Commit 49a068f8 authored Dec 22, 2014 by J. Bruce Fields

rpc: fix xdr_truncate_encode to handle buffer ending on page boundary



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 <holger.hoffstaette@googlemail.com>
Tested-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Fixes: 3e19ce76 "rpc: xdr_truncate_encode"
Cc: stable@vger.kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent 94ae1db2

net/sunrpc/xdr.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -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);