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    SubjectRe: [PATCH] drivers/block/drbd: add NULL test around call to crypto_free_hash


    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/)
    >
    > // <smpl>
    > @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)
    > // </smpl>
    >
    > Signed-off-by: Julia Lawall <julia@diku.dk>
    >
    > ---
    > 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.

    just my 2 cents,
    re,
    wh




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