[PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jarkko Sakkinen]

From: James Bottomley <James.Bottomley@HansenPartnership.com>

separate out the tpm_buf_... handling functions from static inlines in
tpm.h and move them to their own tpm-buf.c file.  This is a precursor
to adding new functions for other TPM type handling because the amount
of code will grow from the current 70 lines in tpm.h to about 200
lines when the additions are done.  200 lines of inline functions is a
bit too much to keep in a header file.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v3: make tpm_buf_tag static
v4: remove space after spdx tag
v5: fix checkpatch.pl --strict issues
---
 drivers/char/tpm/Makefile  |  1 +
 drivers/char/tpm/tpm-buf.c | 87 ++++++++++++++++++++++++++++++++++++++
 include/linux/tpm.h        | 86 ++++---------------------------------
 3 files changed, 97 insertions(+), 77 deletions(-)
 create mode 100644 drivers/char/tpm/tpm-buf.c

diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 0222b1ddb310..ad3594e383e1 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -15,6 +15,7 @@ tpm-y += tpm-sysfs.o
 tpm-y += eventlog/common.o
 tpm-y += eventlog/tpm1.o
 tpm-y += eventlog/tpm2.o
+tpm-y += tpm-buf.o
 
 tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
 tpm-$(CONFIG_EFI) += eventlog/efi.o
diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
new file mode 100644
index 000000000000..88ce1a5402de
--- /dev/null
+++ b/drivers/char/tpm/tpm-buf.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Handing for tpm_buf structures to facilitate the building of commands
+ */
+
+#include <linux/module.h>
+#include <linux/tpm.h>
+
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+	if (!buf->data)
+		return -ENOMEM;
+
+	buf->flags = 0;
+	tpm_buf_reset(buf, tag, ordinal);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_init);
+
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	head->tag = cpu_to_be16(tag);
+	head->length = cpu_to_be32(sizeof(*head));
+	head->ordinal = cpu_to_be32(ordinal);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_reset);
+
+void tpm_buf_destroy(struct tpm_buf *buf)
+{
+	free_page((unsigned long)buf->data);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_destroy);
+
+u32 tpm_buf_length(struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+
+	return be32_to_cpu(head->length);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_length);
+
+void tpm_buf_append(struct tpm_buf *buf,
+		    const unsigned char *new_data,
+		    unsigned int new_len)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	u32 len = tpm_buf_length(buf);
+
+	/* Return silently if overflow has already happened. */
+	if (buf->flags & TPM_BUF_OVERFLOW)
+		return;
+
+	if ((len + new_len) > PAGE_SIZE) {
+		WARN(1, "tpm_buf: overflow\n");
+		buf->flags |= TPM_BUF_OVERFLOW;
+		return;
+	}
+
+	memcpy(&buf->data[len], new_data, new_len);
+	head->length = cpu_to_be32(len + new_len);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append);
+
+void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value)
+{
+	tpm_buf_append(buf, &value, 1);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u8);
+
+void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value)
+{
+	__be16 value2 = cpu_to_be16(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 2);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u16);
+
+void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
+{
+	__be32 value2 = cpu_to_be32(value);
+
+	tpm_buf_append(buf, (u8 *)&value2, 4);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 4ee9d13749ad..60032c60994b 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -326,84 +326,16 @@ struct tpm2_hash {
 	unsigned int tpm_id;
 };
 
-static inline void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	head->tag = cpu_to_be16(tag);
-	head->length = cpu_to_be32(sizeof(*head));
-	head->ordinal = cpu_to_be32(ordinal);
-}
-
-static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
-{
-	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
-	if (!buf->data)
-		return -ENOMEM;
-
-	buf->flags = 0;
-	tpm_buf_reset(buf, tag, ordinal);
-	return 0;
-}
-
-static inline void tpm_buf_destroy(struct tpm_buf *buf)
-{
-	free_page((unsigned long)buf->data);
-}
-
-static inline u32 tpm_buf_length(struct tpm_buf *buf)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be32_to_cpu(head->length);
-}
-
-static inline u16 tpm_buf_tag(struct tpm_buf *buf)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be16_to_cpu(head->tag);
-}
-
-static inline void tpm_buf_append(struct tpm_buf *buf,
-				  const unsigned char *new_data,
-				  unsigned int new_len)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-	u32 len = tpm_buf_length(buf);
-
-	/* Return silently if overflow has already happened. */
-	if (buf->flags & TPM_BUF_OVERFLOW)
-		return;
-
-	if ((len + new_len) > PAGE_SIZE) {
-		WARN(1, "tpm_buf: overflow\n");
-		buf->flags |= TPM_BUF_OVERFLOW;
-		return;
-	}
 
-	memcpy(&buf->data[len], new_data, new_len);
-	head->length = cpu_to_be32(len + new_len);
-}
-
-static inline void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value)
-{
-	tpm_buf_append(buf, &value, 1);
-}
-
-static inline void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value)
-{
-	__be16 value2 = cpu_to_be16(value);
-
-	tpm_buf_append(buf, (u8 *) &value2, 2);
-}
-
-static inline void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
-{
-	__be32 value2 = cpu_to_be32(value);
-
-	tpm_buf_append(buf, (u8 *) &value2, 4);
-}
+int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
+void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
+void tpm_buf_destroy(struct tpm_buf *buf);
+u32 tpm_buf_length(struct tpm_buf *buf);
+void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
+		    unsigned int new_len);
+void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
+void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
+void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.42.0

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jerry Snitselaar]

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jarkko Sakkinen]

On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
>

Thanks I'll add it to the next round.

For the tpm_buf_read(), I was thinking along the lines of:

/**
 * tpm_buf_read() - Read from a TPM buffer
 * @buf:	&tpm_buf instance
 * @pos:	position within the buffer
 * @count:	the number of bytes to read
 * @output:	the output buffer
 *
 * Read bytes from a TPM buffer, and update the position. Returns false when the
 * amount of bytes requested would overflow the buffer, which is expected to
 * only happen in the case of hardware failure.
 */
static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos, size_t count, void *output)
{
	off_t next = *pos + count;

	if (next >= buf->length) {
		pr_warn("%s: %lu >= %lu\n", __func__, next, *offset);
		return false;
	}

	memcpy(output, &buf->data[*pos], count);
	*offset = next;
	return true;
}

BR, Jarkko

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jerry Snitselaar]

On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> 
> On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> >
> 
> Thanks I'll add it to the next round.
> 
> For the tpm_buf_read(), I was thinking along the lines of:
> 
> /**
>  * tpm_buf_read() - Read from a TPM buffer
>  * @buf:	&tpm_buf instance
>  * @pos:	position within the buffer
>  * @count:	the number of bytes to read
>  * @output:	the output buffer
>  *
>  * Read bytes from a TPM buffer, and update the position. Returns false when the
>  * amount of bytes requested would overflow the buffer, which is expected to
>  * only happen in the case of hardware failure.
>  */
> static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos, size_t count, void *output)
> {
> 	off_t next = *pos + count;
> 
> 	if (next >= buf->length) {
> 		pr_warn("%s: %lu >= %lu\n", __func__, next, *offset);
> 		return false;
> 	}
> 
> 	memcpy(output, &buf->data[*pos], count);
> 	*offset = next;
> 	return true;
> }
> 
> BR, Jarkko
> 

Then the callers will check, and return -EIO?

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[James Bottomley]

On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > 
> > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > 
> > 
> > Thanks I'll add it to the next round.
> > 
> > For the tpm_buf_read(), I was thinking along the lines of:
> > 
> > /**
> >  * tpm_buf_read() - Read from a TPM buffer
> >  * @buf:        &tpm_buf instance
> >  * @pos:        position within the buffer
> >  * @count:      the number of bytes to read
> >  * @output:     the output buffer
> >  *
> >  * Read bytes from a TPM buffer, and update the position. Returns
> > false when the
> >  * amount of bytes requested would overflow the buffer, which is
> > expected to
> >  * only happen in the case of hardware failure.
> >  */
> > static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos,
> > size_t count, void *output)
> > {
> >         off_t next = *pos + count;
> > 
> >         if (next >= buf->length) {
> >                 pr_warn("%s: %lu >= %lu\n", __func__, next,
> > *offset);
> >                 return false;
> >         }
> > 
> >         memcpy(output, &buf->data[*pos], count);
> >         *offset = next;
> >         return true;
> > }
> > 
> > BR, Jarkko
> > 
> 
> Then the callers will check, and return -EIO?

Really, no, why would we do that?

