Messages in this thread Patch in this message | | | From | Dominique Martinet <> | Subject | [PATCH 1/2] 9p/xen: check logical size for buffer size | Date | Fri, 18 Nov 2022 22:55:41 +0900 |
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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
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> ---
This comes more or less as a follow up of a fix for trans_fd: https://lkml.kernel.org/r/20221117091159.31533-1-guozihua@huawei.com Where msize should be replaced by capacity check, except trans_xen did not actually use to check the size fits at all.
While we normally trust the hypervisor (they can probably do whatever they want with our memory), a bug in the 9p server is always possible so sanity checks never hurt, especially now buffers got drastically smaller with a recent patch.
My setup for xen is unfortunately long dead so I cannot test this: Stefano, you've tested v9fs xen patches in the past, would you mind verifying this works as well?
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 b15c64128c3e..66ceb3b3ae30 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, rreq->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; -- 2.38.1
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