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proc: pagemap: Hold mmap_sem during page walk

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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>
This commit is contained in:
KAMEZAWA Hiroyuki 2010-04-02 09:11:29 +09:00 committed by Linus Torvalds
parent 5e11611a5d
commit d82ef020cf
1 changed files with 37 additions and 48 deletions
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85
fs/proc/task_mmu.c
View File

@ -406,6 +406,7 @@ static int show_smap(struct seq_file *m, void *v)
memset(&mss, 0, sizeof mss);
mss.vma = vma;
/* mmap_sem is held in m_start */
if (vma->vm_mm && !is_vm_hugetlb_page(vma))
walk_page_range(vma->vm_start, vma->vm_end, &smaps_walk);
@ -552,7 +553,8 @@ const struct file_operations proc_clear_refs_operations = {
};
struct pagemapread {
u64 __user *out, *end;
int pos, len;
u64 *buffer;
};
#define PM_ENTRY_BYTES sizeof(u64)
@ -575,10 +577,8 @@ struct pagemapread {
static int add_to_pagemap(unsigned long addr, u64 pfn,
struct pagemapread *pm)
{
if (put_user(pfn, pm->out))
return -EFAULT;
pm->out++;
if (pm->out >= pm->end)
pm->buffer[pm->pos++] = pfn;
if (pm->pos >= pm->len)
return PM_END_OF_BUFFER;
return 0;
}
@ -720,21 +720,20 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long addr,
* determine which areas of memory are actually mapped and llseek to
* skip over unmapped regions.
*/
#define PAGEMAP_WALK_SIZE (PMD_SIZE)
static ssize_t pagemap_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
struct page **pages, *page;
unsigned long uaddr, uend;
struct mm_struct *mm;
struct pagemapread pm;
int pagecount;
int ret = -ESRCH;
struct mm_walk pagemap_walk = {};
unsigned long src;
unsigned long svpfn;
unsigned long start_vaddr;
unsigned long end_vaddr;
int copied = 0;
if (!task)
goto out;
@ -757,35 +756,12 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
if (!mm)
goto out_task;
uaddr = (unsigned long)buf & PAGE_MASK;
uend = (unsigned long)(buf + count);
pagecount = (PAGE_ALIGN(uend) - uaddr) / PAGE_SIZE;
ret = 0;
if (pagecount == 0)
goto out_mm;
pages = kcalloc(pagecount, sizeof(struct page *), GFP_KERNEL);
pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT);
pm.buffer = kmalloc(pm.len, GFP_TEMPORARY);
ret = -ENOMEM;
if (!pages)
if (!pm.buffer)
goto out_mm;
down_read(&current->mm->mmap_sem);
ret = get_user_pages(current, current->mm, uaddr, pagecount,
1, 0, pages, NULL);
up_read(&current->mm->mmap_sem);
if (ret < 0)
goto out_free;
if (ret != pagecount) {
pagecount = ret;
ret = -EFAULT;
goto out_pages;
}
pm.out = (u64 __user *)buf;
pm.end = (u64 __user *)(buf + count);
pagemap_walk.pmd_entry = pagemap_pte_range;
pagemap_walk.pte_hole = pagemap_pte_hole;
pagemap_walk.hugetlb_entry = pagemap_hugetlb_range;
@ -807,23 +783,36 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
* user buffer is tracked in "pm", and the walk
* will stop when we hit the end of the buffer.
*/
ret = walk_page_range(start_vaddr, end_vaddr, &pagemap_walk);
if (ret == PM_END_OF_BUFFER)
ret = 0;
/* don't need mmap_sem for these, but this looks cleaner */
*ppos += (char __user *)pm.out - buf;
if (!ret)
ret = (char __user *)pm.out - buf;
ret = 0;
while (count && (start_vaddr < end_vaddr)) {
int len;
unsigned long end;
out_pages:
for (; pagecount; pagecount--) {
page = pages[pagecount-1];
if (!PageReserved(page))
SetPageDirty(page);
page_cache_release(page);
pm.pos = 0;
end = start_vaddr + PAGEMAP_WALK_SIZE;
/* overflow ? */
if (end < start_vaddr || end > end_vaddr)
end = end_vaddr;
down_read(&mm->mmap_sem);
ret = walk_page_range(start_vaddr, end, &pagemap_walk);
up_read(&mm->mmap_sem);
start_vaddr = end;
len = min(count, PM_ENTRY_BYTES * pm.pos);
if (copy_to_user(buf, pm.buffer, len) < 0) {
ret = -EFAULT;
goto out_free;
}
copied += len;
buf += len;
count -= len;
}
*ppos += copied;
if (!ret || ret == PM_END_OF_BUFFER)
ret = copied;
out_free:
kfree(pages);
kfree(pm.buffer);
out_mm:
mmput(mm);
out_task: