Commit ac9645c8 authored Dec 05, 2020 by Dan Aloni Committed by Trond Myklebust Dec 14, 2020

sunrpc: fix xs_read_xdr_buf for partial pages receive



When receiving pages data, return value 'ret' when positive includes
`buf->page_base`, so we should subtract that before it is used for
changing `offset` and comparing against `want`.

This was discovered on the very rare cases where the server returned a
chunk of bytes that when added to the already received amount of bytes
for the pages happened to match the current `recv.len`, for example
on this case:

     buf->page_base : 258356
     actually received from socket: 1740
     ret : 260096
     want : 260096

In this case neither of the two 'if ... goto out' trigger, and we
continue to tail parsing.

Worth to mention that the ensuing EMSGSIZE from the continued execution of
`xs_read_xdr_buf` may be observed by an application due to 4 superfluous
bytes being added to the pages data.

Fixes: 277e4ab7 ("SUNRPC: Simplify TCP receive code by switching to using iterators")
Signed-off-by: Dan Aloni <dan@kernelim.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

parent fa94a951

net/sunrpc/xprtsock.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -433,7 +433,8 @@ xs_read_xdr_buf(struct socket sock, struct msghdr msg, int flags,
		if (ret <= 0)
		goto sock_err;
		xs_flush_bvec(buf->bvec, ret, seek + buf->page_base);
		offset += ret - buf->page_base;
		ret -= buf->page_base;
		offset += ret;
		if (offset == count \|\| msg->msg_flags & (MSG_EOR\|MSG_TRUNC))
		goto out;
		if (ret != want)

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