Re: [PATCH] KEYS: trusted: fix a couple error pointer dereferences

[Sumit Garg <sumit.garg@xxxxxxxxxx>]

Hi Serge,

On Wed, 14 Apr 2021 at 19:37, Serge E. Hallyn <serge@xxxxxxxxxx> wrote:
>
> On Wed, Apr 14, 2021 at 09:08:58AM +0300, Dan Carpenter wrote:
> > If registering "reg_shm_out" fails, then it is an error pointer and the
> > error handling will call tee_shm_free(reg_shm_out) which leads to an
> > error pointer dereference and an Oops.
> >
> > I've re-arranged it so we only free things that have been allocated
> > successfully.
> >
> > Fixes: 6dd95e650c8a ("KEYS: trusted: Introduce TEE based Trusted Keys")
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > ---
> >  security/keys/trusted-keys/trusted_tee.c | 24 ++++++++++--------------
> >  1 file changed, 10 insertions(+), 14 deletions(-)
> >
> > diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c
> > index 2ce66c199e1d..45f96f6ed673 100644
> > --- a/security/keys/trusted-keys/trusted_tee.c
> > +++ b/security/keys/trusted-keys/trusted_tee.c
> > @@ -65,7 +65,7 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
> >       int ret;
> >       struct tee_ioctl_invoke_arg inv_arg;
> >       struct tee_param param[4];
> > -     struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> > +     struct tee_shm *reg_shm_in, *reg_shm_out;
>
> I don't have this file (trusted_tee.c) in my tree and there's no lore
> link here to previous what threads this depends on.  Based on the
> context I can't verify that reg_shm_in will always be initialized
> before you get to the free_shm_in label.
>

You can find trusted_tee.c here [1].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/tree/security/keys/trusted-keys/trusted_tee.c

-Sumit

> >
> >       memset(&inv_arg, 0, sizeof(inv_arg));
> >       memset(&param, 0, sizeof(param));
> > @@ -84,7 +84,7 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
> >       if (IS_ERR(reg_shm_out)) {
> >               dev_err(pvt_data.dev, "blob shm register failed\n");
> >               ret = PTR_ERR(reg_shm_out);
> > -             goto out;
> > +             goto free_shm_in;
> >       }
> >
> >       inv_arg.func = TA_CMD_SEAL;
> > @@ -109,11 +109,9 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
> >               p->blob_len = param[1].u.memref.size;
> >       }
> >
> > -out:
> > -     if (reg_shm_out)
> > -             tee_shm_free(reg_shm_out);
> > -     if (reg_shm_in)
> > -             tee_shm_free(reg_shm_in);
> > +     tee_shm_free(reg_shm_out);
> > +free_shm_in:
> > +     tee_shm_free(reg_shm_in);
> >
> >       return ret;
> >  }
> > @@ -126,7 +124,7 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
> >       int ret;
> >       struct tee_ioctl_invoke_arg inv_arg;
> >       struct tee_param param[4];
> > -     struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
> > +     struct tee_shm *reg_shm_in, *reg_shm_out;
> >
> >       memset(&inv_arg, 0, sizeof(inv_arg));
> >       memset(&param, 0, sizeof(param));
> > @@ -145,7 +143,7 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
> >       if (IS_ERR(reg_shm_out)) {
> >               dev_err(pvt_data.dev, "key shm register failed\n");
> >               ret = PTR_ERR(reg_shm_out);
> > -             goto out;
> > +             goto free_shm_in;
> >       }
> >
> >       inv_arg.func = TA_CMD_UNSEAL;
> > @@ -170,11 +168,9 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
> >               p->key_len = param[1].u.memref.size;
> >       }
> >
> > -out:
> > -     if (reg_shm_out)
> > -             tee_shm_free(reg_shm_out);
> > -     if (reg_shm_in)
> > -             tee_shm_free(reg_shm_in);
> > +     tee_shm_free(reg_shm_out);
> > +free_shm_in:
> > +     tee_shm_free(reg_shm_in);
> >
> >       return ret;
> >  }
> > --
> > 2.30.2