The initial buffer is a page and no TPM currently can have a command
that big, so if the buffer overflows, it's likely a programming error
(failure to terminate loop or something) rather than a runtime one (a
user actually induced a command that big and wanted it to be sent to
the TPM).  The only reason you might need to check is the no-alloc case
and you passed in a much smaller buffer, but even there, I would guess
it will come down to a coding fault not a possible runtime error.

James

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jerry Snitselaar]

On Thu, Oct 26, 2023 at 01:55:55PM -0400, James Bottomley wrote:
> On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> > On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> > > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > 
> > > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > 
> > > 
> > > Thanks I'll add it to the next round.
> > > 
> > > For the tpm_buf_read(), I was thinking along the lines of:
> > > 
> > > /**
> > >  * tpm_buf_read() - Read from a TPM buffer
> > >  * @buf:        &tpm_buf instance
> > >  * @pos:        position within the buffer
> > >  * @count:      the number of bytes to read
> > >  * @output:     the output buffer
> > >  *
> > >  * Read bytes from a TPM buffer, and update the position. Returns
> > > false when the
> > >  * amount of bytes requested would overflow the buffer, which is
> > > expected to
> > >  * only happen in the case of hardware failure.
> > >  */
> > > static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos,
> > > size_t count, void *output)
> > > {
> > >         off_t next = *pos + count;
> > > 
> > >         if (next >= buf->length) {
> > >                 pr_warn("%s: %lu >= %lu\n", __func__, next,
> > > *offset);
> > >                 return false;
> > >         }
> > > 
> > >         memcpy(output, &buf->data[*pos], count);
> > >         *offset = next;
> > >         return true;
> > > }
> > > 
> > > BR, Jarkko
> > > 
> > 
> > Then the callers will check, and return -EIO?
> 
> Really, no, why would we do that?
> 
> The initial buffer is a page and no TPM currently can have a command
> that big, so if the buffer overflows, it's likely a programming error
> (failure to terminate loop or something) rather than a runtime one (a
> user actually induced a command that big and wanted it to be sent to
> the TPM).  The only reason you might need to check is the no-alloc case
> and you passed in a much smaller buffer, but even there, I would guess
> it will come down to a coding fault not a possible runtime error.
> 
> James
> 

I was clarifying based on this exchange below between Jarkko and Mario discussing patch 5/6.
From https://lore.kernel.org/all/CWGM2YH00DJ3.JKSYNNEWVRW4@suppilovahvero/ :


> > In the overflow case wouldn't you want to pass an error code up instead 
> > of just showing a WARN trace?
> >
> > The helper functions can't tell the difference, and the net outcome is 
> > going to be that if there is overflow you get a warning trace in the 
> > kernel log and whatever garbage "value" happened to have going to the 
> > caller.  It's a programmer error but it's also unpredictable what 
> > happens here.
> >
> > I think it's cleaner to have callers of 
> > tpm_buf_read_u8/tpm_buf_read_u16/tpm_buf_read_u32 to to be able to know 
> > something wrong happened.
>
> I think you have a fair point here and I also think it is also a bigger
> issue for the response parsing than programmer error. I.e. faulty or
> malicious TPM could return corrupted data, which makes WARN() wrong
> choice.
>
> So, as a corrective measure I think it should be pr_warn() instead, and
> instead of returning u8/u16/u32, all functions should return 'ssize_t'
> and -EIO in the case of overflow.
>
> Thank you, it was a really good catch.
>
> BR, Jarkko

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jarkko Sakkinen]

On Thu, 2023-10-26 at 13:55 -0400, James Bottomley wrote:
> On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> > On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> > > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > 
> > > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > 
> > > 
> > > Thanks I'll add it to the next round.
> > > 
> > > For the tpm_buf_read(), I was thinking along the lines of:
> > > 
> > > /**
> > >  * tpm_buf_read() - Read from a TPM buffer
> > >  * @buf:        &tpm_buf instance
> > >  * @pos:        position within the buffer
> > >  * @count:      the number of bytes to read
> > >  * @output:     the output buffer
> > >  *
> > >  * Read bytes from a TPM buffer, and update the position. Returns
> > > false when the
> > >  * amount of bytes requested would overflow the buffer, which is
> > > expected to
> > >  * only happen in the case of hardware failure.
> > >  */
> > > static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos,
> > > size_t count, void *output)
> > > {
> > >         off_t next = *pos + count;
> > > 
> > >         if (next >= buf->length) {
> > >                 pr_warn("%s: %lu >= %lu\n", __func__, next,
> > > *offset);
> > >                 return false;
> > >         }
> > > 
> > >         memcpy(output, &buf->data[*pos], count);
> > >         *offset = next;
> > >         return true;
> > > }
> > > 
> > > BR, Jarkko
> > > 
> > 
> > Then the callers will check, and return -EIO?
> 
> Really, no, why would we do that?
> 
> The initial buffer is a page and no TPM currently can have a command
> that big, so if the buffer overflows, it's likely a programming error
> (failure to terminate loop or something) rather than a runtime one (a
> user actually induced a command that big and wanted it to be sent to
> the TPM).  The only reason you might need to check is the no-alloc case
> and you passed in a much smaller buffer, but even there, I would guess
> it will come down to a coding fault not a possible runtime error.


Yeah, this was my thinking too. So in HMAC case you anyway would not
need to check it because crypto is destined to fail anyway.

Returning boolean here does no harm so I thought that this is overally
good compromise.

BR, Jarkko

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jarkko Sakkinen]

On Sun, 2023-11-05 at 23:59 +0200, Jarkko Sakkinen wrote:
> On Thu, 2023-10-26 at 13:55 -0400, James Bottomley wrote:
> > On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> > > On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> > > > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > 
> > > > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > > 
> > > > 
> > > > Thanks I'll add it to the next round.
> > > > 
> > > > For the tpm_buf_read(), I was thinking along the lines of:
> > > > 
> > > > /**
> > > >  * tpm_buf_read() - Read from a TPM buffer
> > > >  * @buf:        &tpm_buf instance
> > > >  * @pos:        position within the buffer
> > > >  * @count:      the number of bytes to read
> > > >  * @output:     the output buffer
> > > >  *
> > > >  * Read bytes from a TPM buffer, and update the position. Returns
> > > > false when the
> > > >  * amount of bytes requested would overflow the buffer, which is
> > > > expected to
> > > >  * only happen in the case of hardware failure.
> > > >  */
> > > > static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos,
> > > > size_t count, void *output)
> > > > {
> > > >         off_t next = *pos + count;
> > > > 
> > > >         if (next >= buf->length) {
> > > >                 pr_warn("%s: %lu >= %lu\n", __func__, next,
> > > > *offset);
> > > >                 return false;
> > > >         }
> > > > 
> > > >         memcpy(output, &buf->data[*pos], count);
> > > >         *offset = next;
> > > >         return true;
> > > > }
> > > > 
> > > > BR, Jarkko
> > > > 
> > > 
> > > Then the callers will check, and return -EIO?
> > 
> > Really, no, why would we do that?
> > 
> > The initial buffer is a page and no TPM currently can have a command
> > that big, so if the buffer overflows, it's likely a programming error
> > (failure to terminate loop or something) rather than a runtime one (a
> > user actually induced a command that big and wanted it to be sent to
> > the TPM).  The only reason you might need to check is the no-alloc case
> > and you passed in a much smaller buffer, but even there, I would guess
> > it will come down to a coding fault not a possible runtime error.
> 
> 
> Yeah, this was my thinking too. So in HMAC case you anyway would not
> need to check it because crypto is destined to fail anyway.
> 
> Returning boolean here does no harm so I thought that this is overally
> good compromise.

Or actually maybe we should go just with void, as it does have even
then "return value", as it emits to klog, right?

