[PATCH v4 2/5] cmd: optee_rpmb: close tee session
Igor Opaniuk
igor.opaniuk at gmail.com
Thu Apr 4 13:40:01 CEST 2024
Ilias,
On Thu, Apr 4, 2024 at 1:00 PM Ilias Apalodimas <ilias.apalodimas at linaro.org>
wrote:
> Hi Igor,
>
> On Thu, 4 Apr 2024 at 13:18, Igor Opaniuk <igor.opaniuk at gmail.com> wrote:
> >
> > Hi Ilias,
> >
> > On Thu, Apr 4, 2024 at 10:54 AM Ilias Apalodimas <
> ilias.apalodimas at linaro.org> wrote:
> >>
> >> Hi Igor,
> >>
> >> On Thu, 4 Apr 2024 at 11:40, Ilias Apalodimas
> >> <ilias.apalodimas at linaro.org> wrote:
> >> >
> >> > Hi Igor,
> >> >
> >> > I was about to apply the series, but noticed neither me or Jens were
> cc'ed
> >> > on this. Adding Jens to the party
> >> >
> >> > On Thu, Apr 04, 2024 at 10:13:49AM +0200, Igor Opaniuk wrote:
> >> > > Add calls for closing tee session after every read/write operation.
> >> >
> >> > What the patch is pretty obvious, but I am missing an explanation of
> why
> >> > this is needed
> >> >
> >> > >
> >> > > Signed-off-by: Igor Opaniuk <igor.opaniuk at gmail.com>
> >> > > ---
> >> > >
> >> > > (no changes since v1)
> >> > >
> >> > > cmd/optee_rpmb.c | 23 +++++++++++++++++------
> >> > > 1 file changed, 17 insertions(+), 6 deletions(-)
> >> > >
> >> > > diff --git a/cmd/optee_rpmb.c b/cmd/optee_rpmb.c
> >> > > index e0e44bbed04..b3cafd92410 100644
> >> > > --- a/cmd/optee_rpmb.c
> >> > > +++ b/cmd/optee_rpmb.c
> >> > > @@ -87,8 +87,10 @@ static int read_persistent_value(const char
> *name,
> >> > >
> >> > > rc = tee_shm_alloc(tee, name_size,
> >> > > TEE_SHM_ALLOC, &shm_name);
> >> > > - if (rc)
> >> > > - return -ENOMEM;
> >> > > + if (rc) {
> >> > > + rc = -ENOMEM;
> >> > > + goto close_session;
> >> > > + }
> >> >
> >> > I don't think you need the session to be opened to allocate memory.
> >> > So instead of of doing this, why don't we just move the alloc call
> before
> >> > opening the session?
> >>
> >> Looking at it again, we do need tee != NULL, but I think it's cleaner
> >> to add something like
> >> if (!dev)
> >> return -ENODEV
> >> to __tee_shm_add() instead.
> >
> > Do you mind if I address that in a separate patch series, as tbh I
> > don't want to add additional patches to the existing series?
>
> We still completely change the functionality. So, the patchset is not
> a 'tiny cleanup', it instead closes the session every time instead of
> keeping it open.
> There are a few things going on, that aren't explained clearly in the
> commit message
> - Why is this needed? Looking at the code it is an actual problem
> since sessions tied to the AVB uuid will remain open
> - Is there any side effect by always closing the session?
> I don't mind merging it as is with a proper commit message, but I
> think the alternative is just easier.
>
I'll provide a bit more context here. The problem initially was in the TEE
sandbox
driver implementation(drivers/tee/sandbox.c) and it's limitations, which
doesn't
permit to have multiple simultaneous sessions with different TAs.
This is what actually happened in this CI run [1], firstly "optee_rpmb"
cmd was executed (and after execution we had one session open), and
then "scp03", which also makes calls to OP-TEE, however it fails
in sandbox_tee_open_session() because of this check:
if (state->ta) {
printf("A session is already open\n");
return -EBUSY;
}
So basically I had two ways in mind to address that:
1. Close a session on each optee_rpmb cmd invocation.
I don't see any reason to keep this session open, as obviously
there is no other mechanism (tbh, I don't know if DM calls ".remove" for
active
devices) to close it automatically before handing over control to
Linux kernel. As a result we might end up with some orphaned sessions
registered in OP-TEE OS core (obvious resource leak).
2. Extend TEE sandbox driver, add support for multiple
simultaneous sessions just to handle the case.
I've chosen the first approach, as IMO it was "kill two birds with one
stone",
I could address resource leak in OP-TEE and bypass limitations of
TEE sandbox driver.
[1] https://source.denx.de/u-boot/custodians/u-boot-tpm/-/jobs/792216
>
> Thanks
> /Ilias
>
> >
> >>
> >>
> >> Cheers
> >> /Ilias
> >> >
> >> > >
> >> > > rc = tee_shm_alloc(tee, buffer_size,
> >> > > TEE_SHM_ALLOC, &shm_buf);
> >> > > @@ -125,6 +127,9 @@ out:
> >> > > tee_shm_free(shm_buf);
> >> > > free_name:
> >> > > tee_shm_free(shm_name);
> >> > > +close_session:
> >> > > + tee_close_session(tee, session);
> >> > > + tee = NULL;
> >> > >
> >> > > return rc;
> >> > > }
> >> > > @@ -139,17 +144,20 @@ static int write_persistent_value(const char
> *name,
> >> > > struct tee_param param[2];
> >> > > size_t name_size = strlen(name) + 1;
> >> > >
> >> > > + if (!value_size)
> >> > > + return -EINVAL;
> >> > > +
> >> > > if (!tee) {
> >> > > if (avb_ta_open_session())
> >> > > return -ENODEV;
> >> > > }
> >> > > - if (!value_size)
> >> > > - return -EINVAL;
> >> > >
> >> > > rc = tee_shm_alloc(tee, name_size,
> >> > > TEE_SHM_ALLOC, &shm_name);
> >> > > - if (rc)
> >> > > - return -ENOMEM;
> >> > > + if (rc) {
> >> > > + rc = -ENOMEM;
> >> > > + goto close_session;
> >> > > + }
> >> >
> >> > ditto
> >> >
> >> > >
> >> > > rc = tee_shm_alloc(tee, value_size,
> >> > > TEE_SHM_ALLOC, &shm_buf);
> >> > > @@ -178,6 +186,9 @@ out:
> >> > > tee_shm_free(shm_buf);
> >> > > free_name:
> >> > > tee_shm_free(shm_name);
> >> > > +close_session:
> >> > > + tee_close_session(tee, session);
> >> > > + tee = NULL;
> >> > >
> >> > > return rc;
> >> > > }
> >> > > --
> >> > > 2.34.1
> >> > >
> >> >
> >> > Thanks
> >> > /Ilias
> >
> >
> >
> >
> > --
> > Best regards - Atentamente - Meilleures salutations
> >
> > Igor Opaniuk
> >
> > mailto: igor.opaniuk at gmail.com
> > skype: igor.opanyuk
> > https://www.linkedin.com/in/iopaniuk
>
--
Best regards - Atentamente - Meilleures salutations
Igor Opaniuk
mailto: igor.opaniuk at gmail.com
skype: igor.opanyuk
https://www.linkedin.com/in/iopaniuk <http://ua.linkedin.com/in/iopaniuk>
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