From: Hugh Dickins <hugh@veritas.com>
Date: Tue, 11 Oct 2005 18:16:26 +0000 (+0100)
Subject: [PATCH] Don't map the same page too much
X-Git-Tag: v2.6.14-rc5~76
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f5154a98a1931641f0448f6512294a15279110d7;p=linux-2.6

[PATCH] Don't map the same page too much

Refuse to install a page into a mapping if the mapping count is already
ridiculously large.

You probably cannot trigger this on 32-bit architectures, but on a
64-bit setup we should protect against it.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/mm/fremap.c b/mm/fremap.c
index 3235fb77c1..ab23a0673c 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -89,6 +89,9 @@ int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 	if (!page->mapping || page->index >= size)
 		goto err_unlock;
+	err = -ENOMEM;
+	if (page_mapcount(page) > INT_MAX/2)
+		goto err_unlock;
 
 	zap_pte(mm, vma, addr, pte);