Subject: Re: [PATCH 1/2] uio_hv_generic: Fix a memory leak in error handling
paths

Cc Long Li.

Long, Stephen suggested I check with you. Do you have any opinion?

Wei.

On Tue, May 11, 2021 at 09:52:27AM +0000, Wei Liu wrote:

quoted

On Sun, May 09, 2021 at 09:13:03AM +0200, Christophe JAILLET wrote:

quoted

If 'vmbus_establish_gpadl()' fails, the (recv|send)_gpadl will not
be updated and 'hv_uio_cleanup()' in the error handling path will
not be able to free the corresponding buffer.

In such a case, we need to free the buffer explicitly.

Fixes: cdfa835c6e5e ("uio_hv_generic: defer opening vmbus until
first use")
Signed-off-by: Christophe JAILLET <redacted>
---
Before commit cdfa835c6e5e, the 'vfree' were done unconditionally in
'hv_uio_cleanup()'.
So, another way for fixing the potential leak is to modify
'hv_uio_cleanup()' and revert to the previous behavior.

I think this is cleaner.

Christophe has mentioned that the patch is already picked up by Greg KH.

I think both approaches are correct. We can go with this one.

quoted

Stephen, you authored cdfa835c6e5e. What do you think?

Christophe, OOI how did you discover these issues?

quoted

I don't know the underlying reason for this change so I don't know
which is the best way to fix this error handling path. Unless there
is a specific reason, changing 'hv_uio_cleanup()' could be better
because it would keep the error handling path of the probe cleaner,

IMHO.

quoted

quoted

---
 drivers/uio/uio_hv_generic.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/uio/uio_hv_generic.c

b/drivers/uio/uio_hv_generic.c index 0330ba99730e..eebc399f2cc7
100644

--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c

@@ -296,8 +296,10 @@ hv_uio_probe(struct hv_device *dev,

 	ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
 				    RECV_BUFFER_SIZE, &pdata->recv_gpadl);
-	if (ret)
+	if (ret) {
+		vfree(pdata->recv_buf);
 		goto fail_close;
+	}

 	/* put Global Physical Address Label in name */
 	snprintf(pdata->recv_name, sizeof(pdata->recv_name), @@ -316,8
+318,10 @@ hv_uio_probe(struct hv_device *dev,

 	ret = vmbus_establish_gpadl(channel, pdata->send_buf,
 				    SEND_BUFFER_SIZE, &pdata->send_gpadl);
-	if (ret)
+	if (ret) {
+		vfree(pdata->send_buf);
 		goto fail_close;
+	}

 	snprintf(pdata->send_name, sizeof(pdata->send_name),
 		 "send:%u", pdata->send_gpadl);
--

2.30.2