nfs: disallow duplicate pages in pgio page vectors

commit bba5c1887a925a9945d22217d38d58d8b3ba1043 upstream.

Adjacent requests that share the same page are allowed, but should only
use one entry in the page vector. This avoids overruning the page
vector - it is sized based on how many bytes there are, not by
request count.

This fixes issues that manifest as "Redzone overwritten" bugs (the
vector overrun) and hangs waiting on page read / write, as it waits on
the same page more than once.

This also adds bounds checking to the page vector with a graceful failure
(WARN_ON_ONCE and pgio error returned to application).

Reported-by: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index f56b6351b660bdaca98810fe1a9af09c9d9a4ded..91e84b3ad63e43b09e950b3d0267b53ec80c2f35 100644 (file)
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -734,10 +734,11 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
                     struct nfs_pgio_header *hdr)
 {
        struct nfs_page         *req;
-       struct page             **pages;
+       struct page             **pages,
+                               *last_page;
        struct list_head *head = &desc->pg_list;
        struct nfs_commit_info cinfo;
-       unsigned int pagecount;
+       unsigned int pagecount, pageused;
 
        pagecount = nfs_page_array_len(desc->pg_base, desc->pg_count);
        if (!nfs_pgarray_set(&hdr->page_array, pagecount))
@@ -745,12 +746,23 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
 
        nfs_init_cinfo(&cinfo, desc->pg_inode, desc->pg_dreq);
        pages = hdr->page_array.pagevec;
+       last_page = NULL;
+       pageused = 0;
        while (!list_empty(head)) {
                req = nfs_list_entry(head->next);
                nfs_list_remove_request(req);
                nfs_list_add_request(req, &hdr->pages);
-               *pages++ = req->wb_page;
+
+               if (WARN_ON_ONCE(pageused >= pagecount))
+                       return nfs_pgio_error(desc, hdr);
+
+               if (!last_page || last_page != req->wb_page) {
+                       *pages++ = last_page = req->wb_page;
+                       pageused++;
+               }
        }
+       if (WARN_ON_ONCE(pageused != pagecount))
+               return nfs_pgio_error(desc, hdr);
 
        if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
            (desc->pg_moreio || nfs_reqs_to_commit(&cinfo)))