From 49a068f82a1d30eb585d7804b05948376be6cf9a Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Mon, 22 Dec 2014 16:14:51 -0500 Subject: [PATCH] rpc: fix xdr_truncate_encode to handle buffer ending on page boundary MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit A struct xdr_stream at a page boundary might point to the end of one page or the beginning of the next, but xdr_truncate_encode isn't prepared to handle the former. This can cause corruption of NFSv4 READDIR replies in the case that a readdir entry that would have exceeded the client's dircount/maxcount limit would have ended exactly on a 4k page boundary. You're more likely to hit this case on large directories. Other xdr_truncate_encode callers are probably also affected. Reported-by: Holger Hoffstätte Tested-by: Holger Hoffstätte Fixes: 3e19ce762b53 "rpc: xdr_truncate_encode" Cc: stable@vger.kernel.org Signed-off-by: J. Bruce Fields --- net/sunrpc/xdr.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 1cb6124..4439ac4 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -606,7 +606,7 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len) struct kvec *head = buf->head; struct kvec *tail = buf->tail; int fraglen; - int new, old; + int new; if (len > buf->len) { WARN_ON_ONCE(1); @@ -629,8 +629,8 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len) buf->len -= fraglen; new = buf->page_base + buf->page_len; - old = new + fraglen; - xdr->page_ptr -= (old >> PAGE_SHIFT) - (new >> PAGE_SHIFT); + + xdr->page_ptr = buf->pages + (new >> PAGE_SHIFT); if (buf->page_len) { xdr->p = page_address(*xdr->page_ptr); -- 2.7.4