[PATCH] hwrng: core - Add WARN_ON for buggy read return values

[PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Herbert Xu]

Dear TPM maintainers:

Please have a look at the tpm hwrng driver because it appears to
be returning a length longer than the buffer length that we gave
it.  In particular, tpm2 appears to be the culprit (though I didn't
really check tpm1 at all so it could also be buggy).

The following patch hopefully should confirm that this is indeed
caused by TPM and not some other HWRNG driver.

---8<---
If a buggy driver returns a length that is longer than the size
of the buffer provided to it, then this may lead to a buffer overread
in the caller.

Stop this by adding a check for it in the hwrng core.

Reported-by: Guangwu Zhang <guazhang@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index 57c51efa5613..018316f54621 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -181,8 +181,15 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
 	int present;
 
 	BUG_ON(!mutex_is_locked(&reading_mutex));
-	if (rng->read)
-		return rng->read(rng, (void *)buffer, size, wait);
+	if (rng->read) {
+		int err;
+
+		err = rng->read(rng, buffer, size, wait);
+		if (WARN_ON_ONCE(err > 0 && err > size))
+			err = size;
+
+		return err;
+	}
 
 	if (rng->data_present)
 		present = rng->data_present(rng, wait);
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 9:05 AM EEST, Herbert Xu wrote:
> Dear TPM maintainers:

There's really only just me (for past 10 years). Maybe that should be
updatred.

>
> Please have a look at the tpm hwrng driver because it appears to
> be returning a length longer than the buffer length that we gave
> it.  In particular, tpm2 appears to be the culprit (though I didn't
> really check tpm1 at all so it could also be buggy).
>
> The following patch hopefully should confirm that this is indeed
> caused by TPM and not some other HWRNG driver.




>
> ---8<---
> If a buggy driver returns a length that is longer than the size
> of the buffer provided to it, then this may lead to a buffer overread
> in the caller.
>
> Stop this by adding a check for it in the hwrng core.
>
> Reported-by: Guangwu Zhang <guazhang@redhat.com>
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 57c51efa5613..018316f54621 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -181,8 +181,15 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
>  	int present;
>  
>  	BUG_ON(!mutex_is_locked(&reading_mutex));
> -	if (rng->read)
> -		return rng->read(rng, (void *)buffer, size, wait);
> +	if (rng->read) {
> +		int err;
> +
> +		err = rng->read(rng, buffer, size, wait);
> +		if (WARN_ON_ONCE(err > 0 && err > size))

Are you sure you want to use WARN_ON_ONCE here instead of
pr_warn_once()? I.e. is it worth of taking down the whole
kernel?

> +			err = size;
> +
> +		return err;
> +	}
>  
>  	if (rng->data_present)
>  		present = rng->data_present(rng, wait);

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 10:52 AM EEST, Jarkko Sakkinen wrote:
> On Mon Sep 23, 2024 at 9:05 AM EEST, Herbert Xu wrote:
> > Dear TPM maintainers:
>
> There's really only just me (for past 10 years). Maybe that should be
> updatred.
>
> >
> > Please have a look at the tpm hwrng driver because it appears to
> > be returning a length longer than the buffer length that we gave
> > it.  In particular, tpm2 appears to be the culprit (though I didn't
> > really check tpm1 at all so it could also be buggy).
> >
> > The following patch hopefully should confirm that this is indeed
> > caused by TPM and not some other HWRNG driver.
>
>
>
>
> >
> > ---8<---
> > If a buggy driver returns a length that is longer than the size
> > of the buffer provided to it, then this may lead to a buffer overread
> > in the caller.
> >
> > Stop this by adding a check for it in the hwrng core.
> >
> > Reported-by: Guangwu Zhang <guazhang@redhat.com>
> > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> >
> > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> > index 57c51efa5613..018316f54621 100644
> > --- a/drivers/char/hw_random/core.c
> > +++ b/drivers/char/hw_random/core.c
> > @@ -181,8 +181,15 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> >  	int present;
> >  
> >  	BUG_ON(!mutex_is_locked(&reading_mutex));
> > -	if (rng->read)
> > -		return rng->read(rng, (void *)buffer, size, wait);
> > +	if (rng->read) {
> > +		int err;
> > +
> > +		err = rng->read(rng, buffer, size, wait);
> > +		if (WARN_ON_ONCE(err > 0 && err > size))
>
> Are you sure you want to use WARN_ON_ONCE here instead of
> pr_warn_once()? I.e. is it worth of taking down the whole
> kernel?

I looked at tpm2_get_random() and it is pretty inefficient (not same
as saying it has a bug). I'd love to reimplement it.

We would be better of it would pull random let's say with 256 byte
or 512 byte chunks and cache that internal to tpm_chip. Then the
requests would be served from that pre-fetched pool and not do
round-trip to TPM every single time.

This would improve overall kernel performance given the reduced
number of wait states. I wonder if anyone knows what would be a
good fetch size that will work on most TPM2 chips?

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 11:07 AM EEST, Jarkko Sakkinen wrote:
> On Mon Sep 23, 2024 at 10:52 AM EEST, Jarkko Sakkinen wrote:
> > On Mon Sep 23, 2024 at 9:05 AM EEST, Herbert Xu wrote:
> > > Dear TPM maintainers:
> >
> > There's really only just me (for past 10 years). Maybe that should be
> > updatred.
> >
> > >
> > > Please have a look at the tpm hwrng driver because it appears to
> > > be returning a length longer than the buffer length that we gave
> > > it.  In particular, tpm2 appears to be the culprit (though I didn't
> > > really check tpm1 at all so it could also be buggy).
> > >
> > > The following patch hopefully should confirm that this is indeed
> > > caused by TPM and not some other HWRNG driver.
> >
> >
> >
> >
> > >
> > > ---8<---
> > > If a buggy driver returns a length that is longer than the size
> > > of the buffer provided to it, then this may lead to a buffer overread
> > > in the caller.
> > >
> > > Stop this by adding a check for it in the hwrng core.
> > >
> > > Reported-by: Guangwu Zhang <guazhang@redhat.com>
> > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> > >
> > > diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> > > index 57c51efa5613..018316f54621 100644
> > > --- a/drivers/char/hw_random/core.c
> > > +++ b/drivers/char/hw_random/core.c
> > > @@ -181,8 +181,15 @@ static inline int rng_get_data(struct hwrng *rng, u8 *buffer, size_t size,
> > >  	int present;
> > >  
> > >  	BUG_ON(!mutex_is_locked(&reading_mutex));
> > > -	if (rng->read)
> > > -		return rng->read(rng, (void *)buffer, size, wait);
> > > +	if (rng->read) {
> > > +		int err;
> > > +
> > > +		err = rng->read(rng, buffer, size, wait);
> > > +		if (WARN_ON_ONCE(err > 0 && err > size))
> >
> > Are you sure you want to use WARN_ON_ONCE here instead of
> > pr_warn_once()? I.e. is it worth of taking down the whole
> > kernel?
>
> I looked at tpm2_get_random() and it is pretty inefficient (not same
> as saying it has a bug). I'd love to reimplement it.
>
> We would be better of it would pull random let's say with 256 byte
> or 512 byte chunks and cache that internal to tpm_chip. Then the
> requests would be served from that pre-fetched pool and not do
> round-trip to TPM every single time.
>
> This would improve overall kernel performance given the reduced
> number of wait states. I wonder if anyone knows what would be a
> good fetch size that will work on most TPM2 chips?

Herbert, I'm going to go to gym but I could help you to debug the
issue you're seeing with a patch from tpm2_get_random(). We need
to fix that one first ofc (as you never should build on top of
broken code). Once back from gym and grocery shopping I'll bake
a debugging patch.

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Herbert Xu]

On Mon, Sep 23, 2024 at 10:52:49AM +0300, Jarkko Sakkinen wrote:
> On Mon Sep 23, 2024 at 9:05 AM EEST, Herbert Xu wrote:
> > Dear TPM maintainers:
> 
> There's really only just me (for past 10 years). Maybe that should be
> updatred.

