linux-kernel - [PATCH 5.4 171/178] SUNRPC: Properly set the @subbuf parameter of xdr_buf

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Message-Id: <20200629152523.2494198-172-sashal@kernel.org>
Date:   Mon, 29 Jun 2020 11:25:16 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Anna Schumaker <Anna.Schumaker@...app.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH 5.4 171/178] SUNRPC: Properly set the @subbuf parameter of xdr_buf_subsegment()

From: Chuck Lever <chuck.lever@...cle.com>

commit 89a3c9f5b9f0bcaa9aea3e8b2a616fcaea9aad78 upstream.

@subbuf is an output parameter of xdr_buf_subsegment(). A survey of
call sites shows that @subbuf is always uninitialized before
xdr_buf_segment() is invoked by callers.

There are some execution paths through xdr_buf_subsegment() that do
not set all of the fields in @subbuf, leaving some pointer fields
containing garbage addresses. Subsequent processing of that buffer
then results in a page fault.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Anna Schumaker <Anna.Schumaker@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sunrpc/xdr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 451ca7ec321c0..7ef37054071f8 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1118,6 +1118,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->head[0].iov_len;
+		subbuf->head[0].iov_base = buf->head[0].iov_base;
 		subbuf->head[0].iov_len = 0;
 	}
 
@@ -1130,6 +1131,8 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->page_len;
+		subbuf->pages = buf->pages;
+		subbuf->page_base = 0;
 		subbuf->page_len = 0;
 	}
 
@@ -1141,6 +1144,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->tail[0].iov_len;
+		subbuf->tail[0].iov_base = buf->tail[0].iov_base;
 		subbuf->tail[0].iov_len = 0;
 	}
 
-- 
2.25.1