pagemap_walk = {};
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unsigned long src;
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unsigned long svpfn;
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unsigned long start_vaddr;
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unsigned long end_vaddr;
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int copied = 0;
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if (!task)
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goto out;
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@ -757,35 +756,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
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if (!mm)
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goto out_task;
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uaddr = (unsigned long)buf & PAGE_MASK;
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uend = (unsigned long)(buf + count);
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pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
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ret = 0;
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if (pagecount == 0)
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goto out_mm;
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pages = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
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pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
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pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
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ret = -ENOMEM;
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if (!pages)
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if (!pm.buffer)
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goto out_mm;
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down_read(¤t->mm->mmap_sem);
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ret = get_user_pages(current, current->mm, uaddr, pagecount,
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1, 0, pages, NULL);
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up_read(¤t->mm->mmap_sem);
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if (ret < 0)
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goto out_free;
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if (ret != pagecount) {
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pagecount = ret;
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ret = -EFAULT;
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goto out_pages;
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}
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pm.out = (u64 __user *)buf;
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pm.end = (u64 __user *)(buf + count);
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pagemap_walk.pmd_entry = pagemap_pte_range;
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pagemap_walk.pte_hole = pagemap_pte_hole;
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pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
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@ -807,23 +783,36 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
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* user buffer is tracked in "pm", and the walk
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* will stop when we hit the end of the buffer.
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*/
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ret = walk_page_range(start_vaddr, end_vaddr, &pagemap_walk);
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if (ret == PM_END_OF_BUFFER)
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ret = 0;
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/* don't need mmap_sem for these, but this looks cleaner */
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*ppos += (char __user *)pm.out - buf;
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if (!ret)
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ret = (char __user *)pm.out - buf;
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ret = 0;
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while (count && (start_vaddr < end_vaddr)) {
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int len;
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unsigned long end;
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out_pages:
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for (; pagecount; pagecount--) {
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page = pages[pagecount-1];
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if (!PageReserved(page))
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SetPageDirty(page);
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page_cache_release(page);
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pm.pos = 0;
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end = start_vaddr + PAGEMAP_WALK_SIZE;
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/* overflow ? */
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if (end < start_vaddr || end > end_vaddr)
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end = end_vaddr;
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down_read(&mm->mmap_sem);
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ret = walk_page_range(start_vaddr, end, &pagemap_walk);
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up_read(&mm->mmap_sem);
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start_vaddr = end;
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len = min(count, PM_ENTRY_BYTES * pm.pos);
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if (copy_to_user(buf, pm.buffer, len) < 0) {
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ret = -EFAULT;
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goto out_free;
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}
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copied += len;
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buf += len;
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count -= len;
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}
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*ppos += copied;
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if (!ret || ret == PM_END_OF_BUFFER)
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ret = copied;
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out_free:
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kfree(pages);
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kfree(pm.buffer);
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out_mm:
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mmput(mm);
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out_task:
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