linux-kernel - Re: [PATCH] xen/blkback: fix memory leaks

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Date:   Mon, 12 Aug 2019 10:49:11 +0200
From:   Roger Pau Monné <roger.pau@...rix.com>
To:     Wenwen Wang <wenwen@...uga.edu>
CC:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jens Axboe <axboe@...nel.dk>,
        "moderated list:XEN BLOCK SUBSYSTEM" <xen-devel@...ts.xenproject.org>,
        "open list:BLOCK LAYER" <linux-block@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xen/blkback: fix memory leaks

On Sun, Aug 11, 2019 at 12:23:22PM -0500, Wenwen Wang wrote:
> In read_per_ring_refs(), after 'req' and related memory regions are
> allocated, xen_blkif_map() is invoked to map the shared frame, irq, and
> etc. However, if this mapping process fails, no cleanup is performed,
> leading to memory leaks. To fix this issue, invoke the cleanup before
> returning the error.
> 
> Signed-off-by: Wenwen Wang <wenwen@...uga.edu>

Thanks!

> ---
>  drivers/block/xen-blkback/xenbus.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index 3ac6a5d..b90dbcd 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -965,6 +965,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
>  		}
>  	}
>  
> +	err = -ENOMEM;
>  	for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
>  		req = kzalloc(sizeof(*req), GFP_KERNEL);
>  		if (!req)
> @@ -987,7 +988,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
>  	err = xen_blkif_map(ring, ring_ref, nr_grefs, evtchn);

You could also move the xen_blkif_map cal before the allocation loop,
since there's nothing in xen_blkif_map that uses the memory allocated
AFAICT, but I'm fine either way.

Acked-by: Roger Pau Monné <roger.pau@...rix.com>

Roger.