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Message-ID: <g3ayj2gxzbjmkghbwskrbza2fn546obkul3zistnxvoeie7ync@fpejz33wnpmq>
Date: Tue, 30 Sep 2025 15:20:07 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-integrity@...r.kernel.org, dpsmith@...rtussolutions.com,
ross.philipson@...cle.com, Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>,
Stefan Berger <stefanb@...ux.ibm.com>, Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
David Howells <dhowells@...hat.com>, Paul Moore <paul@...l-moore.com>,
James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>,
James Bottomley <James.Bottomley@...senpartnership.com>, Mimi Zohar <zohar@...ux.ibm.com>,
open list <linux-kernel@...r.kernel.org>, "open list:KEYS/KEYRINGS" <keyrings@...r.kernel.org>,
"open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v3 10/10] tpm-buf: Enable managed and stack allocations.
On Tue, Sep 30, 2025 at 04:11:00PM +0300, Jarkko Sakkinen wrote:
>On Tue, Sep 30, 2025 at 02:44:52PM +0200, Stefano Garzarella wrote:
>> On Mon, Sep 29, 2025 at 10:48:32PM +0300, Jarkko Sakkinen wrote:
>> > From: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
>> >
>> > Decouple kzalloc from buffer creation, so that a managed allocation can be
>> > done trivially:
>> >
>> > struct tpm_buf *buf __free(kfree) buf = kzalloc(TPM_BUFSIZE,
>> ^
>> In the code, we use PAGE_SIZE instead of TPM_BUFSIZE with kzalloc().
>> Should we do the same in this example? (Perhaps adding the reason, if you
>> think it would be useful)
>
>I think that should be fixed up in the patch and use TPM_BUFSIZE
>consistently for kzallocs. Thanks for the remark.
I thought it was done on purpose to alleviate pressure on the allocator
regardless of the page size value.
In any case, it's up to you, I would just be consistent between the
example in the commit and the code.
>
>>
>> > GFP_KERNEL);
>> > if (!buf)
>> > return -ENOMEM;
>> > tpm_buf_init(buf, TPM_BUFSIZE);
>> >
>> > Alternatively, stack allocations are also possible:
>> >
>> > u8 buf_data[512];
>> > struct tpm_buf *buf = (struct tpm_buf *)buf_data;
>> > tpm_buf_init(buf, sizeof(buf_data));
>> >
>> > Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>
>> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...nsys.com>
>> > ---
>> > v3:
>> > - A new patch from the earlier series with more scoped changes and
>> > less abstract commit message.
>> > ---
>> > drivers/char/tpm/tpm-buf.c | 122 +++++----
>> > drivers/char/tpm/tpm-sysfs.c | 20 +-
>> > drivers/char/tpm/tpm.h | 1 -
>> > drivers/char/tpm/tpm1-cmd.c | 147 +++++------
>> > drivers/char/tpm/tpm2-cmd.c | 290 ++++++++++------------
>> > drivers/char/tpm/tpm2-sessions.c | 121 +++++----
>> > drivers/char/tpm/tpm2-space.c | 44 ++--
>> > drivers/char/tpm/tpm_vtpm_proxy.c | 30 +--
>> > include/linux/tpm.h | 18 +-
>> > security/keys/trusted-keys/trusted_tpm1.c | 34 ++-
>> > security/keys/trusted-keys/trusted_tpm2.c | 176 ++++++-------
>> > 11 files changed, 482 insertions(+), 521 deletions(-)
>> >
>> > diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
>> > index c9e6e5d097ca..1cb649938c01 100644
>> > --- a/drivers/char/tpm/tpm-buf.c
>> > +++ b/drivers/char/tpm/tpm-buf.c
>> > @@ -7,82 +7,109 @@
>> > #include <linux/module.h>
>> > #include <linux/tpm.h>
