From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joel Becker Date: Mon, 25 Jan 2010 19:19:56 -0800 Subject: [Ocfs2-devel] [PATCH] ocfs2: Fix memory overflow in cow_by_page. In-Reply-To: <1264057166-21316-1-git-send-email-tao.ma@oracle.com> References: <1264057166-21316-1-git-send-email-tao.ma@oracle.com> Message-ID: <20100126031956.GC15982@mail.oracle.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com On Thu, Jan 21, 2010 at 02:59:26PM +0800, Tao Ma wrote: > In ocfs2_duplicate_clusters_by_page, we calculate map_end > by shifting page_index. But actually in case we meet with > a large offset(say in a i686 box, poff_t is only 32 bits > and page_index=2056240), we will overflow. So change it > by adding PAGE_CACHE_SIZE to offset. > > Signed-off-by: Tao Ma > --- > fs/ocfs2/refcounttree.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c > index 74db2be..6db863d 100644 > --- a/fs/ocfs2/refcounttree.c > +++ b/fs/ocfs2/refcounttree.c > @@ -2945,7 +2945,7 @@ static int ocfs2_duplicate_clusters_by_page(handle_t *handle, > > while (offset < end) { > page_index = offset >> PAGE_CACHE_SHIFT; > - map_end = (page_index + 1) << PAGE_CACHE_SHIFT; > + map_end = offset + PAGE_CACHE_SIZE; First, we can't be computing by offset, because map_end is supposed to be page bounded, right? Also, what if we have an offset that is the last page possible? Won't that wrap as well, setting map_end to 0? Why aren't we computing map_end like we compute end, as a loff_t value? page_index = offset >> PAGE_CACHE_SHIFT; - map_end = (page_index + 1) << PAGE_CACHE_SHIFT; + map_end = ((loff_t)page_index + 1) << PAGE_CACHE_SHIFT; if (map_end > end) map_end = end; The map_end>end check will catch anything too big. Joel -- "You don't make the poor richer by making the rich poorer." - Sir Winston Churchill Joel Becker Principal Software Developer Oracle E-mail: joel.becker at oracle.com Phone: (650) 506-8127