[PATCH 5.4 088/102] SUNRPC: Fix another issue with MIC buffer space

Greg Kroah-Hartman
2020-01-24T09:41:52Z

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

[ Upstream commit e8d70b321ecc9b23d09b8df63e38a2f73160c209 ]

xdr_shrink_pagelen() BUG's when @len is larger than buf->page_len.
This can happen when xdr_buf_read_mic() is given an xdr_buf with
a small page array (like, only a few bytes).

Instead, just cap the number of bytes that xdr_shrink_pagelen()
will move.

Fixes: 5f1bc39979d ("SUNRPC: Fix buffer handling of GSS MIC ... ")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sunrpc/xdr.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 14ba9e72a2049..f3104be8ff5dc 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -436,13 +436,12 @@ xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
}

/**
- * xdr_shrink_pagelen
+ * xdr_shrink_pagelen - shrinks buf->pages by up to @len bytes
* @buf: xdr_buf
* @len: bytes to remove from buf->pages
*
- * Shrinks XDR buffer's page array buf->pages by
- * 'len' bytes. The extra data is not lost, but is instead
- * moved into the tail.
+ * The extra data is not lost, but is instead moved into buf->tail.
+ * Returns the actual number of bytes moved.
*/
static unsigned int
xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
@@ -455,8 +454,8 @@ xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)

result = 0;
tail = buf->tail;
- BUG_ON (len > pglen);
-
+ if (len > buf->page_len)
+ len = buf-> page_len;
tailbuf_len = buf->buflen - buf->head->iov_len - buf->page_len;

/* Shift the tail first */
--
2.20.1