:)

> >  	BUG_ON(!mutex_is_locked(&reading_mutex));
> > -	if (rng->read)
> > -		return rng->read(rng, (void *)buffer, size, wait);
> > +	if (rng->read) {
> > +		int err;
> > +
> > +		err = rng->read(rng, buffer, size, wait);
> > +		if (WARN_ON_ONCE(err > 0 && err > size))
> 
> Are you sure you want to use WARN_ON_ONCE here instead of
> pr_warn_once()? I.e. is it worth of taking down the whole
> kernel?

Absolutely.  If this triggers it's a serious kernel bug and we
should gather as much information as possible.  pr_warn_once is
not the same thing as WARN_ON_ONCE in terms of what it prints.

If people want to turn WARNs into BUGs, then they've only got
themselves to blame when the kernel goes down.  On the other
hand perhaps they *do* want this to panic and we should hand
it to them.

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 12:26 PM EEST, Herbert Xu wrote:
 > > +
> > > +		err = rng->read(rng, buffer, size, wait);
> > > +		if (WARN_ON_ONCE(err > 0 && err > size))
> > 
> > Are you sure you want to use WARN_ON_ONCE here instead of
> > pr_warn_once()? I.e. is it worth of taking down the whole
> > kernel?
>
> Absolutely.  If this triggers it's a serious kernel bug and we
> should gather as much information as possible.  pr_warn_once is
> not the same thing as WARN_ON_ONCE in terms of what it prints.

Personally I allow the use of WARN only as the last resort.

If you need stack printout you can always use dump_stack().

>
> If people want to turn WARNs into BUGs, then they've only got
> themselves to blame when the kernel goes down.  On the other
> hand perhaps they *do* want this to panic and we should hand
> it to them.

Actually when you turn on "panic_on_warn" the user expectation is and
should be that the sites where WARN is used have been hand picked with
consideration so that panic happens for a reason.

This has also been denoted repeatedly by Greg:

https://lore.kernel.org/linux-cve-announce/2024061828-CVE-2024-36975-6719@gregkh/

I should check this somewhere but actually these days a wrongly chosen
WARN() might lead to CVE entry. That fix was by me but I never created
the CVE.

Greg, did we have something under Documentation/ that would fully
address the use of WARN?

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 5:31 PM EEST, Jarkko Sakkinen wrote:
> Greg, did we have something under Documentation/ that would fully
> address the use of WARN?

... personally I think that even if there was a separate document, this
should be somehow addressed already in SubmittingPatches so that it
can't be possibly missed by anyone.

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Greg KH]

On Mon, Sep 23, 2024 at 05:31:47PM +0300, Jarkko Sakkinen wrote:
> On Mon Sep 23, 2024 at 12:26 PM EEST, Herbert Xu wrote:
>  > > +
> > > > +		err = rng->read(rng, buffer, size, wait);
> > > > +		if (WARN_ON_ONCE(err > 0 && err > size))
> > > 
> > > Are you sure you want to use WARN_ON_ONCE here instead of
> > > pr_warn_once()? I.e. is it worth of taking down the whole
> > > kernel?
> >
> > Absolutely.  If this triggers it's a serious kernel bug and we
> > should gather as much information as possible.  pr_warn_once is
> > not the same thing as WARN_ON_ONCE in terms of what it prints.
> 
> Personally I allow the use of WARN only as the last resort.
> 
> If you need stack printout you can always use dump_stack().
> 
> >
> > If people want to turn WARNs into BUGs, then they've only got
> > themselves to blame when the kernel goes down.  On the other
> > hand perhaps they *do* want this to panic and we should hand
> > it to them.
> 
> Actually when you turn on "panic_on_warn" the user expectation is and
> should be that the sites where WARN is used have been hand picked with
> consideration so that panic happens for a reason.
> 
> This has also been denoted repeatedly by Greg:
> 
> https://lore.kernel.org/linux-cve-announce/2024061828-CVE-2024-36975-6719@gregkh/
> 
> I should check this somewhere but actually these days a wrongly chosen
> WARN() might lead to CVE entry. That fix was by me but I never created
> the CVE.
> 
> Greg, did we have something under Documentation/ that would fully
> address the use of WARN?

Please see:
	https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
which describes that.  We should make it more explicit that any WARN()
or WARN_ON() calls that can be hit by user interactions somehow, will
end up getting a CVE id when we fix it up to not do so.

thanks,

greg k-h

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Mon Sep 23, 2024 at 5:48 PM EEST, Greg KH wrote:
> On Mon, Sep 23, 2024 at 05:31:47PM +0300, Jarkko Sakkinen wrote:
> > On Mon Sep 23, 2024 at 12:26 PM EEST, Herbert Xu wrote:
> >  > > +
> > > > > +		err = rng->read(rng, buffer, size, wait);
> > > > > +		if (WARN_ON_ONCE(err > 0 && err > size))
> > > > 
> > > > Are you sure you want to use WARN_ON_ONCE here instead of
> > > > pr_warn_once()? I.e. is it worth of taking down the whole
> > > > kernel?
> > >
> > > Absolutely.  If this triggers it's a serious kernel bug and we
> > > should gather as much information as possible.  pr_warn_once is
> > > not the same thing as WARN_ON_ONCE in terms of what it prints.
> > 
> > Personally I allow the use of WARN only as the last resort.
> > 
> > If you need stack printout you can always use dump_stack().
> > 
> > >
> > > If people want to turn WARNs into BUGs, then they've only got
> > > themselves to blame when the kernel goes down.  On the other
> > > hand perhaps they *do* want this to panic and we should hand
> > > it to them.
> > 
> > Actually when you turn on "panic_on_warn" the user expectation is and
> > should be that the sites where WARN is used have been hand picked with
> > consideration so that panic happens for a reason.
> > 
> > This has also been denoted repeatedly by Greg:
> > 
> > https://lore.kernel.org/linux-cve-announce/2024061828-CVE-2024-36975-6719@gregkh/
> > 
> > I should check this somewhere but actually these days a wrongly chosen
> > WARN() might lead to CVE entry. That fix was by me but I never created
> > the CVE.
> > 
> > Greg, did we have something under Documentation/ that would fully
> > address the use of WARN?
>
> Please see:
> 	https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
> which describes that.  We should make it more explicit that any WARN()
> or WARN_ON() calls that can be hit by user interactions somehow, will
> end up getting a CVE id when we fix it up to not do so.

I bookmarked this thanks :-)

Herbert, I'll do comprehensive testing tmrw by adding some invariants to
tpm2_get_random(). I'd really love to reimplement it because the current
implementation frankly sucks (and it's by me) but yep, we nee to fix it
first and foremost.

>
> thanks,
>
> greg k-h


BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Herbert Xu]

On Mon, Sep 23, 2024 at 04:48:27PM +0200, Greg KH wrote:
>
> Please see:
> 	https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
> which describes that.  We should make it more explicit that any WARN()
> or WARN_ON() calls that can be hit by user interactions somehow, will
> end up getting a CVE id when we fix it up to not do so.

If the aformentioned WARN_ON hits, then the driver has probabaly
already done a buffer overrun so it's a CVE anyway.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Tue Sep 24, 2024 at 1:32 AM EEST, Herbert Xu wrote:
> On Mon, Sep 23, 2024 at 04:48:27PM +0200, Greg KH wrote:
> >
> > Please see:
> > 	https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
> > which describes that.  We should make it more explicit that any WARN()
> > or WARN_ON() calls that can be hit by user interactions somehow, will
> > end up getting a CVE id when we fix it up to not do so.
>
> If the aformentioned WARN_ON hits, then the driver has probabaly
> already done a buffer overrun so it's a CVE anyway.

We'll see I finally got into testing this. Sorry for latencies, I'm
switching jobs and unfortunately German Post Office lost my priority
mail containing contracts (sent them from Finland to Berlin) so have
been signing, scanning etc. the whole day :-) My last week in the
current job, and next week is the first in the new job, so this
week is a bit bumpy.

