From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx102.postini.com [74.125.245.102]) by kanga.kvack.org (Postfix) with SMTP id 3288E6B0031 for ; Fri, 9 Aug 2013 01:16:43 -0400 (EDT) Received: by mail-bk0-f65.google.com with SMTP id r7so424647bkg.4 for ; Thu, 08 Aug 2013 22:16:41 -0700 (PDT) MIME-Version: 1.0 Date: Fri, 9 Aug 2013 13:16:41 +0800 Message-ID: Subject: [PATCH 1/1] pagemap: fix buffer overflow in add_page_map() From: yonghua zheng Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Motohiro KOSAKI Hi, Recently we met quite a lot of random kernel panic issues after enable CONFIG_PROC_PAGE_MONITOR in kernel, after debuggint sometime we found this has something to do with following bug in pagemap: In struc pagemapread: struct pagemapread { int pos, len; pagemap_entry_t *buffer; bool v2; }; pos is number of PM_ENTRY_BYTES in buffer, but len is the size of buffer, it is a mistake to compare pos and len in add_page_map() for checking buffer is full or not, and this can lead to buffer overflow and random kernel panic issue. Correct len to be total number of PM_ENTRY_BYTES in buffer. Signed-off-by: Yonghua Zheng --- fs/proc/task_mmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index dbf61f6..cb98853 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1116,8 +1116,8 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, goto out_task; pm.v2 = soft_dirty_cleared; - pm.len = PM_ENTRY_BYTES * (PAGEMAP_WALK_SIZE >> PAGE_SHIFT); - pm.buffer = kmalloc(pm.len, GFP_TEMPORARY); + pm.len = (PAGEMAP_WALK_SIZE >> PAGE_SHIFT); + pm.buffer = kmalloc(pm.len * PM_ENTRY_BYTES, GFP_TEMPORARY); ret = -ENOMEM; if (!pm.buffer) goto out_task; -- 1.7.9.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org