From: Dominique Martinet <asmadeus@codewreck.org>
Date: Fri, 18 Nov 2022 13:44:41 +0000 (+0900)
Subject: 9p/xen: check logical size for buffer size
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=391c18cf776eb4569ecda1f7794f360fe0a45a26;p=linux.git

9p/xen: check logical size for buffer size

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@kernel.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Link: https://lkml.kernel.org/r/20221118135542.63400-1-asmadeus@codewreck.org
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
---

diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
index b15c64128c3e5..aaa5fd364691b 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;