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Tue Sep 24, 2024 at 7:05 PM EEST, Jarkko Sakkinen wrote:
> On Tue Sep 24, 2024 at 1:32 AM EEST, Herbert Xu wrote:
> > On Mon, Sep 23, 2024 at 04:48:27PM +0200, Greg KH wrote:
> > >
> > > Please see:
> > > 	https://www.kernel.org/doc/html/latest/process/deprecated.html#bug-and-bug-on
> > > which describes that.  We should make it more explicit that any WARN()
> > > or WARN_ON() calls that can be hit by user interactions somehow, will
> > > end up getting a CVE id when we fix it up to not do so.
> >
> > If the aformentioned WARN_ON hits, then the driver has probabaly
> > already done a buffer overrun so it's a CVE anyway.
>
> We'll see I finally got into testing this. Sorry for latencies, I'm
> switching jobs and unfortunately German Post Office lost my priority
> mail containing contracts (sent them from Finland to Berlin) so have
> been signing, scanning etc. the whole day :-) My last week in the
> current job, and next week is the first in the new job, so this
> week is a bit bumpy.

I get nothing with this:

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index aba024cbe7c5..856a8356d971 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -341,12 +341,15 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)

                dest_ptr += recd;
                total += recd;
+
+               WARN_ON(num_bytes < recd);
                num_bytes -= recd;
        } while (retries-- && total < max);

        tpm_buf_destroy(&buf);
        tpm2_end_auth_session(chip);

+       WARN_ON(total > max);
        return total ? total : -EIO;
 out:
        tpm_buf_destroy(&buf);

[WARN_ON()'s here are only for the temporary diff]

Call stack:

1. tpm2_get_random():
   https://elixir.bootlin.com/linux/v6.11-rc7/source/drivers/char/tpm/tpm2-cmd.c#L281
2. tpm_get_random():
   https://elixir.bootlin.com/linux/v6.11-rc7/source/drivers/char/tpm/tpm-interface.c#L430
3. tpm_hwrng_read():
   https://elixir.bootlin.com/linux/v6.11-rc7/source/drivers/char/tpm/tpm-chip.c#L524

Everything seems to have also appropriate range checks.

Without any traces that would provide more information I don't see
the smoking gun.

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Herbert Xu]

On Tue, Sep 24, 2024 at 08:43:00PM +0300, Jarkko Sakkinen wrote:
>
> Without any traces that would provide more information I don't see
> the smoking gun.

I haven't confirmed that it's definitely the tpm2 driver, it's just
based on the backtrace.  Hopefully my patch will confirm it one way
or the other.  Here is the backtrace:

[  100.784159] vmd 0000:c2:00.5: Bound to PCI domain 10002 
[  100.786209] Monitor-Mwait will be used to enter C-1 state 
[  100.786225] Monitor-Mwait will be used to enter C-2 state 
[  100.786244] ACPI: \_SB_.SCK0.C000: Found 2 idle states 
[  100.823093] input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0 
[  100.823636] ACPI: button: Power Button [PWRF] 
[  100.905756] ERST: Error Record Serialization Table (ERST) support is initialized. 
[  100.905858] pstore: Using crash dump compression: deflate 
[  100.905861] pstore: Registered erst as persistent store backend 
[  100.907044] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled 
[  100.908305] 00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A 
[  100.926608] 00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A 
[  100.942953] Non-volatile memory driver v1.3 
[  100.947908] tpm_tis MSFT0101:00: 2.0 TPM (device-id 0x1B, rev-id 22) 
[  101.226913] ACPI: bus type drm_connector registered 
[  101.229708] alg: ecdh-nist-p256 (ecdh-nist-p256-generic) is disabled due to FIPS 
[  101.229745] tpm tpm0: crypto ecdh allocation failed 
[  101.236311] tpm tpm0: A TPM error (708) occurred start auth session 
[  101.238797] ================================================================== 
[  101.238800] BUG: KASAN: slab-out-of-bounds in blake2s_update+0x135/0x2b0 
[  101.238808] Read of size 44 at addr ff11000167334d98 by task hwrng/318 
[  101.238811]  
[  101.238813] CPU: 26 UID: 0 PID: 318 Comm: hwrng Not tainted 6.11.0-0.rc5.22.el10.x86_64+debug #1 
[  101.238818] Hardware name: Supermicro SSG-110P-NTR10-EI018/X12SPO-NTF, BIOS 1.3 05/20/2022 
[  101.238820] Call Trace: 
[  101.238823]  <TASK> 
[  101.238826]  dump_stack_lvl+0x6f/0xb0 
[  101.238833]  ? blake2s_update+0x135/0x2b0 
[  101.238836]  print_address_description.constprop.0+0x88/0x330 
[  101.238843]  ? blake2s_update+0x135/0x2b0 
[  101.238847]  print_report+0x108/0x209 
[  101.238851]  ? blake2s_update+0x135/0x2b0 
[  101.238855]  ? __virt_addr_valid+0x20b/0x440 
[  101.238859]  ? blake2s_update+0x135/0x2b0 
[  101.238863]  kasan_report+0xa8/0xe0 
[  101.238868]  ? blake2s_update+0x135/0x2b0 
[  101.238874]  kasan_check_range+0x10f/0x1f0 
[  101.238879]  __asan_memcpy+0x23/0x60 
[  101.238883]  blake2s_update+0x135/0x2b0 
[  101.238887]  add_hwgenerator_randomness+0x3d/0xe0 
[  101.238895]  hwrng_fillfn+0x144/0x270 
[  101.238900]  ? __pfx_hwrng_fillfn+0x10/0x10 
[  101.238904]  kthread+0x2d2/0x3a0 
[  101.238908]  ? __pfx_kthread+0x10/0x10 
[  101.238912]  ret_from_fork+0x31/0x70 
[  101.238917]  ? __pfx_kthread+0x10/0x10 
[  101.238920]  ret_from_fork_asm+0x1a/0x30 
[  101.238929]  </TASK> 
[  101.238931]  
[  101.238932] Allocated by task 1: 
[  101.238934]  kasan_save_stack+0x30/0x50 
[  101.238937]  kasan_save_track+0x14/0x30 
[  101.238940]  __kasan_kmalloc+0x8f/0xa0 
[  101.238942]  __kmalloc_noprof+0x1fe/0x410 
[  101.238947]  kobj_map+0x7e/0x6d0 
[  101.238951]  cdev_add+0x92/0x180 
[  101.238954]  tty_cdev_add+0x17a/0x280 
[  101.238957]  tty_register_device_attr+0x401/0x740 
[  101.238960]  tty_register_driver+0x381/0x6f0 
[  101.238963]  vty_init+0x2c1/0x2f0 
[  101.238967]  tty_init+0x13b/0x150 
[  101.238970]  do_one_initcall+0x11c/0x5c0 
[  101.238975]  do_initcalls+0x1b4/0x1f0 
[  101.238980]  kernel_init_freeable+0x4ae/0x520 
[  101.238984]  kernel_init+0x1c/0x150 
[  101.238988]  ret_from_fork+0x31/0x70 
[  101.238991]  ret_from_fork_asm+0x1a/0x30 
[  101.238994]  
[  101.238995] The buggy address belongs to the object at ff11000167334d80 
[  101.238995]  which belongs to the cache kmalloc-64 of size 64 
[  101.238998] The buggy address is located 24 bytes inside of 
[  101.238998]  allocated 56-byte region [ff11000167334d80, ff11000167334db8) 
[  101.239002]  
[  101.239003] The buggy address belongs to the physical page: 
[  101.239004] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x167334 
[  101.239008] flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) 
[  101.239012] page_type: 0xfdffffff(slab) 
[  101.239016] raw: 0017ffffc0000000 ff1100010003c8c0 dead000000000122 0000000000000000 
[  101.239019] raw: 0000000000000000 0000000000200020 00000001fdffffff 0000000000000000 
[  101.239021] page dumped because: kasan: bad access detected 
[  101.239023]  
[  101.239024] Memory state around the buggy address: 
[  101.239025]  ff11000167334c80: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc 
[  101.239028]  ff11000167334d00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc 
[  101.239030] >ff11000167334d80: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc 
[  101.239031]                                         ^ 
[  101.239033]  ff11000167334e00: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc 
[  101.239035]  ff11000167334e80: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc 
[  101.239037] ================================================================== 
[  101.383067] rdac: device handler registered 
[  101.383412] hp_sw: device handler registered 
[  101.383415] emc: device handler registered 
[  101.383879] alua: device handler registered 
[  101.391255] xhci_hcd 0000:00:14.0: xHCI Host Controller 
[  101.391892] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 1 
[  101.393706] xhci_hcd 0000:00:14.0: hcc params 0x200077c1 hci version 0x100 quirks 0x0000000000009810 
[  101.399646] xhci_hcd 0000:00:14.0: xHCI Host Controller 
[  101.400136] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 2 
[  101.400163] xhci_hcd 0000:00:14.0: Host supports USB 3.0 SuperSpeed 
[  101.400818] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.11 
[  101.400823] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1 
[  101.400826] usb usb1: Product: xHCI Host Controller 
[  101.400829] usb usb1: Manufacturer: Linux 6.11.0-0.rc5.22.el10.x86_64+debug xhci-hcd 
[  101.400832] usb usb1: SerialNumber: 0000:00:14.0 
[  101.403055] hub 1-0:1.0: USB hub found 
[  101.403222] hub 1-0:1.0: 16 ports detected 
[  101.657974] usb usb2: New USB device found, idVendor=1d6b, idProduct=0003, bcdDevice= 6.11 
[  101.657982] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1 
[  101.657986] usb usb2: Product: xHCI Host Controller 
[  101.657990] usb usb2: Manufacturer: Linux 6.11.0-0.rc5.22.el10.x86_64+debug xhci-hcd 
[  101.657993] usb usb2: SerialNumber: 0000:00:14.0 
[  101.660659] hub 2-0:1.0: USB hub found 
[  101.660882] hub 2-0:1.0: 10 ports detected  {code}

