Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [ 042/123] nfs: dont zero out the rest of the page if we hit the EOF on a DIO READ | Date | Wed, 9 Jan 2013 12:34:41 -0800 |
| |
3.7-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jeff Layton <jlayton@redhat.com>
commit 67fad106a219e083c91c79695bd1807dde1bf7b9 upstream.
Eryu provided a test program that would segfault when attempting to read past the EOF on file that was opened O_DIRECT. The buffer given to the read() call was on the stack, and when he attempted to read past it it would scribble over the rest of the stack page.
If we hit the end of the file on a DIO READ request, then we don't want to zero out the rest of the buffer. These aren't pagecache pages after all, and there's no guarantee that the buffers that were passed in represent entire pages.
Reported-by: Eryu Guan <eguan@redhat.com> Cc: Fred Isaman <iisaman@netapp.com> Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- fs/nfs/direct.c | 8 -------- 1 file changed, 8 deletions(-)
--- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -266,14 +266,6 @@ static void nfs_direct_read_completion(s struct nfs_page *req = nfs_list_entry(hdr->pages.next); struct page *page = req->wb_page; - if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) { - if (bytes > hdr->good_bytes) - zero_user(page, 0, PAGE_SIZE); - else if (hdr->good_bytes - bytes < PAGE_SIZE) - zero_user_segment(page, - hdr->good_bytes & ~PAGE_MASK, - PAGE_SIZE); - } if (!PageCompound(page)) { if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) { if (bytes < hdr->good_bytes)
| |