[PATCH 5.15 026/123] 9p/xen: check logical size for buffer size

Greg Kroah-Hartman
2022-12-12T13:26:24Z

From: Dominique Martinet <asmadeus@codewreck.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@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>
Signed-off-by: Sasha Levin <sashal@kernel.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 427f6caefa29..4255f2a3bea4 100644
--- a/net/9p/trans_xen.c
+++ b/net/9p/trans_xen.c
@@ -231,6 +231,14 @@ 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;

@@ -240,6 +248,7 @@ 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