BR, Jarkko

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[James Bottomley]

On Mon, 2023-11-06 at 00:01 +0200, Jarkko Sakkinen wrote:
> On Sun, 2023-11-05 at 23:59 +0200, Jarkko Sakkinen wrote:
> > On Thu, 2023-10-26 at 13:55 -0400, James Bottomley wrote:
> > > On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> > > > On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen
> > > > wrote:
> > > > > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > > 
> > > > > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > > > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > > > > 
> > > > > 
> > > > > Thanks I'll add it to the next round.
> > > > > 
> > > > > For the tpm_buf_read(), I was thinking along the lines of:
> > > > > 
> > > > > /**
> > > > >  * tpm_buf_read() - Read from a TPM buffer
> > > > >  * @buf:        &tpm_buf instance
> > > > >  * @pos:        position within the buffer
> > > > >  * @count:      the number of bytes to read
> > > > >  * @output:     the output buffer
> > > > >  *
> > > > >  * Read bytes from a TPM buffer, and update the position.
> > > > > Returns
> > > > > false when the
> > > > >  * amount of bytes requested would overflow the buffer, which
> > > > > is
> > > > > expected to
> > > > >  * only happen in the case of hardware failure.
> > > > >  */
> > > > > static bool tpm_buf_read(const struct tpm_buf *buf, off_t
> > > > > *pos,
> > > > > size_t count, void *output)
> > > > > {
> > > > >         off_t next = *pos + count;
> > > > > 
> > > > >         if (next >= buf->length) {
> > > > >                 pr_warn("%s: %lu >= %lu\n", __func__, next,
> > > > > *offset);
> > > > >                 return false;
> > > > >         }
> > > > > 
> > > > >         memcpy(output, &buf->data[*pos], count);
> > > > >         *offset = next;
> > > > >         return true;
> > > > > }
> > > > > 
> > > > > BR, Jarkko
> > > > > 
> > > > 
> > > > Then the callers will check, and return -EIO?
> > > 
> > > Really, no, why would we do that?
> > > 
> > > The initial buffer is a page and no TPM currently can have a
> > > command that big, so if the buffer overflows, it's likely a
> > > programming error (failure to terminate loop or something) rather
> > > than a runtime one (a user actually induced a command that big
> > > and wanted it to be sent to the TPM).  The only reason you might
> > > need to check is the no-alloc case and you passed in a much
> > > smaller buffer, but even there, I would guess it will come down
> > > to a coding fault not a possible runtime error.
> > 
> > 
> > Yeah, this was my thinking too. So in HMAC case you anyway would
> > not need to check it because crypto is destined to fail anyway.
> > 
> > Returning boolean here does no harm so I thought that this is
> > overally good compromise.
> 
> Or actually maybe we should go just with void, as it does have even
> then "return value", as it emits to klog, right?

Right, these functions are almost drop in replacements for the
get_inc_XX ones.  The latter were void returning because all the
knowledge of what is being looked for is in the calling routine,
because it knows at a macro level what structure the buffer should
have.

James

Re: [PATCH v3 1/6] tpm: Move buffer handling from static inlines to real functions

[Jarkko Sakkinen]

On Thu, 2023-10-26 at 10:10 -0700, Jerry Snitselaar wrote:
> On Wed, Oct 25, 2023 at 08:35:55PM +0300, Jarkko Sakkinen wrote:
> > On Wed Oct 25, 2023 at 12:03 PM EEST, Jerry Snitselaar wrote:
> > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > 
> > On Wed, 2023-10-25 at 02:03 -0700, Jerry Snitselaar wrote:
> > > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> > > 
> > 
> > Thanks I'll add it to the next round.
> > 
> > For the tpm_buf_read(), I was thinking along the lines of:
> > 
> > /**
> >  * tpm_buf_read() - Read from a TPM buffer
> >  * @buf: &tpm_buf instance
> >  * @pos: position within the buffer
> >  * @count: the number of bytes to read
> >  * @output: the output buffer
> >  *
> >  * Read bytes from a TPM buffer, and update the position. Returns false when the
> >  * amount of bytes requested would overflow the buffer, which is expected to
> >  * only happen in the case of hardware failure.
> >  */
> > static bool tpm_buf_read(const struct tpm_buf *buf, off_t *pos, size_t count, void *output)
> > {
> >  off_t next = *pos + count;
> > 
> >  if (next >= buf->length) {
> >  pr_warn("%s: %lu >= %lu\n", __func__, next, *offset);
> >  return false;
> >  }
> > 
> >  memcpy(output, &buf->data[*pos], count);
> >  *offset = next;
> >  return true;
> > }
> > 
> > BR, Jarkko
> > 
> 
> Then the callers will check, and return -EIO?

Most likely. My thinking with boolean was that this way it
sort of documents that this function can have only single
possible error state.

If it was int there could be possibly some other error codes
to handle...

Just would prefer this based on my experience calling other
in-kernel functions. I often need to use lxr a lot just to
get full understanding of all possible POSIX codes...

BR, Jarkko

[PATCH v3 2/6] tpm: Store TPM buffer length

[Jarkko Sakkinen]

Both TPM commands and sized buffers (TPM2B) have a fixed size header, which
is followed by the body. Store TPM buffer length to a new field in the
struct tpm_buf.

The invariant here is that the length field must always contain the total
length of the buffer, i.e. the sum header and body length. The value must
then be mapped to the length representation of the buffer type, and this
correspondence must be maintained.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm-buf.c                | 36 ++++++++++++++++-------
 drivers/char/tpm/tpm-interface.c          | 18 +++++++++---
 include/linux/tpm.h                       | 10 +++----
 security/keys/trusted-keys/trusted_tpm1.c |  8 ++---
 4 files changed, 49 insertions(+), 23 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 88ce1a5402de..8dc6b9db006b 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -18,6 +18,12 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 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)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
@@ -25,6 +31,8 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 	head->tag = cpu_to_be16(tag);
 	head->length = cpu_to_be32(sizeof(*head));
 	head->ordinal = cpu_to_be32(ordinal);
+
+	buf->length = sizeof(*head);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset);
 
@@ -34,33 +42,41 @@ void tpm_buf_destroy(struct tpm_buf *buf)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_destroy);
 
+/**
+ * tpm_buf_length() - Return the number of bytes consumed by the buffer
+ *
+ * Return: The number of bytes consumed by the buffer
+ */
 u32 tpm_buf_length(struct tpm_buf *buf)
 {
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
-	return be32_to_cpu(head->length);
+	return buf->length;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_length);
 
-void tpm_buf_append(struct tpm_buf *buf,
-		    const unsigned char *new_data,
-		    unsigned int new_len)
+/**
+ * tpm_buf_append() - Append data to an initialized buffer
+ * @buf:	A &tpm_buf
+ * @new_data:	A data blob
+ * @new_length:	Size of the appended data
+ */
+
+void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 {
 	struct tpm_header *head = (struct tpm_header *)buf->data;
-	u32 len = tpm_buf_length(buf);
 
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
 		return;
 
-	if ((len + new_len) > PAGE_SIZE) {
+	if ((buf->length + new_length) > PAGE_SIZE) {
 		WARN(1, "tpm_buf: overflow\n");
 		buf->flags |= TPM_BUF_OVERFLOW;
 		return;
 	}
 
-	memcpy(&buf->data[len], new_data, new_len);
-	head->length = cpu_to_be32(len + new_len);
+	memcpy(&buf->data[buf->length], new_data, new_length);
+	buf->length += new_length;
+	head->length = cpu_to_be32(buf->length);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append);
 
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 66b16d26eecc..492136214447 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -217,6 +217,9 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf,
 	int err;
 	ssize_t len;
 
+	/* The recorded length is expected to match the command length: */
+	WARN_ON(buf->length != be32_to_cpu(header->length));
+
 	len = tpm_transmit(chip, buf->data, PAGE_SIZE);
 	if (len <  0)
 		return len;
@@ -232,6 +235,11 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf,
 	if (len < min_rsp_body_length + TPM_HEADER_SIZE)
 		return -EFAULT;
 
+	buf->length = len;
+
+	/* The recorded length is expected to match the response length: */
+	WARN_ON(buf->length != be32_to_cpu(header->length));
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
@@ -345,12 +353,12 @@ EXPORT_SYMBOL_GPL(tpm_pcr_extend);
 /**
  * tpm_send - send a TPM command
  * @chip:	a &struct tpm_chip instance, %NULL for the default chip
- * @cmd:	a TPM command buffer
- * @buflen:	the length of the TPM command buffer
+ * @data:	command blob
+ * @cmdlen:	length of the command
  *
  * Return: same as with tpm_transmit_cmd()
  */
-int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
+int tpm_send(struct tpm_chip *chip, void *data, size_t length)
 {
 	struct tpm_buf buf;
 	int rc;
@@ -359,7 +367,9 @@ int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
 	if (!chip)
 		return -ENODEV;
 
-	buf.data = cmd;
+	buf.flags = 0;
+	buf.length = length;
+	buf.data = data;
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to a send a command");
 
 	tpm_put_ops(chip);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 60032c60994b..3cfe2aeb1d9a 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -307,7 +307,8 @@ enum tpm_buf_flags {
 };
 
 struct tpm_buf {
-	unsigned int flags;
+	u32 flags;
+	u16 length;
 	u8 *data;
 };
 
@@ -331,8 +332,7 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
-void tpm_buf_append(struct tpm_buf *buf, const unsigned char *new_data,
-		    unsigned int new_len);
+void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
 void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
 void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
 void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
@@ -361,7 +361,7 @@ extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 			struct tpm_digest *digest);
 extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 			  struct tpm_digest *digests);
-extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
+int tpm_send(struct tpm_chip *chip, void *data, size_t length);
 extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
 extern struct tpm_chip *tpm_default_chip(void);
 void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
@@ -382,7 +382,7 @@ static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	return -ENODEV;
 }
 