Thanks,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Jarkko Sakkinen]

On Fri, 2024-09-27 at 08:42 +0800, Herbert Xu wrote:
> On Tue, Sep 24, 2024 at 08:43:00PM +0300, Jarkko Sakkinen wrote:
> > 
> > Without any traces that would provide more information I don't see
> > the smoking gun.
> 
> I haven't confirmed that it's definitely the tpm2 driver, it's just
> based on the backtrace.  Hopefully my patch will confirm it one way
> or the other.  Here is the backtrace:

Agreed.

> 
> [  100.784159] vmd 0000:c2:00.5: Bound to PCI domain 10002 
> [  100.786209] Monitor-Mwait will be used to enter C-1 state 
> [  100.786225] Monitor-Mwait will be used to enter C-2 state 
> [  100.786244] ACPI: \_SB_.SCK0.C000: Found 2 idle states 
> [  100.823093] input: Power Button as
> /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0 
> [  100.823636] ACPI: button: Power Button [PWRF] 
> [  100.905756] ERST: Error Record Serialization Table (ERST) support
> is initialized. 
> [  100.905858] pstore: Using crash dump compression: deflate 
> [  100.905861] pstore: Registered erst as persistent store backend 
> [  100.907044] Serial: 8250/16550 driver, 4 ports, IRQ sharing
> enabled 
> [  100.908305] 00:03: ttyS0 at I/O 0x3f8 (irq = 4, base_baud =
> 115200) is a 16550A 
> [  100.926608] 00:04: ttyS1 at I/O 0x2f8 (irq = 3, base_baud =
> 115200) is a 16550A 
> [  100.942953] Non-volatile memory driver v1.3 
> [  100.947908] tpm_tis MSFT0101:00: 2.0 TPM (device-id 0x1B, rev-id
> 22) 
> [  101.226913] ACPI: bus type drm_connector registered 
> [  101.229708] alg: ecdh-nist-p256 (ecdh-nist-p256-generic) is
> disabled due to FIPS 
> [  101.229745] tpm tpm0: crypto ecdh allocation failed 
> [  101.236311] tpm tpm0: A TPM error (708) occurred start auth

I guess it is TPM2_StartAuthSession returning TPM_RC_VALUE. Probably
James should look into this as the bus encryption code is clearly
tripping here.

I'm on second week on a new job so cannot promise any bandwidth
yet this week. Earliest next week...

BR, Jarkko

Re: [PATCH] hwrng: core - Add WARN_ON for buggy read return values

[Herbert Xu]

On Tue, Oct 08, 2024 at 02:28:27AM +0300, Jarkko Sakkinen wrote:
>
> I guess it is TPM2_StartAuthSession returning TPM_RC_VALUE. Probably
> James should look into this as the bus encryption code is clearly
> tripping here.

OK I've just got a confirmation from the lkp that the tpm RNG is
indeed buggy:

https://lore.kernel.org/oe-lkp/202503261331.d388f82a-lkp@intel.com/

Quoting from the kmsg:

kern  :err   : [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
kern  :info  : [   28.775547] resctrl: L3 allocation detected
kern  :warn  : [   28.777572] ------------[ cut here ]------------
kern  :info  : [   28.780433] resctrl: MB allocation detected
kern  :warn  : [   28.785745] WARNING: CPU: 46 PID: 576 at drivers/char/hw_random/core.c:188 hwrng_fillfn+0x19c/0x1f0

...

kern  :warn  : [   28.891243] RAX: 0000000000000903 RBX: ff110001077f6760 RCX: ffa000000ecb7e57

So the return value was 0x903, way bigger than what we asked for
(0x40).

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[PATCH] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

tpm2_start_auth_session() does not mask TPM RC correctly from the callers:

[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session

Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
error codes.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm2-sessions.c | 34 ++++++++++++++++----------------
 include/linux/tpm.h              |  1 +
 2 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 3f89635ba5e8..1ed23375e4cb 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -40,11 +40,6 @@
  *
  * These are the usage functions:
  *
- * tpm2_start_auth_session() which allocates the opaque auth structure
- *	and gets a session from the TPM.  This must be called before
- *	any of the following functions.  The session is protected by a
- *	session_key which is derived from a random salt value
- *	encrypted to the NULL seed.
  * tpm2_end_auth_session() kills the session and frees the resources.
  *	Under normal operation this function is done by
  *	tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 }
 
 /**
- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- * @chip: the TPM chip structure to create the session with
+ * tpm2_start_auth_session() - Create an a HMAC authentication session
+ * @chip:	A TPM chip
  *
- * This function loads the NULL seed from its saved context and starts
- * an authentication session on the null seed, fills in the
- * @chip->auth structure to contain all the session details necessary
- * for performing the HMAC, encrypt and decrypt operations and
- * returns.  The NULL seed is flushed before this function returns.
+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
+ * session. The null seed is flushed before the return.
  *
- * Return: zero on success or actual error encountered.
+ * Returns zero on success, or a POSIX error code.
  */
 int tpm2_start_auth_session(struct tpm_chip *chip)
 {
@@ -1024,11 +1016,19 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	/* hash algorithm for session */
 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
 
-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
 	tpm2_flush_context(chip, null_key);
-
-	if (rc == TPM2_RC_SUCCESS)
-		rc = tpm2_parse_start_auth_session(auth, &buf);
+	switch (rc) {
+	case TPM2_RC_SUCCESS:
+		break;
+	case TPM2_RC_SESSION_MEMORY:
+		rc = -ENOMEM;
+		goto out;
+	default:
+		rc = -EFAULT;
+		goto out;
+	}
+	rc = tpm2_parse_start_auth_session(auth, &buf);
 
 	tpm_buf_destroy(&buf);
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c1d3d60b416f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,6 +257,7 @@ enum tpm2_return_codes {
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 	TPM2_RC_RETRY		= 0x0922,
+	TPM2_RC_SESSION_MEMORY	= 0x0903,
 };
 
 enum tpm2_command_codes {
-- 
2.39.5

[PATCH v2] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

tpm2_start_auth_session() does not mask TPM RC correctly from the callers:

[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session

Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
error codes.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
- Investigate TPM rc only after destroying tpm_buf.
---
 drivers/char/tpm/tpm2-sessions.c | 29 +++++++++++++++--------------
 include/linux/tpm.h              |  1 +
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 3f89635ba5e8..da382b86dc41 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -40,11 +40,6 @@
  *
  * These are the usage functions:
  *
- * tpm2_start_auth_session() which allocates the opaque auth structure
- *	and gets a session from the TPM.  This must be called before
- *	any of the following functions.  The session is protected by a
- *	session_key which is derived from a random salt value
- *	encrypted to the NULL seed.
  * tpm2_end_auth_session() kills the session and frees the resources.
  *	Under normal operation this function is done by
  *	tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 }
 
