From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756245Ab1AaRpE (ORCPT ); Mon, 31 Jan 2011 12:45:04 -0500 Received: from mgw2.diku.dk ([130.225.96.92]:55248 "EHLO mgw2.diku.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756141Ab1AaRpA (ORCPT ); Mon, 31 Jan 2011 12:45:00 -0500 Date: Mon, 31 Jan 2011 18:44:54 +0100 (CET) From: Julia Lawall To: walter harms Cc: Lars Ellenberg , kernel-janitors@vger.kernel.org, drbd-user@lists.linbit.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers/block/drbd: add NULL test around call to crypto_free_hash In-Reply-To: <4D46F3E5.7060804@bfs.de> Message-ID: References: <1296496263-16362-1-git-send-email-julia@diku.dk> <4D46F3E5.7060804@bfs.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 31 Jan 2011, walter harms wrote: > > > Am 31.01.2011 18:51, schrieb Julia Lawall: > > crypto_free_hash calls the function crypto_hash_tfm and then > > crypto_free_tfm on the result. crypto_free_tfm calls crypto_destroy_tfm, > > which tests this result for NULL and then dereferences it. crypto_hash_tfm > > returns &tfm->base where tfm is its argument. base is actually the first > > and only field of a crypto_hash-typed structure, so perhaps one can rely on > > it to return NULL for a NULL value of tfm. But most calls to > > crypto_hash_tfm where the argument might be NULL don't rely on this > > property and test for NULL explicitly. > > > > The semantic match that finds this problem is as follows: > > (http://coccinelle.lip6.fr/) > > > > // > > @safe@ > > position p; > > expression x; > > @@ > > > > if (x) { <+... crypto_free_hash@p(x) ...+> } > > > > @@ > > expression x; > > position p!=safe.p; > > @@ > > > > *x = NULL > > ... > > *crypto_free_hash@p(x) > > // > > > > Signed-off-by: Julia Lawall > > > > --- > > drivers/block/drbd/drbd_nl.c | 18 ++++++++++++------ > > drivers/block/drbd/drbd_receiver.c | 6 ++++-- > > 2 files changed, 16 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c > > index 8cbfaa6..aa5fbc0 100644 > > --- a/drivers/block/drbd/drbd_nl.c > > +++ b/drivers/block/drbd/drbd_nl.c > > @@ -1482,13 +1482,16 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp, > > mdev->ee_hash = new_ee_hash; > > } > > > > - crypto_free_hash(mdev->cram_hmac_tfm); > > + if (mdev->cram_hmac_tfm) > > + crypto_free_hash(mdev->cram_hmac_tfm); > > mdev->cram_hmac_tfm = tfm; > > > > - crypto_free_hash(mdev->integrity_w_tfm); > > + if (mdev->integrity_w_tfm) > > + crypto_free_hash(mdev->integrity_w_tfm); > > mdev->integrity_w_tfm = integrity_w_tfm; > > > > - crypto_free_hash(mdev->integrity_r_tfm); > > + if (mdev->integrity_r_tfm) > > + crypto_free_hash(mdev->integrity_r_tfm); > > mdev->integrity_r_tfm = integrity_r_tfm; > > > > kfree(mdev->int_dig_out); > > @@ -1509,9 +1512,12 @@ fail: > > kfree(int_dig_out); > > kfree(int_dig_in); > > kfree(int_dig_vv); > > - crypto_free_hash(tfm); > > - crypto_free_hash(integrity_w_tfm); > > - crypto_free_hash(integrity_r_tfm); > > + if (tfm) > > + crypto_free_hash(tfm); > > + if (integrity_w_tfm) > > + crypto_free_hash(integrity_w_tfm); > > + if (integrity_r_tfm) > > + crypto_free_hash(integrity_r_tfm); > > kfree(new_tl_hash); > > kfree(new_ee_hash); > > kfree(new_conf); > > diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c > > index 24487d4..3453cc3 100644 > > --- a/drivers/block/drbd/drbd_receiver.c > > +++ b/drivers/block/drbd/drbd_receiver.c > > @@ -2871,9 +2871,11 @@ static int receive_SyncParam(struct drbd_conf *mdev, enum drbd_packets cmd, unsi > > disconnect: > > /* just for completeness: actually not needed, > > * as this is not reached if csums_tfm was ok. */ > > - crypto_free_hash(csums_tfm); > > + if (csums_tfm) > > + crypto_free_hash(csums_tfm); > > /* but free the verify_tfm again, if csums_tfm did not work out */ > > - crypto_free_hash(verify_tfm); > > + if (verify_tfm) > > + crypto_free_hash(verify_tfm); > > drbd_force_state(mdev, NS(conn, C_DISCONNECTING)); > > return FALSE; > > } > > > > it looks that it would be more sensibel to change crypto_free_hash() to handle > NULL that would be more consistent with the free() family. That was the other option... julia