-static inline int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
+static inline int tpm_send(struct tpm_chip *chip, void *data, size_t length)
 {
 	return -ENODEV;
 }
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index aa108bea6739..7c1515014a5d 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -407,7 +407,7 @@ static int osap(struct tpm_buf *tb, struct osapsess *s,
 	tpm_buf_append_u32(tb, handle);
 	tpm_buf_append(tb, ononce, TPM_NONCE_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		return ret;
 
@@ -431,7 +431,7 @@ int oiap(struct tpm_buf *tb, uint32_t *handle, unsigned char *nonce)
 		return -ENODEV;
 
 	tpm_buf_reset(tb, TPM_TAG_RQU_COMMAND, TPM_ORD_OIAP);
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		return ret;
 
@@ -543,7 +543,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
 	tpm_buf_append_u8(tb, cont);
 	tpm_buf_append(tb, td->pubauth, SHA1_DIGEST_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0)
 		goto out;
 
@@ -634,7 +634,7 @@ static int tpm_unseal(struct tpm_buf *tb,
 	tpm_buf_append_u8(tb, cont);
 	tpm_buf_append(tb, authdata2, SHA1_DIGEST_SIZE);
 
-	ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+	ret = trusted_tpm_send(tb->data, tb->length);
 	if (ret < 0) {
 		pr_info("authhmac failed (%d)\n", ret);
 		return ret;
-- 
2.42.0

Re: [PATCH v3 2/6] tpm: Store TPM buffer length

[Jerry Snitselaar]

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Re: [PATCH v3 2/6] tpm: Store TPM buffer length

[Jarkko Sakkinen]

On Mon Nov 6, 2023 at 9:26 PM EET, Jerry Snitselaar wrote:
>
> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Thanks.

BR, Jarkko

Re: [PATCH v3 2/6] tpm: Store TPM buffer length

[Jerry Snitselaar]

On Tue, Oct 24, 2023 at 04:15:20AM +0300, Jarkko Sakkinen wrote:
> Both TPM commands and sized buffers (TPM2B) have a fixed size header, which
> is followed by the body. Store TPM buffer length to a new field in the
> struct tpm_buf.
> 
> The invariant here is that the length field must always contain the total
> length of the buffer, i.e. the sum header and body length. The value must
> then be mapped to the length representation of the buffer type, and this
> correspondence must be maintained.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
>  drivers/char/tpm/tpm-buf.c                | 36 ++++++++++++++++-------
>  drivers/char/tpm/tpm-interface.c          | 18 +++++++++---
>  include/linux/tpm.h                       | 10 +++----
>  security/keys/trusted-keys/trusted_tpm1.c |  8 ++---
>  4 files changed, 49 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index 88ce1a5402de..8dc6b9db006b 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -18,6 +18,12 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_init);
>  
> +/**
> + * tpm_buf_reset() - Initialize a TPM command
> + * @buf:	A @tpm_buf

One minor thing I meant to mention, did you intend this to be &tpm_buf like it
is for tpm_buf_append?

Regards,
Jerry

Re: [PATCH v3 2/6] tpm: Store TPM buffer length

[Jarkko Sakkinen]

On Mon Nov 6, 2023 at 9:36 PM EET, Jerry Snitselaar wrote:
> On Tue, Oct 24, 2023 at 04:15:20AM +0300, Jarkko Sakkinen wrote:
> > Both TPM commands and sized buffers (TPM2B) have a fixed size header, which
> > is followed by the body. Store TPM buffer length to a new field in the
> > struct tpm_buf.
> > 
> > The invariant here is that the length field must always contain the total
> > length of the buffer, i.e. the sum header and body length. The value must
> > then be mapped to the length representation of the buffer type, and this
> > correspondence must be maintained.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> >  drivers/char/tpm/tpm-buf.c                | 36 ++++++++++++++++-------
> >  drivers/char/tpm/tpm-interface.c          | 18 +++++++++---
> >  include/linux/tpm.h                       | 10 +++----
> >  security/keys/trusted-keys/trusted_tpm1.c |  8 ++---
> >  4 files changed, 49 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> > index 88ce1a5402de..8dc6b9db006b 100644
> > --- a/drivers/char/tpm/tpm-buf.c
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -18,6 +18,12 @@ int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> >  }
> >  EXPORT_SYMBOL_GPL(tpm_buf_init);
> >  
> > +/**
> > + * tpm_buf_reset() - Initialize a TPM command
> > + * @buf:	A @tpm_buf
>
> One minor thing I meant to mention, did you intend this to be &tpm_buf like it
> is for tpm_buf_append?

Yep, thanks. I'll change it to &tpm_buf.

BR, Jarkko

[PATCH v3 3/6] tpm: Detach tpm_buf_reset() from tpm_buf_init()

[Jarkko Sakkinen]

In order to use tpm_buf_init() for other buffer types, detach
tpm_buf_reset() from tpm_buf_init().

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm-buf.c                | 15 ++++++++--
 drivers/char/tpm/tpm-sysfs.c              |  3 +-
 drivers/char/tpm/tpm1-cmd.c               | 26 +++++++++++-----
 drivers/char/tpm/tpm2-cmd.c               | 36 ++++++++++++++++-------
 drivers/char/tpm/tpm2-space.c             |  7 +++--
 drivers/char/tpm/tpm_vtpm_proxy.c         | 13 ++++----
 include/linux/tpm.h                       |  2 +-
 security/keys/trusted-keys/trusted_tpm1.c |  4 +--
 security/keys/trusted-keys/trusted_tpm2.c |  9 ++++--
 9 files changed, 80 insertions(+), 35 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index 8dc6b9db006b..fa9a4c51157a 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -6,14 +6,25 @@
 #include <linux/module.h>
 #include <linux/tpm.h>
 
-int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+/**
+ * tpm_buf_init() - Initialize from the heap
+ * @buf:	A @tpm_buf
+ *
+ * Initialize all structure fields to zero, allocate a page from the heap, and
+ * zero the bytes that the buffer headers will consume.
+ *
+ * Return: 0 or -ENOMEM
+ */
+int tpm_buf_init(struct tpm_buf *buf)
 {
 	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
 	if (!buf->data)
 		return -ENOMEM;
 
 	buf->flags = 0;
-	tpm_buf_reset(buf, tag, ordinal);
+	buf->length = TPM_HEADER_SIZE;
+	memset(buf->data, 0, TPM_HEADER_SIZE);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(tpm_buf_init);
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 54c71473aa29..557e7f86d98d 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -44,9 +44,10 @@ static ssize_t pubek_show(struct device *dev, struct device_attribute *attr,
 	if (tpm_try_get_ops(chip))
 		return 0;
 
-	if (tpm_buf_init(&tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK))
+	if (tpm_buf_init(&tpm_buf))
 		goto out_ops;
 
+	tpm_buf_reset(&tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK);
 	tpm_buf_append(&tpm_buf, anti_replay, sizeof(anti_replay));
 
 	if (tpm_transmit_cmd(chip, &tpm_buf, READ_PUBEK_RESULT_MIN_BODY_SIZE,
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index cf64c7385105..28fea4e2daaf 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -328,10 +328,11 @@ static int tpm1_startup(struct tpm_chip *chip)
 
 	dev_info(&chip->dev, "starting up the TPM manually\n");
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
+	rc = tpm_buf_init(&buf);
 	if (rc < 0)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
 	tpm_buf_append_u16(&buf, TPM_ST_CLEAR);
 
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
@@ -466,10 +467,11 @@ int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);
 	tpm_buf_append_u32(&buf, pcr_idx);
 	tpm_buf_append(&buf, hash, TPM_DIGEST_SIZE);
 
@@ -485,10 +487,12 @@ ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
+
 	if (subcap_id == TPM_CAP_VERSION_1_1 ||
 	    subcap_id == TPM_CAP_VERSION_1_2) {
 		tpm_buf_append_u32(&buf, subcap_id);
@@ -537,10 +541,12 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	u32 recd;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
+
 	do {
 		tpm_buf_append_u32(&buf, num_bytes);
 
@@ -586,10 +592,11 @@ int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
 	tpm_buf_append_u32(&buf, pcr_idx);
 
 	rc = tpm_transmit_cmd(chip, &buf, TPM_DIGEST_SIZE,
@@ -622,10 +629,12 @@ static int tpm1_continue_selftest(struct tpm_chip *chip)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
+
 	rc = tpm_transmit_cmd(chip, &buf, 0, "continue selftest");
 	tpm_buf_destroy(&buf);
 	return rc;
@@ -752,9 +761,12 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
 		rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, dummy_hash,
 				     "extending dummy pcr before suspend");
 