 /**
- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- * @chip: the TPM chip structure to create the session with
+ * tpm2_start_auth_session() - Create an a HMAC authentication session
+ * @chip:	A TPM chip
  *
- * This function loads the NULL seed from its saved context and starts
- * an authentication session on the null seed, fills in the
- * @chip->auth structure to contain all the session details necessary
- * for performing the HMAC, encrypt and decrypt operations and
- * returns.  The NULL seed is flushed before this function returns.
+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
+ * session. The null seed is flushed before the return.
  *
- * Return: zero on success or actual error encountered.
+ * Returns zero on success, or a POSIX error code.
  */
 int tpm2_start_auth_session(struct tpm_chip *chip)
 {
@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	/* hash algorithm for session */
 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
 
-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
 	tpm2_flush_context(chip, null_key);
 
 	if (rc == TPM2_RC_SUCCESS)
@@ -1032,6 +1024,15 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 
 	tpm_buf_destroy(&buf);
 
+	switch (rc) {
+	case TPM2_RC_SESSION_MEMORY:
+		rc = -ENOMEM;
+		goto out;
+	default:
+		rc = -EFAULT;
+		goto out;
+	}
+
 	if (rc == TPM2_RC_SUCCESS) {
 		chip->auth = auth;
 		return 0;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c1d3d60b416f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,6 +257,7 @@ enum tpm2_return_codes {
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 	TPM2_RC_RETRY		= 0x0922,
+	TPM2_RC_SESSION_MEMORY	= 0x0903,
 };
 
 enum tpm2_command_codes {
-- 
2.39.5

[PATCH v3] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

tpm2_start_auth_session() does not mask TPM RC correctly from the callers:

[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session

Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
error codes.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v3:
- rc > 0
v2:
- Investigate TPM rc only after destroying tpm_buf.
---
 drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++++++++--------------
 include/linux/tpm.h              |  1 +
 2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 3f89635ba5e8..abd54fb0a45a 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -40,11 +40,6 @@
  *
  * These are the usage functions:
  *
- * tpm2_start_auth_session() which allocates the opaque auth structure
- *	and gets a session from the TPM.  This must be called before
- *	any of the following functions.  The session is protected by a
- *	session_key which is derived from a random salt value
- *	encrypted to the NULL seed.
  * tpm2_end_auth_session() kills the session and frees the resources.
  *	Under normal operation this function is done by
  *	tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 }
 
 /**
- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- * @chip: the TPM chip structure to create the session with
+ * tpm2_start_auth_session() - Create an a HMAC authentication session
+ * @chip:	A TPM chip
  *
- * This function loads the NULL seed from its saved context and starts
- * an authentication session on the null seed, fills in the
- * @chip->auth structure to contain all the session details necessary
- * for performing the HMAC, encrypt and decrypt operations and
- * returns.  The NULL seed is flushed before this function returns.
+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
+ * session. The null seed is flushed before the return.
  *
- * Return: zero on success or actual error encountered.
+ * Returns zero on success, or a POSIX error code.
  */
 int tpm2_start_auth_session(struct tpm_chip *chip)
 {
@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	/* hash algorithm for session */
 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
 
-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
 	tpm2_flush_context(chip, null_key);
 
 	if (rc == TPM2_RC_SUCCESS)
@@ -1032,6 +1024,17 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 
 	tpm_buf_destroy(&buf);
 
+	if (rc > 0) {
+		switch (rc) {
+		case TPM2_RC_SESSION_MEMORY:
+			rc = -ENOMEM;
+			goto out;
+		default:
+			rc = -EFAULT;
+			goto out;
+		}
+	}
+
 	if (rc == TPM2_RC_SUCCESS) {
 		chip->auth = auth;
 		return 0;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c1d3d60b416f 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,6 +257,7 @@ enum tpm2_return_codes {
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 	TPM2_RC_RETRY		= 0x0922,
+	TPM2_RC_SESSION_MEMORY	= 0x0903,
 };
 
 enum tpm2_command_codes {
-- 
2.39.5

Re: [PATCH v3] tpm: Mask TPM RC in tpm2_start_auth_session()

[Stefano Garzarella]

On Mon, Apr 07, 2025 at 10:20:57AM +0300, Jarkko Sakkinen wrote:
>tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
>
>[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
>
>Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
>error codes.
>
>Cc: stable@vger.kernel.org # v6.10+
>Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
>Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
>Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
>Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>---
>v3:
>- rc > 0
>v2:
>- Investigate TPM rc only after destroying tpm_buf.
>---
> drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++++++++--------------
> include/linux/tpm.h              |  1 +
> 2 files changed, 18 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>index 3f89635ba5e8..abd54fb0a45a 100644
>--- a/drivers/char/tpm/tpm2-sessions.c
>+++ b/drivers/char/tpm/tpm2-sessions.c
>@@ -40,11 +40,6 @@
>  *
>  * These are the usage functions:
>  *
>- * tpm2_start_auth_session() which allocates the opaque auth structure
>- *	and gets a session from the TPM.  This must be called before
>- *	any of the following functions.  The session is protected by a
>- *	session_key which is derived from a random salt value
>- *	encrypted to the NULL seed.
>  * tpm2_end_auth_session() kills the session and frees the resources.
>  *	Under normal operation this function is done by
>  *	tpm_buf_check_hmac_response(), so this is only to be used on
>@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> }
>
> /**
>- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
>- * @chip: the TPM chip structure to create the session with
>+ * tpm2_start_auth_session() - Create an a HMAC authentication session
>+ * @chip:	A TPM chip
>  *
>- * This function loads the NULL seed from its saved context and starts
>- * an authentication session on the null seed, fills in the
>- * @chip->auth structure to contain all the session details necessary
>- * for performing the HMAC, encrypt and decrypt operations and
>- * returns.  The NULL seed is flushed before this function returns.
>+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
>+ * session. The null seed is flushed before the return.
>  *
>- * Return: zero on success or actual error encountered.
>+ * Returns zero on success, or a POSIX error code.
>  */
> int tpm2_start_auth_session(struct tpm_chip *chip)
> {
>@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> 	/* hash algorithm for session */
> 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>
>-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
>+	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
> 	tpm2_flush_context(chip, null_key);
>
> 	if (rc == TPM2_RC_SUCCESS)
>@@ -1032,6 +1024,17 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>
> 	tpm_buf_destroy(&buf);
>
>+	if (rc > 0) {

To avoid the nesting blocks, can we include `TPM2_RC_SUCCESS` case in 
the switch or move the `if (rc == TPM2_RC_SUCCESS)` before it?

Thanks,
Stefano

>+		switch (rc) {
>+		case TPM2_RC_SESSION_MEMORY:
>+			rc = -ENOMEM;
>+			goto out;
>+		default:
>+			rc = -EFAULT;
>+			goto out;
>+		}
>+	}
>+
> 	if (rc == TPM2_RC_SUCCESS) {
> 		chip->auth = auth;
> 		return 0;
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index 6c3125300c00..c1d3d60b416f 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -257,6 +257,7 @@ enum tpm2_return_codes {
> 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
> 	TPM2_RC_REFERENCE_H0	= 0x0910,
> 	TPM2_RC_RETRY		= 0x0922,
>+	TPM2_RC_SESSION_MEMORY	= 0x0903,
> };
>
> enum tpm2_command_codes {
>-- 
>2.39.5
>
>

