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nfs: disallow duplicate pages in pgio page vectors

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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>
This commit is contained in:
Weston Andros Adamson 2014-08-14 17:39:32 -04:00 committed by Trond Myklebust
parent 7c3af97525
commit bba5c1887a
1 changed files with 15 additions and 3 deletions
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18
fs/nfs/pagelist.c
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@ -724,10 +724,11 @@ 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))
@ -735,12 +736,23 @@ 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)))