-	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
+
+	tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
+
 	/* now do the actual savestate */
 	for (try = 0; try < TPM_RETRY; try++) {
 		rc = tpm_transmit_cmd(chip, &buf, 0, NULL);
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 93545be190a5..94dacbf74e0d 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -183,10 +183,12 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 		expected_digest_size = chip->allocated_banks[i].digest_size;
 	}
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
+
 	pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
 
 	tpm_buf_append_u32(&buf, 1);
@@ -240,10 +242,11 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	int rc;
 	int i;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
 	tpm_buf_append_u32(&buf, pcr_idx);
 
 	auth_area.handle = cpu_to_be32(TPM2_RS_PW);
@@ -299,7 +302,7 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	if (!num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	err = tpm_buf_init(&buf, 0, 0);
+	err = tpm_buf_init(&buf);
 	if (err)
 		return err;
 
@@ -350,13 +353,14 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
+	rc = tpm_buf_init(&buf);
 	if (rc) {
 		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
 			 handle);
 		return;
 	}
 
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
 	tpm_buf_append_u32(&buf, handle);
 
 	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
@@ -390,9 +394,11 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
+
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
 	tpm_buf_append_u32(&buf, TPM2_CAP_TPM_PROPERTIES);
 	tpm_buf_append_u32(&buf, property_id);
 	tpm_buf_append_u32(&buf, 1);
@@ -431,9 +437,11 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return;
+
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
 	tpm_buf_append_u16(&buf, shutdown_type);
 	tpm_transmit_cmd(chip, &buf, 0, "stopping the TPM");
 	tpm_buf_destroy(&buf);
@@ -459,10 +467,11 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
 	int rc;
 
 	for (full = 0; full < 2; full++) {
-		rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
+		rc = tpm_buf_init(&buf);
 		if (rc)
 			return rc;
 
+		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
 		tpm_buf_append_u8(&buf, full);
 		rc = tpm_transmit_cmd(chip, &buf, 0,
 				      "attempting the self test");
@@ -495,9 +504,11 @@ int tpm2_probe(struct tpm_chip *chip)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
+
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
 	tpm_buf_append_u32(&buf, TPM2_CAP_TPM_PROPERTIES);
 	tpm_buf_append_u32(&buf, TPM_PT_TOTAL_COMMANDS);
 	tpm_buf_append_u32(&buf, 1);
@@ -560,10 +571,11 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
 	int rc;
 	int i = 0;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
 	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
 	tpm_buf_append_u32(&buf, 0);
 	tpm_buf_append_u32(&buf, 1);
@@ -649,10 +661,11 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
 		goto out;
 	}
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		goto out;
 
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
 	tpm_buf_append_u32(&buf, TPM2_CAP_COMMANDS);
 	tpm_buf_append_u32(&buf, TPM2_CC_FIRST);
 	tpm_buf_append_u32(&buf, nr_commands);
@@ -711,10 +724,11 @@ static int tpm2_startup(struct tpm_chip *chip)
 
 	dev_info(&chip->dev, "starting up the TPM manually\n");
 
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
+	rc = tpm_buf_init(&buf);
 	if (rc < 0)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
 	tpm_buf_append_u16(&buf, TPM2_SU_CLEAR);
 	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
 	tpm_buf_destroy(&buf);
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 363afdd4d1d3..43584b4176d6 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -76,10 +76,12 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
 	unsigned int body_size;
 	int rc;
 
-	rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_LOAD);
+	rc = tpm_buf_init(&tbuf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_LOAD);
+
 	ctx = (struct tpm2_context *)&buf[*offset];
 	body_size = sizeof(*ctx) + be16_to_cpu(ctx->blob_size);
 	tpm_buf_append(&tbuf, &buf[*offset], body_size);
@@ -126,10 +128,11 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
 	unsigned int body_size;
 	int rc;
 
-	rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
+	rc = tpm_buf_init(&tbuf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
 	tpm_buf_append_u32(&tbuf, handle);
 
 	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
index 30e953988cab..b2b9a15a4a59 100644
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
@@ -399,14 +399,15 @@ static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
 	const struct tpm_header *header;
 	struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
 
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
-				  TPM2_CC_SET_LOCALITY);
-	else
-		rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
-				  TPM_ORD_SET_LOCALITY);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_SET_LOCALITY);
+	else
+		tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SET_LOCALITY);
+
 	tpm_buf_append_u8(&buf, locality);
 
 	proxy_dev->state |= STATE_DRIVER_COMMAND;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 3cfe2aeb1d9a..c355597351c6 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -328,7 +328,7 @@ struct tpm2_hash {
 };
 
 
-int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
+int tpm_buf_init(struct tpm_buf *buf);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index 7c1515014a5d..fcf0eef79ba0 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -664,7 +664,7 @@ static int key_seal(struct trusted_key_payload *p,
 	struct tpm_buf tb;
 	int ret;
 
-	ret = tpm_buf_init(&tb, 0, 0);
+	ret = tpm_buf_init(&tb);
 	if (ret)
 		return ret;
 
@@ -690,7 +690,7 @@ static int key_unseal(struct trusted_key_payload *p,
 	struct tpm_buf tb;
 	int ret;
 
-	ret = tpm_buf_init(&tb, 0, 0);
+	ret = tpm_buf_init(&tb);
 	if (ret)
 		return ret;
 
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index bc700f85f80b..c54659d06dcb 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -252,12 +252,13 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		return rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
+	rc = tpm_buf_init(&buf);
 	if (rc) {
 		tpm_put_ops(chip);
 		return rc;
 	}
 
+	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	tpm_buf_append_u32(&buf, options->keyhandle);
 	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
 			     NULL /* nonce */, 0,
@@ -409,10 +410,11 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
 	tpm_buf_append_u32(&buf, options->keyhandle);
 	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
 			     NULL /* nonce */, 0,
@@ -465,10 +467,11 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u8 *data;
 	int rc;
 
-	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+	rc = tpm_buf_init(&buf);
 	if (rc)
 		return rc;
 
+	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
 	tpm_buf_append_u32(&buf, blob_handle);
 	tpm2_buf_append_auth(&buf,
 			     options->policyhandle ?
-- 
2.42.0

Re: [PATCH v3 3/6] tpm: Detach tpm_buf_reset() from tpm_buf_init()

[Jerry Snitselaar]

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Re: [PATCH v3 3/6] tpm: Detach tpm_buf_reset() from tpm_buf_init()

[Jarkko Sakkinen]

On Mon Nov 6, 2023 at 9:31 PM EET, Jerry Snitselaar wrote:
> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

Thanks.

BR, Jarkko

[PATCH v3 4/6] tpm: Support TPM2 sized buffers (TPM2B)

[Jarkko Sakkinen]

Add boolean parameters @alloc and @sized to tpm_buf_init():

* If @alloc is set to false, buf->data is assumed to be pre-feeded and
  owned by the caller.
* If @sized is set to true, the buffer represents a sized buffer
  (TPM2B).

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm-buf.c                | 32 ++++++++++++++++-------
 drivers/char/tpm/tpm-sysfs.c              |  2 +-
 drivers/char/tpm/tpm1-cmd.c               | 14 +++++-----
 drivers/char/tpm/tpm2-cmd.c               | 22 ++++++++--------
 drivers/char/tpm/tpm2-space.c             |  4 +--
 drivers/char/tpm/tpm_vtpm_proxy.c         |  2 +-
 include/linux/tpm.h                       |  3 ++-
 security/keys/trusted-keys/trusted_tpm1.c |  4 +--
 security/keys/trusted-keys/trusted_tpm2.c |  6 ++---
 9 files changed, 51 insertions(+), 38 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index fa9a4c51157a..f1d92d7e758d 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -7,22 +7,32 @@
 #include <linux/tpm.h>
 
 /**
- * tpm_buf_init() - Initialize from the heap
+ * tpm_buf_init() - Initialize a TPM buffer
  * @buf:	A @tpm_buf
+ * @sized:	Represent a sized buffer (TPM2B)
+ * @alloc:	Allocate from the heap
  *
  * Initialize all structure fields to zero, allocate a page from the heap, and
  * zero the bytes that the buffer headers will consume.
  *
  * Return: 0 or -ENOMEM
  */
-int tpm_buf_init(struct tpm_buf *buf)
+int tpm_buf_init(struct tpm_buf *buf, bool alloc, bool sized)
 {
-	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
-	if (!buf->data)
-		return -ENOMEM;
+	if (alloc) {
+		buf->data = (u8 *)__get_free_page(GFP_KERNEL);
+		if (!buf->data)
+			return -ENOMEM;
+	}
+
+	if (sized) {
+		buf->flags = TPM_BUF_SIZED;
+		buf->length = 2;
+	} else {
+		buf->flags = 0;
+		buf->length = TPM_HEADER_SIZE;
+	}
 