>> >
>> > -/**
>> > - * tpm_buf_init() - Allocate and initialize a TPM command
>> > - * @buf: A &tpm_buf
>> > - * @tag: TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
>> > - * @ordinal: A command ordinal
>> > - *
>> > - * Return: 0 or -ENOMEM
>> > - */
>> > -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
>> > +static void __tpm_buf_size_invariant(struct tpm_buf *buf, u16 buf_size)
>> > {
>> > - buf->data = (u8 *)__get_free_page(GFP_KERNEL);
>> > - if (!buf->data)
>> > - return -ENOMEM;
>> > -
>> > - tpm_buf_reset(buf, tag, ordinal);
>> > - return 0;
>> > + u32 buf_size_2 = (u32)buf->capacity + (u32)sizeof(*buf);
>> > +
>> > + if (!buf->capacity) {
>> > + if (buf_size > TPM_BUFSIZE) {
>> > + WARN(1, "%s: size overflow: %u\n", __func__, buf_size);
>> > + buf->flags |= TPM_BUF_INVALID;
>> > + }
>> > + } else {
>> > + if (buf_size != buf_size_2) {
>> > + WARN(1, "%s: size mismatch: %u != %u\n", __func__, buf_size,
>> > + buf_size_2);
>> > + buf->flags |= TPM_BUF_INVALID;
>> > + }
>> > + }
>> > }
>> > -EXPORT_SYMBOL_GPL(tpm_buf_init);
>> >
>> > -/**
>> > - * tpm_buf_reset() - Initialize a TPM command
>> > - * @buf: A &tpm_buf
>> > - * @tag: TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
>> > - * @ordinal: A command ordinal
>> > - */
>> > -void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>> > +static void __tpm_buf_reset(struct tpm_buf *buf, u16 buf_size, u16 tag, u32 ordinal)
>> > {
>> > struct tpm_header *head = (struct tpm_header *)buf->data;
>> >
>> > + __tpm_buf_size_invariant(buf, buf_size);
>> > +
>> > + if (buf->flags & TPM_BUF_INVALID)
>> > + return;
>> > +
>> > WARN_ON(tag != TPM_TAG_RQU_COMMAND && tag != TPM2_ST_NO_SESSIONS &&
>> > tag != TPM2_ST_SESSIONS && tag != 0);
>> >
>> > buf->flags = 0;
>> > buf->length = sizeof(*head);
>> > + buf->capacity = buf_size - sizeof(*buf);
>> > + buf->handles = 0;
>> > head->tag = cpu_to_be16(tag);
>> > head->length = cpu_to_be32(sizeof(*head));
>> > head->ordinal = cpu_to_be32(ordinal);
>> > +}
>> > +
>> > +static void __tpm_buf_reset_sized(struct tpm_buf *buf, u16 buf_size)
>> > +{
>> > + __tpm_buf_size_invariant(buf, buf_size);
>> > +
>> > + if (buf->flags & TPM_BUF_INVALID)
>> > + return;
>> > +
>> > + buf->flags = TPM_BUF_TPM2B;
>> > + buf->length = 2;
>> > + buf->capacity = buf_size - sizeof(*buf);
>> > buf->handles = 0;
>> > + buf->data[0] = 0;
>> > + buf->data[1] = 0;
>> > }
>> > -EXPORT_SYMBOL_GPL(tpm_buf_reset);
>> >
>> > /**
>> > - * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
>> > - * @buf: A @tpm_buf
>> > - *
>> > - * Return: 0 or -ENOMEM
>> > + * tpm_buf_init() - Initialize a TPM command
>> > + * @buf: A &tpm_buf
>> > + * @buf_size: Size of the buffer.
>> > */
>> > -int tpm_buf_init_sized(struct tpm_buf *buf)
>> > +void tpm_buf_init(struct tpm_buf *buf, u16 buf_size)
>> > {
>> > - buf->data = (u8 *)__get_free_page(GFP_KERNEL);
>> > - if (!buf->data)
>> > - return -ENOMEM;
>> > + memset(buf, 0, buf_size);
>> > + __tpm_buf_reset(buf, buf_size, TPM_TAG_RQU_COMMAND, 0);
>> > +}
>> > +EXPORT_SYMBOL_GPL(tpm_buf_init);
>> >
>> > - tpm_buf_reset_sized(buf);
>> > - return 0;
>> > +/**
>> > + * tpm_buf_init_sized() - Initialize a sized buffer
>> > + * @buf: A &tpm_buf
>> > + * @buf_size: Size of the buffer.
