From: Brice Goglin Date: Tue, 9 Dec 2008 21:14:23 +0000 (-0800) Subject: mm: no get_user/put_user while holding mmap_sem in do_pages_stat? X-Git-Tag: v2.6.28-rc8~20 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=80bba1290ab5122c60cdb73332b26d288dc8aedd;p=linux-2.6-omap-h63xx.git mm: no get_user/put_user while holding mmap_sem in do_pages_stat? Since commit 2f007e74bb85b9fc4eab28524052161703300f1a, 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: Brice Goglin Cc: Christoph Lameter Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/migrate.c b/mm/migrate.c index 1e0d6b237f4..d8f07667fc8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -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; }