-	buf->flags = 0;
-	buf->length = TPM_HEADER_SIZE;
 	memset(buf->data, 0, TPM_HEADER_SIZE);
 
 	return 0;
@@ -73,8 +83,6 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
 
 void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 {
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-
 	/* Return silently if overflow has already happened. */
 	if (buf->flags & TPM_BUF_OVERFLOW)
 		return;
@@ -87,7 +95,11 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
 
 	memcpy(&buf->data[buf->length], new_data, new_length);
 	buf->length += new_length;
-	head->length = cpu_to_be32(buf->length);
+
+	if (buf->flags & TPM_BUF_SIZED)
+		((__be16 *)buf->data)[0] = cpu_to_be16(buf->length - 2);
+	else
+		((struct tpm_header *)buf->data)->length = cpu_to_be32(buf->length);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append);
 
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 557e7f86d98d..047a7064039e 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -44,7 +44,7 @@ static ssize_t pubek_show(struct device *dev, struct device_attribute *attr,
 	if (tpm_try_get_ops(chip))
 		return 0;
 
-	if (tpm_buf_init(&tpm_buf))
+	if (tpm_buf_init(&tpm_buf, true, false))
 		goto out_ops;
 
 	tpm_buf_reset(&tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK);
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index 28fea4e2daaf..396694018590 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -328,7 +328,7 @@ static int tpm1_startup(struct tpm_chip *chip)
 
 	dev_info(&chip->dev, "starting up the TPM manually\n");
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc < 0)
 		return rc;
 
@@ -467,7 +467,7 @@ int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -487,7 +487,7 @@ ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -541,7 +541,7 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	u32 recd;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -592,7 +592,7 @@ int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -629,7 +629,7 @@ static int tpm1_continue_selftest(struct tpm_chip *chip)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -761,7 +761,7 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
 		rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, dummy_hash,
 				     "extending dummy pcr before suspend");
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 94dacbf74e0d..1d3e0833641d 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -183,7 +183,7 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 		expected_digest_size = chip->allocated_banks[i].digest_size;
 	}
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -242,7 +242,7 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	int rc;
 	int i;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -302,7 +302,7 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 	if (!num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	err = tpm_buf_init(&buf);
+	err = tpm_buf_init(&buf, true, false);
 	if (err)
 		return err;
 
@@ -353,7 +353,7 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc) {
 		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
 			 handle);
@@ -394,7 +394,7 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -437,7 +437,7 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return;
 
@@ -467,7 +467,7 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
 	int rc;
 
 	for (full = 0; full < 2; full++) {
-		rc = tpm_buf_init(&buf);
+		rc = tpm_buf_init(&buf, true, false);
 		if (rc)
 			return rc;
 
@@ -504,7 +504,7 @@ int tpm2_probe(struct tpm_chip *chip)
 	struct tpm_buf buf;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -571,7 +571,7 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
 	int rc;
 	int i = 0;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -661,7 +661,7 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
 		goto out;
 	}
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		goto out;
 
@@ -724,7 +724,7 @@ static int tpm2_startup(struct tpm_chip *chip)
 
 	dev_info(&chip->dev, "starting up the TPM manually\n");
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc < 0)
 		return rc;
 
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 43584b4176d6..ab2a863baffb 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -76,7 +76,7 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
 	unsigned int body_size;
 	int rc;
 
-	rc = tpm_buf_init(&tbuf);
+	rc = tpm_buf_init(&tbuf, true, false);
 	if (rc)
 		return rc;
 
@@ -128,7 +128,7 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
 	unsigned int body_size;
 	int rc;
 
-	rc = tpm_buf_init(&tbuf);
+	rc = tpm_buf_init(&tbuf, true, false);
 	if (rc)
 		return rc;
 
diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
index b2b9a15a4a59..52325abd395d 100644
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
@@ -399,7 +399,7 @@ static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
 	const struct tpm_header *header;
 	struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index c355597351c6..687b5173bdab 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -304,6 +304,7 @@ struct tpm_header {
 
 enum tpm_buf_flags {
 	TPM_BUF_OVERFLOW	= BIT(0),
+	TPM_BUF_SIZED		= BIT(1),
 };
 
 struct tpm_buf {
@@ -328,7 +329,7 @@ struct tpm2_hash {
 };
 
 
-int tpm_buf_init(struct tpm_buf *buf);
+int tpm_buf_init(struct tpm_buf *buf, bool alloc, bool sized);
 void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
 void tpm_buf_destroy(struct tpm_buf *buf);
 u32 tpm_buf_length(struct tpm_buf *buf);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
index fcf0eef79ba0..ed5dc3b45d52 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -664,7 +664,7 @@ static int key_seal(struct trusted_key_payload *p,
 	struct tpm_buf tb;
 	int ret;
 
-	ret = tpm_buf_init(&tb);
+	ret = tpm_buf_init(&tb, true, false);
 	if (ret)
 		return ret;
 
@@ -690,7 +690,7 @@ static int key_unseal(struct trusted_key_payload *p,
 	struct tpm_buf tb;
 	int ret;
 
-	ret = tpm_buf_init(&tb);
+	ret = tpm_buf_init(&tb, true, false);
 	if (ret)
 		return ret;
 
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index c54659d06dcb..c41f30770138 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -252,7 +252,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		return rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc) {
 		tpm_put_ops(chip);
 		return rc;
@@ -410,7 +410,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
 	if (blob_len > payload->blob_len)
 		return -E2BIG;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
@@ -467,7 +467,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u8 *data;
 	int rc;
 
-	rc = tpm_buf_init(&buf);
+	rc = tpm_buf_init(&buf, true, false);
 	if (rc)
 		return rc;
 
-- 
2.42.0

Re: [PATCH v3 4/6] tpm: Support TPM2 sized buffers (TPM2B)

[Jarkko Sakkinen]

On Fri, 2023-10-27 at 08:32 -0400, James Bottomley wrote:
> On Tue, 2023-10-24 at 04:15 +0300, Jarkko Sakkinen wrote:
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -7,22 +7,32 @@
> >  #include <linux/tpm.h>
> >  
> >  /**
> > - * tpm_buf_init() - Initialize from the heap
> > + * tpm_buf_init() - Initialize a TPM buffer
> >   * @buf:       A @tpm_buf
> > + * @sized:     Represent a sized buffer (TPM2B)
> > + * @alloc:     Allocate from the heap
> >   *
> >   * Initialize all structure fields to zero, allocate a page from the
> > heap, and
> >   * zero the bytes that the buffer headers will consume.
> >   *
> >   * Return: 0 or -ENOMEM
> >   */
> > -int tpm_buf_init(struct tpm_buf *buf)
> > +int tpm_buf_init(struct tpm_buf *buf, bool alloc, bool sized)
> 
> I think it creates a phenomenally confusing interface to use multiple
> booleans because, unlike flags, it's not self describing at point of
> use.  The confusion is enormously heightened here by having the doc
> book arguments be the reverse of the actual function prototype (I just
> tripped over this).
> 
> The alloc flag is particularly counter intuitive: if you pass in an
> allocated buffer, you expect to be responsible for freeing it again,
> but that's not how you use it; you really use it like a reset not an
> alloc, which looks odd because you already created a separate
> tpm_buf_reset function which can't be used in this case.
> 
> Why not replace the alloc flags with two reset functions: one for TPM2B
> buffers and one for command buffers?
> 
> James

Or you can make that as internal (__tpm_buf_init()) and add two
wrappers.