Re: [PATCH v3] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Mon, Apr 07, 2025 at 10:04:09AM +0200, Stefano Garzarella wrote:
> On Mon, Apr 07, 2025 at 10:20:57AM +0300, Jarkko Sakkinen wrote:
> > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> > 
> > [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> > 
> > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> > error codes.
> > 
> > Cc: stable@vger.kernel.org # v6.10+
> > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v3:
> > - rc > 0
> > v2:
> > - Investigate TPM rc only after destroying tpm_buf.
> > ---
> > drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++++++++--------------
> > include/linux/tpm.h              |  1 +
> > 2 files changed, 18 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index 3f89635ba5e8..abd54fb0a45a 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -40,11 +40,6 @@
> >  *
> >  * These are the usage functions:
> >  *
> > - * tpm2_start_auth_session() which allocates the opaque auth structure
> > - *	and gets a session from the TPM.  This must be called before
> > - *	any of the following functions.  The session is protected by a
> > - *	session_key which is derived from a random salt value
> > - *	encrypted to the NULL seed.
> >  * tpm2_end_auth_session() kills the session and frees the resources.
> >  *	Under normal operation this function is done by
> >  *	tpm_buf_check_hmac_response(), so this is only to be used on
> > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> > }
> > 
> > /**
> > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> > - * @chip: the TPM chip structure to create the session with
> > + * tpm2_start_auth_session() - Create an a HMAC authentication session
> > + * @chip:	A TPM chip
> >  *
> > - * This function loads the NULL seed from its saved context and starts
> > - * an authentication session on the null seed, fills in the
> > - * @chip->auth structure to contain all the session details necessary
> > - * for performing the HMAC, encrypt and decrypt operations and
> > - * returns.  The NULL seed is flushed before this function returns.
> > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> > + * session. The null seed is flushed before the return.
> >  *
> > - * Return: zero on success or actual error encountered.
> > + * Returns zero on success, or a POSIX error code.
> >  */
> > int tpm2_start_auth_session(struct tpm_chip *chip)
> > {
> > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > 	/* hash algorithm for session */
> > 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> > 
> > -	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > +	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
> > 	tpm2_flush_context(chip, null_key);
> > 
> > 	if (rc == TPM2_RC_SUCCESS)
> > @@ -1032,6 +1024,17 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > 
> > 	tpm_buf_destroy(&buf);
> > 
> > +	if (rc > 0) {
> 
> To avoid the nesting blocks, can we include `TPM2_RC_SUCCESS` case in the
> switch or move the `if (rc == TPM2_RC_SUCCESS)` before it?

What do you mean by "avoiding nesting blocks"?

> 
> Thanks,
> Stefano

BR, Jarkko

Re: [PATCH v3] tpm: Mask TPM RC in tpm2_start_auth_session()

[Stefano Garzarella]

On Mon, Apr 07, 2025 at 02:30:05PM +0300, Jarkko Sakkinen wrote:
>On Mon, Apr 07, 2025 at 10:04:09AM +0200, Stefano Garzarella wrote:
>> On Mon, Apr 07, 2025 at 10:20:57AM +0300, Jarkko Sakkinen wrote:
>> > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
>> >
>> > [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
>> >
>> > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
>> > error codes.
>> >
>> > Cc: stable@vger.kernel.org # v6.10+
>> > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
>> > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
>> > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
>> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>> > ---
>> > v3:
>> > - rc > 0
>> > v2:
>> > - Investigate TPM rc only after destroying tpm_buf.
>> > ---
>> > drivers/char/tpm/tpm2-sessions.c | 31 +++++++++++++++++--------------
>> > include/linux/tpm.h              |  1 +
>> > 2 files changed, 18 insertions(+), 14 deletions(-)
>> >
>> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>> > index 3f89635ba5e8..abd54fb0a45a 100644
>> > --- a/drivers/char/tpm/tpm2-sessions.c
>> > +++ b/drivers/char/tpm/tpm2-sessions.c
>> > @@ -40,11 +40,6 @@
>> >  *
>> >  * These are the usage functions:
>> >  *
>> > - * tpm2_start_auth_session() which allocates the opaque auth structure
>> > - *	and gets a session from the TPM.  This must be called before
>> > - *	any of the following functions.  The session is protected by a
>> > - *	session_key which is derived from a random salt value
>> > - *	encrypted to the NULL seed.
>> >  * tpm2_end_auth_session() kills the session and frees the resources.
>> >  *	Under normal operation this function is done by
>> >  *	tpm_buf_check_hmac_response(), so this is only to be used on
>> > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>> > }
>> >
>> > /**
>> > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
>> > - * @chip: the TPM chip structure to create the session with
>> > + * tpm2_start_auth_session() - Create an a HMAC authentication session
>> > + * @chip:	A TPM chip
>> >  *
>> > - * This function loads the NULL seed from its saved context and starts
>> > - * an authentication session on the null seed, fills in the
>> > - * @chip->auth structure to contain all the session details necessary
>> > - * for performing the HMAC, encrypt and decrypt operations and
>> > - * returns.  The NULL seed is flushed before this function returns.
>> > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
>> > + * session. The null seed is flushed before the return.
>> >  *
>> > - * Return: zero on success or actual error encountered.
>> > + * Returns zero on success, or a POSIX error code.
>> >  */
>> > int tpm2_start_auth_session(struct tpm_chip *chip)
>> > {
>> > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>> > 	/* hash algorithm for session */
>> > 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>> >
>> > -	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
>> > +	rc = tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession");
>> > 	tpm2_flush_context(chip, null_key);
>> >
>> > 	if (rc == TPM2_RC_SUCCESS)
>> > @@ -1032,6 +1024,17 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>> >
>> > 	tpm_buf_destroy(&buf);
>> >
>> > +	if (rc > 0) {
>>
>> To avoid the nesting blocks, can we include `TPM2_RC_SUCCESS` case in the
>> switch or move the `if (rc == TPM2_RC_SUCCESS)` before it?
>
>What do you mean by "avoiding nesting blocks"?

Ooops, I thought `rc` was unsigned always returning TPM2_RC_* values,
but it looks it's not the case.

I meant the switch "block" inside the if block, at the end exactly what
you did in tpm_to_ret() in v4 :-)

Thanks,
Stefano

[PATCH v4] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

tpm2_start_auth_session() does not mask TPM RC correctly from the callers:

[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session

Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
error codes.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v4:
- tpm_to_ret()
v3:
- rc > 0
v2:
- Investigate TPM rc only after destroying tpm_buf.
---
 drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
 include/linux/tpm.h              | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 3f89635ba5e8..102e099f22c1 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -40,11 +40,6 @@
  *
  * These are the usage functions:
  *
- * tpm2_start_auth_session() which allocates the opaque auth structure
- *	and gets a session from the TPM.  This must be called before
- *	any of the following functions.  The session is protected by a
- *	session_key which is derived from a random salt value
- *	encrypted to the NULL seed.
  * tpm2_end_auth_session() kills the session and frees the resources.
  *	Under normal operation this function is done by
  *	tpm_buf_check_hmac_response(), so this is only to be used on
@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 }
 
 /**
- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
- * @chip: the TPM chip structure to create the session with
+ * tpm2_start_auth_session() - Create an a HMAC authentication session
+ * @chip:	A TPM chip
  *
- * This function loads the NULL seed from its saved context and starts
- * an authentication session on the null seed, fills in the
- * @chip->auth structure to contain all the session details necessary
- * for performing the HMAC, encrypt and decrypt operations and
- * returns.  The NULL seed is flushed before this function returns.
+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
+ * session. The null seed is flushed before the return.
  *
- * Return: zero on success or actual error encountered.
+ * Returns zero on success, or a POSIX error code.
  */
 int tpm2_start_auth_session(struct tpm_chip *chip)
 {
@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	/* hash algorithm for session */
 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
 
-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
+	rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
 	tpm2_flush_context(chip, null_key);
 
 	if (rc == TPM2_RC_SUCCESS)
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..c826d5a9d894 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -257,8 +257,29 @@ enum tpm2_return_codes {
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 	TPM2_RC_RETRY		= 0x0922,
+	TPM2_RC_SESSION_MEMORY	= 0x0903,
 };
 
+/*
+ * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
+ * fallback return value is -EFAULT.
+ */
+static inline ssize_t tpm_to_ret(ssize_t ret)
+{
+	/* Already a POSIX error: */
+	if (ret < 0)
+		return ret;
+
+	switch (ret) {
+	case TPM2_RC_SUCCESS:
+		return 0;
+	case TPM2_RC_SESSION_MEMORY:
+		return -ENOMEM;
+	default:
+		return -EFAULT;
+	}
+}
+
 enum tpm2_command_codes {
 	TPM2_CC_FIRST		        = 0x011F,
 	TPM2_CC_HIERARCHY_CONTROL       = 0x0121,
-- 
2.39.5

