linux-kernel - [PATCH AUTOSEL 6.0 34/39] 9p/xen: check logical size for buffer size

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Message-Id: <20221128173642.1441232-34-sashal@kernel.org>
Date:   Mon, 28 Nov 2022 12:36:14 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dominique Martinet <asmadeus@...ewreck.org>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Christian Schoenebeck <linux_oss@...debyte.com>,
        Sasha Levin <sashal@...nel.org>, ericvh@...il.com,
        lucho@...kov.net, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com,
        v9fs-developer@...ts.sourceforge.net, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.0 34/39] 9p/xen: check logical size for buffer size

From: Dominique Martinet <asmadeus@...ewreck.org>

[ Upstream commit 391c18cf776eb4569ecda1f7794f360fe0a45a26 ]

trans_xen did not check the data fits into the buffer before copying
from the xen ring, but we probably should.
Add a check that just skips the request and return an error to
userspace if it did not fit

Tested-by: Stefano Stabellini <sstabellini@...nel.org>
Reviewed-by: Christian Schoenebeck <linux_oss@...debyte.com>
Link: https://lkml.kernel.org/r/20221118135542.63400-1-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/9p/trans_xen.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index 227f89cc7237..0f862d5a5960 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -208,6 +208,14 @@ static void p9_xen_response(struct work_struct *work)
 			continue;
 		}
 
+		if (h.size > req->rc.capacity) {
+			dev_warn(&priv->dev->dev,
+				 "requested packet size too big: %d for tag %d with capacity %zd\n",
+				 h.size, h.tag, req->rc.capacity);
+			req->status = REQ_STATUS_ERROR;
+			goto recv_error;
+		}
+
 		memcpy(&req->rc, &h, sizeof(h));
 		req->rc.offset = 0;
 
@@ -217,6 +225,7 @@ static void p9_xen_response(struct work_struct *work)
 				     masked_prod, &masked_cons,
 				     XEN_9PFS_RING_SIZE(ring));
 
+recv_error:
 		virt_mb();
 		cons += h.size;
 		ring->intf->in_cons = cons;
-- 
2.35.1