BR, Jarkko

Re: [PATCH v3 4/6] tpm: Support TPM2 sized buffers (TPM2B)

[Jerry Snitselaar]

On Tue, Oct 24, 2023 at 04:15:22AM +0300, Jarkko Sakkinen wrote:
> Add boolean parameters @alloc and @sized to tpm_buf_init():
> 
> * If @alloc is set to false, buf->data is assumed to be pre-feeded and
>   owned by the caller.
> * If @sized is set to true, the buffer represents a sized buffer
>   (TPM2B).
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
>  drivers/char/tpm/tpm-buf.c                | 32 ++++++++++++++++-------
>  drivers/char/tpm/tpm-sysfs.c              |  2 +-
>  drivers/char/tpm/tpm1-cmd.c               | 14 +++++-----
>  drivers/char/tpm/tpm2-cmd.c               | 22 ++++++++--------
>  drivers/char/tpm/tpm2-space.c             |  4 +--
>  drivers/char/tpm/tpm_vtpm_proxy.c         |  2 +-
>  include/linux/tpm.h                       |  3 ++-
>  security/keys/trusted-keys/trusted_tpm1.c |  4 +--
>  security/keys/trusted-keys/trusted_tpm2.c |  6 ++---
>  9 files changed, 51 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index fa9a4c51157a..f1d92d7e758d 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,22 +7,32 @@
>  #include <linux/tpm.h>
>  
>  /**
> - * tpm_buf_init() - Initialize from the heap
> + * tpm_buf_init() - Initialize a TPM buffer
>   * @buf:	A @tpm_buf
> + * @sized:	Represent a sized buffer (TPM2B)
> + * @alloc:	Allocate from the heap
>   *
>   * Initialize all structure fields to zero, allocate a page from the heap, and

Depending on what the decision ends up being on the bools, flags,
separate functions, or wrappers possibly an "if needed" should be
tacked on to the end of "allocate a page from the heap" here.


Flags would be better when coming across calls to the routine in the
code than the bools, but I think switching to wrappers around
a __tpm_buf_init for the different types would be good.


>   * zero the bytes that the buffer headers will consume.
>   *

Re: [PATCH v3 4/6] tpm: Support TPM2 sized buffers (TPM2B)

[Jarkko Sakkinen]

On Tue Nov 7, 2023 at 7:20 PM EET, Jerry Snitselaar wrote:
> On Tue, Oct 24, 2023 at 04:15:22AM +0300, Jarkko Sakkinen wrote:
> > Add boolean parameters @alloc and @sized to tpm_buf_init():
> > 
> > * If @alloc is set to false, buf->data is assumed to be pre-feeded and
> >   owned by the caller.
> > * If @sized is set to true, the buffer represents a sized buffer
> >   (TPM2B).
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> >  drivers/char/tpm/tpm-buf.c                | 32 ++++++++++++++++-------
> >  drivers/char/tpm/tpm-sysfs.c              |  2 +-
> >  drivers/char/tpm/tpm1-cmd.c               | 14 +++++-----
> >  drivers/char/tpm/tpm2-cmd.c               | 22 ++++++++--------
> >  drivers/char/tpm/tpm2-space.c             |  4 +--
> >  drivers/char/tpm/tpm_vtpm_proxy.c         |  2 +-
> >  include/linux/tpm.h                       |  3 ++-
> >  security/keys/trusted-keys/trusted_tpm1.c |  4 +--
> >  security/keys/trusted-keys/trusted_tpm2.c |  6 ++---
> >  9 files changed, 51 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> > index fa9a4c51157a..f1d92d7e758d 100644
> > --- a/drivers/char/tpm/tpm-buf.c
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -7,22 +7,32 @@
> >  #include <linux/tpm.h>
> >  
> >  /**
> > - * tpm_buf_init() - Initialize from the heap
> > + * tpm_buf_init() - Initialize a TPM buffer
> >   * @buf:	A @tpm_buf
> > + * @sized:	Represent a sized buffer (TPM2B)
> > + * @alloc:	Allocate from the heap
> >   *
> >   * Initialize all structure fields to zero, allocate a page from the heap, and
>
> Depending on what the decision ends up being on the bools, flags,
> separate functions, or wrappers possibly an "if needed" should be
> tacked on to the end of "allocate a page from the heap" here.
>
>
> Flags would be better when coming across calls to the routine in the
> code than the bools, but I think switching to wrappers around
> a __tpm_buf_init for the different types would be good.

Yeah, I'll bake something based on this discussion.

BR, Jarkko

[PATCH v3 5/6] tpm: Add tpm_buf_read_{u8,u16,u32}

[Jarkko Sakkinen]

Add tpm_buf_read_u8(), tpm_buf_read_u16() and tpm_read_u32() for the sake
of more convenient parsing of TPM responses.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm-buf.c | 69 ++++++++++++++++++++++++++++++++++++++
 include/linux/tpm.h        |  3 ++
 2 files changed, 72 insertions(+)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index f1d92d7e758d..bcd3cbcd9dd9 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -124,3 +124,72 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
 	tpm_buf_append(buf, (u8 *)&value2, 4);
 }
 EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
+
+/**
+ * tpm_buf_read() - Read from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ * @count:	the number of bytes to read
+ * @output:	the output buffer
+ */
+static void tpm_buf_read(const struct tpm_buf *buf, off_t *offset, size_t count, void *output)
+{
+	if (*(offset + count) >= buf->length) {
+		WARN(1, "tpm_buf: overflow\n");
+		return;
+	}
+
+	memcpy(output, &buf->data[*offset], count);
+	*offset += count;
+}
+
+/**
+ * tpm_buf_read_u8() - Read 8-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 8-bit word
+ */
+u8 tpm_buf_read_u8(const struct tpm_buf *buf, off_t *offset)
+{
+	u8 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return value;
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u8);
+
+/**
+ * tpm_buf_read_u16() - Read 16-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 16-bit word
+ */
+u16 tpm_buf_read_u16(const struct tpm_buf *buf, off_t *offset)
+{
+	u16 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be16_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u16);
+
+/**
+ * tpm_buf_read_u32() - Read 32-bit word from a TPM buffer
+ * @buf:	&tpm_buf instance
+ * @offset:	offset within the buffer
+ *
+ * Return: next 32-bit word
+ */
+u32 tpm_buf_read_u32(const struct tpm_buf *buf, off_t *offset)
+{
+	u32 value;
+
+	tpm_buf_read(buf, offset, sizeof(value), &value);
+
+	return be32_to_cpu(value);
+}
+EXPORT_SYMBOL_GPL(tpm_buf_read_u32);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 687b5173bdab..6590bd1f0a0e 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -337,6 +337,9 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
 void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
 void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
 void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
+u8 tpm_buf_read_u8(const struct tpm_buf *buf, off_t *offset);
+u16 tpm_buf_read_u16(const struct tpm_buf *buf, off_t *offset);
+u32 tpm_buf_read_u32(const struct tpm_buf *buf, off_t *offset);
 
 /*
  * Check if TPM device is in the firmware upgrade mode.
-- 
2.42.0

Re: [PATCH v3 5/6] tpm: Add tpm_buf_read_{u8,u16,u32}

[Mario Limonciello]

On 10/23/2023 20:15, Jarkko Sakkinen wrote:
> Add tpm_buf_read_u8(), tpm_buf_read_u16() and tpm_read_u32() for the sake
> of more convenient parsing of TPM responses.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
>   drivers/char/tpm/tpm-buf.c | 69 ++++++++++++++++++++++++++++++++++++++
>   include/linux/tpm.h        |  3 ++
>   2 files changed, 72 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index f1d92d7e758d..bcd3cbcd9dd9 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -124,3 +124,72 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
>   	tpm_buf_append(buf, (u8 *)&value2, 4);
>   }
>   EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
> +
> +/**
> + * tpm_buf_read() - Read from a TPM buffer
> + * @buf:	&tpm_buf instance
> + * @offset:	offset within the buffer
> + * @count:	the number of bytes to read
> + * @output:	the output buffer
> + */
> +static void tpm_buf_read(const struct tpm_buf *buf, off_t *offset, size_t count, void *output)
> +{
> +	if (*(offset + count) >= buf->length) {
> +		WARN(1, "tpm_buf: overflow\n");
> +		return;
> +	}

In the overflow case wouldn't you want to pass an error code up instead 
of just showing a WARN trace?

The helper functions can't tell the difference, and the net outcome is 
going to be that if there is overflow you get a warning trace in the 
kernel log and whatever garbage "value" happened to have going to the 
caller.  It's a programmer error but it's also unpredictable what 
happens here.

I think it's cleaner to have callers of 
tpm_buf_read_u8/tpm_buf_read_u16/tpm_buf_read_u32 to to be able to know 
something wrong happened.