Re: [PATCH v4] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> 
> [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> 
> Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> error codes.
> 
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v4:
> - tpm_to_ret()
> v3:
> - rc > 0
> v2:
> - Investigate TPM rc only after destroying tpm_buf.
> ---
>  drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
>  include/linux/tpm.h              | 21 +++++++++++++++++++++
>  2 files changed, 27 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 3f89635ba5e8..102e099f22c1 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -40,11 +40,6 @@
>   *
>   * These are the usage functions:
>   *
> - * tpm2_start_auth_session() which allocates the opaque auth structure
> - *	and gets a session from the TPM.  This must be called before
> - *	any of the following functions.  The session is protected by a
> - *	session_key which is derived from a random salt value
> - *	encrypted to the NULL seed.
>   * tpm2_end_auth_session() kills the session and frees the resources.
>   *	Under normal operation this function is done by
>   *	tpm_buf_check_hmac_response(), so this is only to be used on
> @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>  }
>  
>  /**
> - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> - * @chip: the TPM chip structure to create the session with
> + * tpm2_start_auth_session() - Create an a HMAC authentication session
> + * @chip:	A TPM chip
>   *
> - * This function loads the NULL seed from its saved context and starts
> - * an authentication session on the null seed, fills in the
> - * @chip->auth structure to contain all the session details necessary
> - * for performing the HMAC, encrypt and decrypt operations and
> - * returns.  The NULL seed is flushed before this function returns.
> + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> + * session. The null seed is flushed before the return.
>   *
> - * Return: zero on success or actual error encountered.
> + * Returns zero on success, or a POSIX error code.
>   */
>  int tpm2_start_auth_session(struct tpm_chip *chip)
>  {
> @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>  	/* hash algorithm for session */
>  	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> +	rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));

The cool thing here is that e.g., in the case of
tpm2_start_auth_session, there is two implementation options:

1. tpm_to_ret(tpm2_start_auth_session)
2. tpm_to_ret(tpm_transmit_cmd)

Just want to expose this choice..


>  	tpm2_flush_context(chip, null_key);
>  
>  	if (rc == TPM2_RC_SUCCESS)
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 6c3125300c00..c826d5a9d894 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -257,8 +257,29 @@ enum tpm2_return_codes {
>  	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
>  	TPM2_RC_REFERENCE_H0	= 0x0910,
>  	TPM2_RC_RETRY		= 0x0922,
> +	TPM2_RC_SESSION_MEMORY	= 0x0903,
>  };
>  
> +/*
> + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> + * fallback return value is -EFAULT.
> + */
> +static inline ssize_t tpm_to_ret(ssize_t ret)
> +{
> +	/* Already a POSIX error: */
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (ret) {
> +	case TPM2_RC_SUCCESS:
> +		return 0;
> +	case TPM2_RC_SESSION_MEMORY:
> +		return -ENOMEM;
> +	default:
> +		return -EFAULT;
> +	}
> +}
> +
>  enum tpm2_command_codes {
>  	TPM2_CC_FIRST		        = 0x011F,
>  	TPM2_CC_HIERARCHY_CONTROL       = 0x0121,
> -- 
> 2.39.5
> 

BR, Jarkko

Re: [PATCH v4] tpm: Mask TPM RC in tpm2_start_auth_session()

[Stefano Garzarella]

On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
>tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
>
>[   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
>
>Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
>error codes.
>
>Cc: stable@vger.kernel.org # v6.10+
>Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
>Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
>Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
>Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>---
>v4:
>- tpm_to_ret()
>v3:
>- rc > 0
>v2:
>- Investigate TPM rc only after destroying tpm_buf.
>---
> drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> include/linux/tpm.h              | 21 +++++++++++++++++++++
> 2 files changed, 27 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>index 3f89635ba5e8..102e099f22c1 100644
>--- a/drivers/char/tpm/tpm2-sessions.c
>+++ b/drivers/char/tpm/tpm2-sessions.c
>@@ -40,11 +40,6 @@
>  *
>  * These are the usage functions:
>  *
>- * tpm2_start_auth_session() which allocates the opaque auth structure
>- *	and gets a session from the TPM.  This must be called before
>- *	any of the following functions.  The session is protected by a
>- *	session_key which is derived from a random salt value
>- *	encrypted to the NULL seed.
>  * tpm2_end_auth_session() kills the session and frees the resources.
>  *	Under normal operation this function is done by
>  *	tpm_buf_check_hmac_response(), so this is only to be used on
>@@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> }
>
> /**
>- * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
>- * @chip: the TPM chip structure to create the session with
>+ * tpm2_start_auth_session() - Create an a HMAC authentication session
>+ * @chip:	A TPM chip
>  *
>- * This function loads the NULL seed from its saved context and starts
>- * an authentication session on the null seed, fills in the
>- * @chip->auth structure to contain all the session details necessary
>- * for performing the HMAC, encrypt and decrypt operations and
>- * returns.  The NULL seed is flushed before this function returns.
>+ * Loads the ephemeral key (null seed), and starts an HMAC authenticated
>+ * session. The null seed is flushed before the return.
>  *
>- * Return: zero on success or actual error encountered.
>+ * Returns zero on success, or a POSIX error code.
>  */
> int tpm2_start_auth_session(struct tpm_chip *chip)
> {
>@@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> 	/* hash algorithm for session */
> 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>
>-	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
>+	rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> 	tpm2_flush_context(chip, null_key);
>
> 	if (rc == TPM2_RC_SUCCESS)
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index 6c3125300c00..c826d5a9d894 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -257,8 +257,29 @@ enum tpm2_return_codes {
> 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
> 	TPM2_RC_REFERENCE_H0	= 0x0910,
> 	TPM2_RC_RETRY		= 0x0922,
>+	TPM2_RC_SESSION_MEMORY	= 0x0903,

nit: the other values are in ascending order, should we keep it or is it 
not important?

(more a question for me than for the patch)

> };
>
>+/*
>+ * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
>+ * fallback return value is -EFAULT.
>+ */
>+static inline ssize_t tpm_to_ret(ssize_t ret)
>+{
>+	/* Already a POSIX error: */
>+	if (ret < 0)
>+		return ret;
>+
>+	switch (ret) {
>+	case TPM2_RC_SUCCESS:
>+		return 0;
>+	case TPM2_RC_SESSION_MEMORY:
>+		return -ENOMEM;
>+	default:
>+		return -EFAULT;
>+	}
>+}

I like this and in the future we could reuse it in different places like 
tpm2_load_context() and tpm2_save_context().

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>


BTW for my understading, looking at that code (sorry if the answer is 
obvious, but I'm learning) I'm confused about the use of 
tpm2_rc_value().

For example in tpm2_load_context() we have:

     	rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
     	...
	} else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
		   rc == TPM2_RC_REFERENCE_H0) {

While in tpm2_save_context(), we have:

	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
	...
	} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {

So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only 
sometimes, what's the reason?

Thanks,
Stefano

Re: [PATCH v4] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Mon, Apr 07, 2025 at 03:51:21PM +0200, Stefano Garzarella wrote:
> On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> > 
> > [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> > 
> > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> > error codes.
> > 
> > Cc: stable@vger.kernel.org # v6.10+
> > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v4:
> > - tpm_to_ret()
> > v3:
> > - rc > 0
> > v2:
> > - Investigate TPM rc only after destroying tpm_buf.
> > ---
> > drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> > include/linux/tpm.h              | 21 +++++++++++++++++++++
> > 2 files changed, 27 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index 3f89635ba5e8..102e099f22c1 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -40,11 +40,6 @@
> >  *
> >  * These are the usage functions:
> >  *
> > - * tpm2_start_auth_session() which allocates the opaque auth structure
> > - *	and gets a session from the TPM.  This must be called before
> > - *	any of the following functions.  The session is protected by a
> > - *	session_key which is derived from a random salt value
> > - *	encrypted to the NULL seed.
> >  * tpm2_end_auth_session() kills the session and frees the resources.
> >  *	Under normal operation this function is done by
> >  *	tpm_buf_check_hmac_response(), so this is only to be used on
> > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> > }
> > 
> > /**
> > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> > - * @chip: the TPM chip structure to create the session with
> > + * tpm2_start_auth_session() - Create an a HMAC authentication session
> > + * @chip:	A TPM chip
> >  *
> > - * This function loads the NULL seed from its saved context and starts
> > - * an authentication session on the null seed, fills in the
> > - * @chip->auth structure to contain all the session details necessary
> > - * for performing the HMAC, encrypt and decrypt operations and
> > - * returns.  The NULL seed is flushed before this function returns.
> > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> > + * session. The null seed is flushed before the return.
> >  *
> > - * Return: zero on success or actual error encountered.
> > + * Returns zero on success, or a POSIX error code.
> >  */
> > int tpm2_start_auth_session(struct tpm_chip *chip)
> > {
> > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > 	/* hash algorithm for session */
> > 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> > 
> > -	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > +	rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> > 	tpm2_flush_context(chip, null_key);
> > 
> > 	if (rc == TPM2_RC_SUCCESS)
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index 6c3125300c00..c826d5a9d894 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -257,8 +257,29 @@ enum tpm2_return_codes {
> > 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
> > 	TPM2_RC_REFERENCE_H0	= 0x0910,
> > 	TPM2_RC_RETRY		= 0x0922,
> > +	TPM2_RC_SESSION_MEMORY	= 0x0903,
> 
> nit: the other values are in ascending order, should we keep it or is it not
> important?
> 
> (more a question for me than for the patch)