>> > + */
>> > +void tpm_buf_init_sized(struct tpm_buf *buf, u16 buf_size)
>> > +{
>> > + memset(buf, 0, buf_size);
>> > + __tpm_buf_reset_sized(buf, buf_size);
>> > }
>> > EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
>> >
>> > /**
>> > - * tpm_buf_reset_sized() - Initialize a sized buffer
>> > + * tpm_buf_reset() - Re-initialize a TPM command
>> > * @buf: A &tpm_buf
>> > + * @tag: TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
>> > + * @ordinal: A command ordinal
>> > */
>> > -void tpm_buf_reset_sized(struct tpm_buf *buf)
>> > +void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>> > {
>> > - buf->flags = TPM_BUF_TPM2B;
>> > - buf->length = 2;
>> > - buf->data[0] = 0;
>> > - buf->data[1] = 0;
>> > + u16 buf_size = buf->capacity + sizeof(*buf);
>> > +
>> > + __tpm_buf_reset(buf, buf_size, tag, ordinal);
>> > }
>> > -EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
>> > +EXPORT_SYMBOL_GPL(tpm_buf_reset);
>> >
>> > -void tpm_buf_destroy(struct tpm_buf *buf)
>> > +/**
>> > + * tpm_buf_reset_sized() - Re-initialize a sized buffer
>> > + * @buf: A &tpm_buf
>> > + */
>> > +void tpm_buf_reset_sized(struct tpm_buf *buf)
>> > {
>> > - free_page((unsigned long)buf->data);
>> > + u16 buf_size = buf->capacity + sizeof(*buf);
>> > +
>> > + __tpm_buf_reset_sized(buf, buf_size);
>> > }
>> > -EXPORT_SYMBOL_GPL(tpm_buf_destroy);
>> > +EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
>> >
>> > /**
>> > * tpm_buf_length() - Return the number of bytes consumed by the data
>> > @@ -92,6 +119,9 @@ EXPORT_SYMBOL_GPL(tpm_buf_destroy);
>> > */
>> > u32 tpm_buf_length(struct tpm_buf *buf)
>>
>> Should we update the return value to u16?
>>
>> > {
>> > + if (buf->flags & TPM_BUF_INVALID)
>> > + return 0;
>> > +
>> > return buf->length;
>> > }
>> > EXPORT_SYMBOL_GPL(tpm_buf_length);
>> > @@ -104,10 +134,12 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
>> > */
>> > void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
>> > {
>> > + u32 total_length = (u32)buf->length + (u32)new_length;
>> > +
>> > if (buf->flags & TPM_BUF_INVALID)
>> > return;
>> >
>> > - if ((buf->length + new_length) > PAGE_SIZE) {
>> > + if (total_length > (u32)buf->capacity) {
>> > WARN(1, "tpm_buf: write overflow\n");
>> > buf->flags |= TPM_BUF_INVALID;
>> > return;
>>
>> [...]
>>
>> > diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
>> > index 636acb66a4f6..6e6a9fb48e63 100644
>> > --- a/security/keys/trusted-keys/trusted_tpm1.c
>> > +++ b/security/keys/trusted-keys/trusted_tpm1.c
>> > @@ -310,9 +310,8 @@ static int TSS_checkhmac2(unsigned char *buffer,
>> > * For key specific tpm requests, we will generate and send our
>> > * own TPM command packets using the drivers send function.
