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Message-ID: <u7zay2gb3dff4ptbh34qw7ini63ar3246ivd4xnxtdxc6ijktx@lutatpeg7f7z>
Date: Tue, 30 Sep 2025 14:44:52 +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 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)
> 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 :-)
Thanks,
Stefano
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