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@xxxxxx>
Signed-off-by: Weston Andros Adamson <dros@xxxxxxxxxxxxxxx>
---
fs/nfs/pagelist.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index e0c2e72..73476df 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -733,10 +733,11 @@ 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))
@@ -744,11 +745,26 @@ 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 (pageused >= pagecount) {
+ WARN_ON_ONCE(1);
+ return nfs_pgio_error(desc, hdr);
+ }
+
+ if (!last_page || last_page != req->wb_page) {
+ *pages++ = last_page = req->wb_page;
+ pageused++;
+ }
+ }
+ if (pageused != pagecount) {
+ WARN_ON_ONCE(1);
+ return nfs_pgio_error(desc, hdr);
}
if ((desc->pg_ioflags & FLUSH_COND_STABLE) &&
--
1.8.5.2 (Apple Git-48)
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
