[PATCH] ceph: don't reference req after put

[PATCH] ceph: don't reference req after put

[Alex Elder]

In __unregister_request(), there is a call to list_del_init()
referencing a request that was the subject of a call to
ceph_osdc_put_request() on the previous line.  This is not
safe, because the request structure could have been freed
by the time we reach the list_del_init().

Fix this by reversing the order of these lines.

Signed-off-by: Alex Elder <elder@inktank.com>
---
 net/ceph/osd_client.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 9b6f0e4..d1177ec 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -797,9 +797,9 @@ static void __unregister_request(struct
ceph_osd_client *osdc,
 			req->r_osd = NULL;
 	}

+	list_del_init(&req->r_req_lru_item);
 	ceph_osdc_put_request(req);

-	list_del_init(&req->r_req_lru_item);
 	if (osdc->num_requests == 0) {
 		dout(" no requests, canceling timeout\n");
 		__cancel_osd_timeout(osdc);
-- 
1.7.9.5

Re: [PATCH] ceph: don't reference req after put

[Sage Weil]

Reviewed-by: Sage Weil <sage@inktank.com>

On Thu, 29 Nov 2012, Alex Elder wrote:

> In __unregister_request(), there is a call to list_del_init()
> referencing a request that was the subject of a call to
> ceph_osdc_put_request() on the previous line.  This is not
> safe, because the request structure could have been freed
> by the time we reach the list_del_init().
> 
> Fix this by reversing the order of these lines.
> 
> Signed-off-by: Alex Elder <elder@inktank.com>
> ---
>  net/ceph/osd_client.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index 9b6f0e4..d1177ec 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -797,9 +797,9 @@ static void __unregister_request(struct
> ceph_osd_client *osdc,
>  			req->r_osd = NULL;
>  	}
> 
> +	list_del_init(&req->r_req_lru_item);
>  	ceph_osdc_put_request(req);
> 
> -	list_del_init(&req->r_req_lru_item);
>  	if (osdc->num_requests == 0) {
>  		dout(" no requests, canceling timeout\n");
>  		__cancel_osd_timeout(osdc);
> -- 
> 1.7.9.5
> 
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