>> > */
>> > -static int trusted_tpm_send(unsigned char *cmd, size_t buflen)
>> > +static int trusted_tpm_send(void *cmd, size_t buflen)
>> > {
>> > - struct tpm_buf buf;
>> > int rc;
>> >
>> > if (!chip)
>> > @@ -322,15 +321,12 @@ static int trusted_tpm_send(unsigned char *cmd, size_t buflen)
>> > if (rc)
>> > return rc;
>> >
>> > - buf.flags = 0;
>> > - buf.length = buflen;
>> > - buf.data = cmd;
>> > dump_tpm_buf(cmd);
>> > - rc = tpm_transmit_cmd(chip, &buf, 4, "sending data");
>> > + rc = tpm_transmit_cmd(chip, cmd, 4, "sending data");
>>
>> Is it fine here to remove the intermediate tpm_buf ?
>>
>> IIUC tpm_transmit_cmd() needs a tpm_buf, while here we are passing just
>> the "data", or in some way it's a nested tpm_buf?
>>
>> (Sorry if it's a stupid question, but I'm still a bit new with this code).
>>
>> > dump_tpm_buf(cmd);
>> >
>> > + /* Convert TPM error to -EPERM. */
>> > if (rc > 0)
>> > - /* TPM error */
>> > rc = -EPERM;
>> >
>> > tpm_put_ops(chip);
>> > @@ -624,23 +620,23 @@ static int tpm_unseal(struct tpm_buf *tb,
>> > static int key_seal(struct trusted_key_payload *p,
>> > struct trusted_key_options *o)
>> > {
>> > - struct tpm_buf tb;
>> > int ret;
>> >
>> > - ret = tpm_buf_init(&tb, 0, 0);
>> > - if (ret)
>> > - return ret;
>> > + struct tpm_buf *tb __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
>> > + if (!tb)
>> > + return -ENOMEM;
>> > +
>> > + tpm_buf_init(tb, TPM_BUFSIZE);
>> >
>> > /* include migratable flag at end of sealed key */
>> > p->key[p->key_len] = p->migratable;
>> >
>> > - ret = tpm_seal(&tb, o->keytype, o->keyhandle, o->keyauth,
>> > + ret = tpm_seal(tb, o->keytype, o->keyhandle, o->keyauth,
>> > p->key, p->key_len + 1, p->blob, &p->blob_len,
>> > o->blobauth, o->pcrinfo, o->pcrinfo_len);
>> > if (ret < 0)
>> > pr_info("srkseal failed (%d)\n", ret);
>> >
>> > - tpm_buf_destroy(&tb);
>> > return ret;
>> > }
>> >
>> > @@ -650,14 +646,15 @@ static int key_seal(struct trusted_key_payload *p,
>> > static int key_unseal(struct trusted_key_payload *p,
>> > struct trusted_key_options *o)
>> > {
>> > - struct tpm_buf tb;
>> > int ret;
>> >
>> > - ret = tpm_buf_init(&tb, 0, 0);
>> > - if (ret)
>> > - return ret;
>> > + struct tpm_buf *tb __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
>> > + if (!tb)
>> > + return -ENOMEM;
>> > +
>> > + tpm_buf_init(tb, TPM_BUFSIZE);
>> >
>> > - ret = tpm_unseal(&tb, o->keyhandle, o->keyauth, p->blob, p->blob_len,
>> > + ret = tpm_unseal(tb, o->keyhandle, o->keyauth, p->blob, p->blob_len,
>> > o->blobauth, p->key, &p->key_len);
>> > if (ret < 0)
>> > pr_info("srkunseal failed (%d)\n", ret);
>> > @@ -665,7 +662,6 @@ static int key_unseal(struct trusted_key_payload *p,
>> > /* pull migratable flag out of sealed key */
>> > p->migratable = p->key[--p->key_len];
>> >
>> > - tpm_buf_destroy(&tb);
>> > return ret;
>> > }
>>
>> The rest LGTM, but it's a huge patch (not your issue at all), so yeah not
>> sure :-)
>
>It's still a single logical change :-)
Yep, and good set of patches to prepare this!
BTW I'm still bit concerned about the changes in trusted_tpm_send()
which I left a few lines above, can you check it?
Thanks,
Stefano
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