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

From: Sumit Garg
Date: Wed Aug 23 2023 - 02:55:55 EST

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).

-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
> >