Re: [PATCH] KEYS: trusted: tee: Refactor register SHM usage

From: Jens Wiklander
Date: Wed Aug 23 2023 - 04:03:54 EST

On Wed, Aug 23, 2023 at 8:55 AM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote:
>
> On Tue, 22 Aug 2023 at 18:25, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> >
> > On Tue, Aug 22, 2023 at 04:59:33PM +0530, Sumit Garg wrote:
> > > The OP-TEE driver using the old SMC based ABI permits overlapping shared
> > > buffers, but with the new FF-A based ABI each physical page may only
> > > be registered once.
> > >
> > > As the key and blob buffer are allocated adjancently, there is no need
> > > for redundant register shared memory invocation. Also, it is incompatibile
> > > with FF-A based ABI limitation. So refactor register shared memory
> > > implementation to use only single invocation to register both key and blob
> > > buffers.
> > >
> > > Fixes: 4615e5a34b95 ("optee: add FF-A support")
> > > Reported-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> > > Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> > > ---
> > > security/keys/trusted-keys/trusted_tee.c | 64 ++++++++----------------
> > > 1 file changed, 20 insertions(+), 44 deletions(-)
> > >
> > > diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c
> > > index ac3e270ade69..aa3d477de6db 100644
> > > --- a/security/keys/trusted-keys/trusted_tee.c
> > > +++ b/security/keys/trusted-keys/trusted_tee.c
> > > @@ -65,24 +65,16 @@ 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 = NULL;
> > >
> > > memset(&inv_arg, 0, sizeof(inv_arg));
> > > memset(&param, 0, sizeof(param));
> > >
> > > - reg_shm_in = tee_shm_register_kernel_buf(pvt_data.ctx, p->key,
> > > - p->key_len);
> > > - if (IS_ERR(reg_shm_in)) {
> > > - dev_err(pvt_data.dev, "key shm register failed\n");
> > > - return PTR_ERR(reg_shm_in);
> > > - }
> > > -
> > > - reg_shm_out = tee_shm_register_kernel_buf(pvt_data.ctx, p->blob,
> > > - sizeof(p->blob));
> > > - if (IS_ERR(reg_shm_out)) {
> > > - dev_err(pvt_data.dev, "blob shm register failed\n");
> > > - ret = PTR_ERR(reg_shm_out);
> > > - goto out;
> > > + reg_shm = tee_shm_register_kernel_buf(pvt_data.ctx, p->key,
> > > + sizeof(p->key) + sizeof(p->blob));
> >
> > This is somewhat fragile. What if struct trusted_key_payload has a small
> > unexpected change in layout?
>
> key and blob buffers are just two adjacent fixed sized byte arrays. So
> I am not worried here as long as they stay adjacent (which has been
> the case since trusted keys were introduced in the kernel).

Yeah, that was my point, but fine if you don't believe it's an issue.

Thanks,
Jens

>
> -Sumit
>
> >
> > Thanks,
> > Jens
> >
> > > + if (IS_ERR(reg_shm)) {
> > > + dev_err(pvt_data.dev, "shm register failed\n");
> > > + return PTR_ERR(reg_shm);
> > > }
> > >
> > > inv_arg.func = TA_CMD_SEAL;
> > > @@ -90,13 +82,13 @@ static int trusted_tee_seal(struct trusted_key_payload *p, char *datablob)
> > > inv_arg.num_params = 4;
> > >
> > > param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
> > > - param[0].u.memref.shm = reg_shm_in;
> > > + param[0].u.memref.shm = reg_shm;
> > > param[0].u.memref.size = p->key_len;
> > > param[0].u.memref.shm_offs = 0;
> > > param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> > > - param[1].u.memref.shm = reg_shm_out;
> > > + param[1].u.memref.shm = reg_shm;
> > > param[1].u.memref.size = sizeof(p->blob);
> > > - param[1].u.memref.shm_offs = 0;
> > > + param[1].u.memref.shm_offs = sizeof(p->key);
> > >
> > > ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
> > > if ((ret < 0) || (inv_arg.ret != 0)) {
> > > @@ -107,11 +99,7 @@ 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);
> > >
> > > return ret;
> > > }
> > > @@ -124,24 +112,16 @@ 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 = NULL;
> > >
> > > memset(&inv_arg, 0, sizeof(inv_arg));
> > > memset(&param, 0, sizeof(param));
> > >
> > > - reg_shm_in = tee_shm_register_kernel_buf(pvt_data.ctx, p->blob,
> > > - p->blob_len);
> > > - if (IS_ERR(reg_shm_in)) {
> > > - dev_err(pvt_data.dev, "blob shm register failed\n");
> > > - return PTR_ERR(reg_shm_in);
> > > - }
> > > -
> > > - reg_shm_out = tee_shm_register_kernel_buf(pvt_data.ctx, p->key,
> > > - sizeof(p->key));
> > > - if (IS_ERR(reg_shm_out)) {
> > > - dev_err(pvt_data.dev, "key shm register failed\n");
> > > - ret = PTR_ERR(reg_shm_out);
> > > - goto out;
> > > + reg_shm = tee_shm_register_kernel_buf(pvt_data.ctx, p->key,
> > > + sizeof(p->key) + sizeof(p->blob));
> > > + if (IS_ERR(reg_shm)) {
> > > + dev_err(pvt_data.dev, "shm register failed\n");
> > > + return PTR_ERR(reg_shm);
> > > }
> > >
> > > inv_arg.func = TA_CMD_UNSEAL;
> > > @@ -149,11 +129,11 @@ static int trusted_tee_unseal(struct trusted_key_payload *p, char *datablob)
> > > inv_arg.num_params = 4;
> > >
> > > param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
> > > - param[0].u.memref.shm = reg_shm_in;
> > > + param[0].u.memref.shm = reg_shm;
> > > param[0].u.memref.size = p->blob_len;
> > > - param[0].u.memref.shm_offs = 0;
> > > + param[0].u.memref.shm_offs = sizeof(p->key);
> > > param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
> > > - param[1].u.memref.shm = reg_shm_out;
> > > + param[1].u.memref.shm = reg_shm;
> > > param[1].u.memref.size = sizeof(p->key);
> > > param[1].u.memref.shm_offs = 0;
> > >
> > > @@ -166,11 +146,7 @@ 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);
> > >
> > > return ret;
> > > }
> > > --
> > > 2.34.1
> > >