nope

> 
> > };
> > 
> > +/*
> > + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> > + * fallback return value is -EFAULT.
> > + */
> > +static inline ssize_t tpm_to_ret(ssize_t ret)
> > +{
> > +	/* Already a POSIX error: */
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	switch (ret) {
> > +	case TPM2_RC_SUCCESS:
> > +		return 0;
> > +	case TPM2_RC_SESSION_MEMORY:
> > +		return -ENOMEM;
> > +	default:
> > +		return -EFAULT;
> > +	}
> > +}
> 
> I like this and in the future we could reuse it in different places like
> tpm2_load_context() and tpm2_save_context().
> 
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> 
> 
> BTW for my understading, looking at that code (sorry if the answer is
> obvious, but I'm learning) I'm confused about the use of tpm2_rc_value().
> 
> For example in tpm2_load_context() we have:
> 
>     	rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
>     	...
> 	} else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
> 		   rc == TPM2_RC_REFERENCE_H0) {
> 
> While in tpm2_save_context(), we have:
> 
> 	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> 	...
> 	} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
> 
> So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only
> sometimes, what's the reason?

Good catch, I'll update...

TPM RC is a struct or bitfield.

> 
> Thanks,
> Stefano
> 
> 

BR, Jarkko

Re: [PATCH v4] tpm: Mask TPM RC in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Mon, Apr 07, 2025 at 09:13:37PM +0300, Jarkko Sakkinen wrote:
> On Mon, Apr 07, 2025 at 03:51:21PM +0200, Stefano Garzarella wrote:
> > On Mon, Apr 07, 2025 at 03:28:05PM +0300, Jarkko Sakkinen wrote:
> > > tpm2_start_auth_session() does not mask TPM RC correctly from the callers:
> > > 
> > > [   28.766528] tpm tpm0: A TPM error (2307) occurred start auth session
> > > 
> > > Process TPM RCs inside tpm2_start_auth_session(), and map them to POSIX
> > > error codes.
> > > 
> > > Cc: stable@vger.kernel.org # v6.10+
> > > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > > Reported-by: Herbert Xu <herbert@gondor.apana.org.au>
> > > Closes: https://lore.kernel.org/linux-integrity/Z_NgdRHuTKP6JK--@gondor.apana.org.au/
> > > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > > ---
> > > v4:
> > > - tpm_to_ret()
> > > v3:
> > > - rc > 0
> > > v2:
> > > - Investigate TPM rc only after destroying tpm_buf.
> > > ---
> > > drivers/char/tpm/tpm2-sessions.c | 20 ++++++--------------
> > > include/linux/tpm.h              | 21 +++++++++++++++++++++
> > > 2 files changed, 27 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > > index 3f89635ba5e8..102e099f22c1 100644
> > > --- a/drivers/char/tpm/tpm2-sessions.c
> > > +++ b/drivers/char/tpm/tpm2-sessions.c
> > > @@ -40,11 +40,6 @@
> > >  *
> > >  * These are the usage functions:
> > >  *
> > > - * tpm2_start_auth_session() which allocates the opaque auth structure
> > > - *	and gets a session from the TPM.  This must be called before
> > > - *	any of the following functions.  The session is protected by a
> > > - *	session_key which is derived from a random salt value
> > > - *	encrypted to the NULL seed.
> > >  * tpm2_end_auth_session() kills the session and frees the resources.
> > >  *	Under normal operation this function is done by
> > >  *	tpm_buf_check_hmac_response(), so this is only to be used on
> > > @@ -963,16 +958,13 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> > > }
> > > 
> > > /**
> > > - * tpm2_start_auth_session() - create a HMAC authentication session with the TPM
> > > - * @chip: the TPM chip structure to create the session with
> > > + * tpm2_start_auth_session() - Create an a HMAC authentication session
> > > + * @chip:	A TPM chip
> > >  *
> > > - * This function loads the NULL seed from its saved context and starts
> > > - * an authentication session on the null seed, fills in the
> > > - * @chip->auth structure to contain all the session details necessary
> > > - * for performing the HMAC, encrypt and decrypt operations and
> > > - * returns.  The NULL seed is flushed before this function returns.
> > > + * Loads the ephemeral key (null seed), and starts an HMAC authenticated
> > > + * session. The null seed is flushed before the return.
> > >  *
> > > - * Return: zero on success or actual error encountered.
> > > + * Returns zero on success, or a POSIX error code.
> > >  */
> > > int tpm2_start_auth_session(struct tpm_chip *chip)
> > > {
> > > @@ -1024,7 +1016,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> > > 	/* hash algorithm for session */
> > > 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> > > 
> > > -	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > > +	rc = tpm_to_ret(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> > > 	tpm2_flush_context(chip, null_key);
> > > 
> > > 	if (rc == TPM2_RC_SUCCESS)
> > > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > > index 6c3125300c00..c826d5a9d894 100644
> > > --- a/include/linux/tpm.h
> > > +++ b/include/linux/tpm.h
> > > @@ -257,8 +257,29 @@ enum tpm2_return_codes {
> > > 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
> > > 	TPM2_RC_REFERENCE_H0	= 0x0910,
> > > 	TPM2_RC_RETRY		= 0x0922,
> > > +	TPM2_RC_SESSION_MEMORY	= 0x0903,
> > 
> > nit: the other values are in ascending order, should we keep it or is it not
> > important?
> > 
> > (more a question for me than for the patch)
> 
> nope
> 
> > 
> > > };
> > > 
> > > +/*
> > > + * Convert a return value from tpm_transmit_cmd() to a POSIX return value. The
> > > + * fallback return value is -EFAULT.
> > > + */
> > > +static inline ssize_t tpm_to_ret(ssize_t ret)
> > > +{
> > > +	/* Already a POSIX error: */
> > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > > +	switch (ret) {
> > > +	case TPM2_RC_SUCCESS:
> > > +		return 0;
> > > +	case TPM2_RC_SESSION_MEMORY:
> > > +		return -ENOMEM;
> > > +	default:
> > > +		return -EFAULT;
> > > +	}
> > > +}
> > 
> > I like this and in the future we could reuse it in different places like
> > tpm2_load_context() and tpm2_save_context().
> > 
> > Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> > 
> > 
> > BTW for my understading, looking at that code (sorry if the answer is
> > obvious, but I'm learning) I'm confused about the use of tpm2_rc_value().
> > 
> > For example in tpm2_load_context() we have:
> > 
> >     	rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
> >     	...
> > 	} else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
> > 		   rc == TPM2_RC_REFERENCE_H0) {
> > 
> > While in tpm2_save_context(), we have:
> > 
> > 	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> > 	...
> > 	} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
> > 
> > So to check TPM2_RC_REFERENCE_H0 we are using tpm2_rc_value() only
> > sometimes, what's the reason?
> 
> Good catch, I'll update...
> 
> TPM RC is a struct or bitfield.

Applied to my -next: https://web.git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/log/?h=next

BR, Jarkko