From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 90bfc37b5ab91c1a6165e3e5cfc49bf04571b762 ]
Ensure that stream-based argument decoding can't go past the actual end of the receive buffer. xdr_init_decode's calculation of the value of xdr->end over-estimates the end of the buffer because the Linux kernel RPC server code does not remove the size of the RPC header from rqstp->rq_arg before calling the upper layer's dispatcher.
The server-side still uses the svc_getnl() macros to decode the RPC call header. These macros reduce the length of the head iov but do not update the total length of the message in the buffer (buf->len).
A proper fix for this would be to replace the use of svc_getnl() and friends in the RPC header decoder, but that would be a large and invasive change that would be difficult to backport.
Fixes: 5191955d6fc6 ("SUNRPC: Prepare for xdr_stream-style decoding on the server-side") Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/sunrpc/svc.h | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 01f09adccc63..6be55d0e73fd 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -566,16 +566,27 @@ static inline void svc_reserve_auth(struct svc_rqst *rqstp, int space) }
/** - * svcxdr_init_decode - Prepare an xdr_stream for svc Call decoding + * svcxdr_init_decode - Prepare an xdr_stream for Call decoding * @rqstp: controlling server RPC transaction context * + * This function currently assumes the RPC header in rq_arg has + * already been decoded. Upon return, xdr->p points to the + * location of the upper layer header. */ static inline void svcxdr_init_decode(struct svc_rqst *rqstp) { struct xdr_stream *xdr = &rqstp->rq_arg_stream; - struct kvec *argv = rqstp->rq_arg.head; + struct xdr_buf *buf = &rqstp->rq_arg; + struct kvec *argv = buf->head;
- xdr_init_decode(xdr, &rqstp->rq_arg, argv->iov_base, NULL); + /* + * svc_getnl() and friends do not keep the xdr_buf's ::len + * field up to date. Refresh that field before initializing + * the argument decoding stream. + */ + buf->len = buf->head->iov_len + buf->page_len + buf->tail->iov_len; + + xdr_init_decode(xdr, buf, argv->iov_base, NULL); xdr_set_scratch_page(xdr, rqstp->rq_scratch_page); }