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Commit 80bba129 authored by Brice Goglin's avatar Brice Goglin Committed by Linus Torvalds
Browse files

mm: no get_user/put_user while holding mmap_sem in do_pages_stat? 



Since commit 2f007e74, do_pages_stat()
gets the page address from user-space and puts the corresponding status
back while holding the mmap_sem for read.  There is no need to hold
mmap_sem there while some page-faults may occur.

This patch adds a temporary address and status buffer so as to only
hold mmap_sem while working on these kernel buffers.  This is
implemented by extracting do_pages_stat_array() out of do_pages_stat().

Signed-off-by: default avatarBrice Goglin <Brice.Goglin@inria.fr>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 52b9582d

mm/migrate.c

+46 −13
Original line number Diff line number Diff line
@@ -987,25 +987,18 @@ out: 
/*

 * Determine the nodes of an array of pages and store it in an array of status.

 */

static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,

			 const void __user * __user *pages,

			 int __user *status)

static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,

				const void __user **pages, int *status)

{

	unsigned long i;

	int err;



	down_read(&mm->mmap_sem);



	for (i = 0; i < nr_pages; i++) {

		const void __user *p;

		unsigned long addr;

		unsigned long addr = (unsigned long)(*pages);

		struct vm_area_struct *vma;

		struct page *page;



		err = -EFAULT;

		if (get_user(p, pages+i))

			goto out;

		addr = (unsigned long) p;

		int err;



		vma = find_vma(mm, addr);

		if (!vma)
@@ -1024,12 +1017,52 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, 


		err = page_to_nid(page);

set_status:

		put_user(err, status+i);

		*status = err;



		pages++;

		status++;

	}



	up_read(&mm->mmap_sem);

}



/*

 * Determine the nodes of a user array of pages and store it in

 * a user array of status.

 */

static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,

			 const void __user * __user *pages,

			 int __user *status)

{

#define DO_PAGES_STAT_CHUNK_NR 16

	const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR];

	int chunk_status[DO_PAGES_STAT_CHUNK_NR];

	unsigned long i, chunk_nr = DO_PAGES_STAT_CHUNK_NR;

	int err;



	for (i = 0; i < nr_pages; i += chunk_nr) {

		if (chunk_nr + i > nr_pages)

			chunk_nr = nr_pages - i;



		err = copy_from_user(chunk_pages, &pages[i],

				     chunk_nr * sizeof(*chunk_pages));

		if (err) {

			err = -EFAULT;

			goto out;

		}



		do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status);



		err = copy_to_user(&status[i], chunk_status,

				   chunk_nr * sizeof(*chunk_status));

		if (err) {

			err = -EFAULT;

			goto out;

		}

	}

	err = 0;



out:

	up_read(&mm->mmap_sem);

	return err;

}