From: Weston Andros Adamson <[email protected]> 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 <[email protected]> Signed-off-by: Weston Andros Adamson <[email protected]> Signed-off-by: Trond Myklebust <[email protected]> --- fs/nfs/pagelist.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c index f56b6351b660..91e84b3ad63e 100644 --- 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))) -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
