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SubjectRE: [PATCH] qla4xxx: Return -ENOMEM on memory allocation failure


On Fri, 4 Jul 2014, Elliott, Robert (Server Storage) wrote:

>
>
> > -----Original Message-----
> > From: linux-scsi-owner@vger.kernel.org [mailto:linux-scsi-
> > owner@vger.kernel.org] On Behalf Of Himangi Saraogi
> > Sent: Friday, 04 July, 2014 1:28 PM
> > To: Vikas Chaudhary; iscsi-driver@qlogic.com; James E.J. Bottomley; linux-
> > scsi@vger.kernel.org; linux-kernel@vger.kernel.org
> > Cc: julia.lawall@lip6.fr
> > Subject: [PATCH] qla4xxx: Return -ENOMEM on memory allocation failure
> >
> > In this code, 0 is returned on memory allocation failure, even though
> > other failures return -ENOMEM or other similar values.
> >
> > A simplified version of the Coccinelle semantic match that finds this
> > problem is as follows:
> >
> > // <smpl>
> > @@
> > expression ret;
> > expression x,e1,e2,e3;
> > identifier alloc;
> > @@
> >
> > ret = 0
> > ... when != ret = e1
> > *x = alloc(...)
> > ... when != ret = e2
> > if (x == NULL) { ... when != ret = e3
> > return ret;
> > }
> > // </smpl>
> >
> > Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
> > Acked-by: Julia Lawall <julia.lawall@lip6.fr>
> > ---
> > drivers/scsi/qla4xxx/ql4_os.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/scsi/qla4xxx/ql4_os.c b/drivers/scsi/qla4xxx/ql4_os.c
> > index c5d9564..72ba671 100644
> > --- a/drivers/scsi/qla4xxx/ql4_os.c
> > +++ b/drivers/scsi/qla4xxx/ql4_os.c
> > @@ -1050,6 +1050,7 @@ static int qla4xxx_get_host_stats(struct Scsi_Host
> > *shost, char *buf, int len)
> > if (!ql_iscsi_stats) {
> > ql4_printk(KERN_ERR, ha,
> > "Unable to allocate memory for iscsi stats\n");
> > + ret = -ENOMEM;
> > goto exit_host_stats;
> > }
> >
>
> Also, the only caller of this function doesn't use the return
> value - it's overwritten by another function call:
>
> drivers/scsi/scsi_transport_iscsi.c:
> err = transport->get_host_stats(shost, buf, host_stats_size);
>
> actual_size = nlmsg_total_size(sizeof(*ev) + host_stats_size);
> skb_trim(skbhost_stats, NLMSG_ALIGN(actual_size));
> nlhhost_stats->nlmsg_len = actual_size;
>
> err = iscsi_multicast_skb(skbhost_stats, ISCSI_NL_GRP_ISCSID,
> GFP_KERNEL);

Maybe that is intentional? If get_host_stats fails, eg because of a lack
of memory, the worst that will happen is that a region of the buffer will
be 0. If the loop is done again, there seems to be a risk of an infinite
loop.

julia


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