> +
> +	memcpy(output, &buf->data[*offset], count);
> +	*offset += count;
> +}
> +
> +/**
> + * tpm_buf_read_u8() - Read 8-bit word from a TPM buffer
> + * @buf:	&tpm_buf instance
> + * @offset:	offset within the buffer
> + *
> + * Return: next 8-bit word
> + */
> +u8 tpm_buf_read_u8(const struct tpm_buf *buf, off_t *offset)
> +{
> +	u8 value;
> +
> +	tpm_buf_read(buf, offset, sizeof(value), &value);
> +
> +	return value;
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_read_u8);
> +
> +/**
> + * tpm_buf_read_u16() - Read 16-bit word from a TPM buffer
> + * @buf:	&tpm_buf instance
> + * @offset:	offset within the buffer
> + *
> + * Return: next 16-bit word
> + */
> +u16 tpm_buf_read_u16(const struct tpm_buf *buf, off_t *offset)
> +{
> +	u16 value;
> +
> +	tpm_buf_read(buf, offset, sizeof(value), &value);
> +
> +	return be16_to_cpu(value);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_read_u16);
> +
> +/**
> + * tpm_buf_read_u32() - Read 32-bit word from a TPM buffer
> + * @buf:	&tpm_buf instance
> + * @offset:	offset within the buffer
> + *
> + * Return: next 32-bit word
> + */
> +u32 tpm_buf_read_u32(const struct tpm_buf *buf, off_t *offset)
> +{
> +	u32 value;
> +
> +	tpm_buf_read(buf, offset, sizeof(value), &value);
> +
> +	return be32_to_cpu(value);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_read_u32);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 687b5173bdab..6590bd1f0a0e 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -337,6 +337,9 @@ void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
>   void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
>   void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
>   void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
> +u8 tpm_buf_read_u8(const struct tpm_buf *buf, off_t *offset);
> +u16 tpm_buf_read_u16(const struct tpm_buf *buf, off_t *offset);
> +u32 tpm_buf_read_u32(const struct tpm_buf *buf, off_t *offset);
>   
>   /*
>    * Check if TPM device is in the firmware upgrade mode.

Re: [PATCH v3 5/6] tpm: Add tpm_buf_read_{u8,u16,u32}

[Jarkko Sakkinen]

On Tue Oct 24, 2023 at 4:38 AM EEST, Mario Limonciello wrote:
> On 10/23/2023 20:15, Jarkko Sakkinen wrote:
> > Add tpm_buf_read_u8(), tpm_buf_read_u16() and tpm_read_u32() for the sake
> > of more convenient parsing of TPM responses.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> >   drivers/char/tpm/tpm-buf.c | 69 ++++++++++++++++++++++++++++++++++++++
> >   include/linux/tpm.h        |  3 ++
> >   2 files changed, 72 insertions(+)
> > 
> > diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> > index f1d92d7e758d..bcd3cbcd9dd9 100644
> > --- a/drivers/char/tpm/tpm-buf.c
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -124,3 +124,72 @@ void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
> >   	tpm_buf_append(buf, (u8 *)&value2, 4);
> >   }
> >   EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
> > +
> > +/**
> > + * tpm_buf_read() - Read from a TPM buffer
> > + * @buf:	&tpm_buf instance
> > + * @offset:	offset within the buffer
> > + * @count:	the number of bytes to read
> > + * @output:	the output buffer
> > + */
> > +static void tpm_buf_read(const struct tpm_buf *buf, off_t *offset, size_t count, void *output)
> > +{
> > +	if (*(offset + count) >= buf->length) {
> > +		WARN(1, "tpm_buf: overflow\n");
> > +		return;
> > +	}
>
> In the overflow case wouldn't you want to pass an error code up instead 
> of just showing a WARN trace?
>
> The helper functions can't tell the difference, and the net outcome is 
> going to be that if there is overflow you get a warning trace in the 
> kernel log and whatever garbage "value" happened to have going to the 
> caller.  It's a programmer error but it's also unpredictable what 
> happens here.
>
> I think it's cleaner to have callers of 
> tpm_buf_read_u8/tpm_buf_read_u16/tpm_buf_read_u32 to to be able to know 
> something wrong happened.

I think you have a fair point here and I also think it is also a bigger
issue for the response parsing than programmer error. I.e. faulty or
malicious TPM could return corrupted data, which makes WARN() wrong
choice.

So, as a corrective measure I think it should be pr_warn() instead, and
instead of returning u8/u16/u32, all functions should return 'ssize_t'
and -EIO in the case of overflow.

Thank you, it was a really good catch.

BR, Jarkko

Re: [PATCH v3 5/6] tpm: Add tpm_buf_read_{u8,u16,u32}

[James Bottomley]

On Tue, 2023-10-24 at 04:15 +0300, Jarkko Sakkinen wrote:
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -124,3 +124,72 @@ void tpm_buf_append_u32(struct tpm_buf *buf,
> const u32 value)
>         tpm_buf_append(buf, (u8 *)&value2, 4);
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
> +
> +/**
> + * tpm_buf_read() - Read from a TPM buffer
> + * @buf:       &tpm_buf instance
> + * @offset:    offset within the buffer
> + * @count:     the number of bytes to read
> + * @output:    the output buffer
> + */
> +static void tpm_buf_read(const struct tpm_buf *buf, off_t *offset,
> size_t count, void *output)
> +{
> +       if (*(offset + count) >= buf->length) {

I don't think you mean that; it's dereferencing a random location in
the stack, which is why I see this check trip randomly when testing.  I
think you mean

if (*offset + count >= buf->length) {

James

Re: [PATCH v3 5/6] tpm: Add tpm_buf_read_{u8,u16,u32}

[Jarkko Sakkinen]

On Fri, 2023-10-27 at 08:24 -0400, James Bottomley wrote:
> On Tue, 2023-10-24 at 04:15 +0300, Jarkko Sakkinen wrote:
> > +++ b/drivers/char/tpm/tpm-buf.c
> > @@ -124,3 +124,72 @@ void tpm_buf_append_u32(struct tpm_buf *buf,
> > const u32 value)
> >         tpm_buf_append(buf, (u8 *)&value2, 4);
> >  }
> >  EXPORT_SYMBOL_GPL(tpm_buf_append_u32);
> > +
> > +/**
> > + * tpm_buf_read() - Read from a TPM buffer
> > + * @buf:       &tpm_buf instance
> > + * @offset:    offset within the buffer
> > + * @count:     the number of bytes to read
> > + * @output:    the output buffer
> > + */
> > +static void tpm_buf_read(const struct tpm_buf *buf, off_t *offset,
> > size_t count, void *output)
> > +{
> > +       if (*(offset + count) >= buf->length) {
> 
> I don't think you mean that; it's dereferencing a random location in
> the stack, which is why I see this check trip randomly when testing.  I
> think you mean
> 
> if (*offset + count >= buf->length) {
> 
> James

Yes, true! Thank you.

BR, Jarkko

[PATCH v3 6/6] KEYS: trusted: tpm2: Use struct tpm_buf for sized buffers

[Jarkko Sakkinen]

Take advantage of the new sized buffer (TPM2B) mode of struct tpm_buf in
tpm2_seal_trusted(). This allows to add robustness to the command
construction without requiring to calculate buffer sizes manually.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v2:
* Use tpm_buf_read_*
---
 security/keys/trusted-keys/trusted_tpm2.c | 51 +++++++++++++----------
 1 file changed, 29 insertions(+), 22 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
index c41f30770138..5d262306184c 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -228,8 +228,9 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_payload *payload,
 		      struct trusted_key_options *options)
 {
+	off_t offset = TPM_HEADER_SIZE;
+	struct tpm_buf buf, sized;
 	int blob_len = 0;
-	struct tpm_buf buf;
 	u32 hash;
 	u32 flags;
 	int i;
@@ -258,6 +259,13 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		return rc;
 	}
 
+	rc = tpm_buf_init(&sized, true, true);
+	if (rc) {
+		tpm_buf_destroy(&buf);
+		tpm_put_ops(chip);
+		return rc;
+	}
+
 	tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
 	tpm_buf_append_u32(&buf, options->keyhandle);
 	tpm2_buf_append_auth(&buf, TPM2_RS_PW,
@@ -267,36 +275,36 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 			     TPM_DIGEST_SIZE);
 
 	/* sensitive */
-	tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len);
+	tpm_buf_append_u16(&sized, options->blobauth_len);
 
-	tpm_buf_append_u16(&buf, options->blobauth_len);
 	if (options->blobauth_len)
-		tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
+		tpm_buf_append(&sized, options->blobauth, options->blobauth_len);
 
-	tpm_buf_append_u16(&buf, payload->key_len);
-	tpm_buf_append(&buf, payload->key, payload->key_len);
+	tpm_buf_append_u16(&sized, payload->key_len);
+	tpm_buf_append(&sized, payload->key, payload->key_len);
+	tpm_buf_append(&buf, sized.data, sized.length);
 
 	/* public */
-	tpm_buf_append_u16(&buf, 14 + options->policydigest_len);
-	tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH);
-	tpm_buf_append_u16(&buf, hash);
+	tpm_buf_init(&sized, false, true);
+	tpm_buf_append_u16(&sized, TPM_ALG_KEYEDHASH);
+	tpm_buf_append_u16(&sized, hash);
 
 	/* key properties */
 	flags = 0;
 	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
-	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM |
-					    TPM2_OA_FIXED_PARENT);
-	tpm_buf_append_u32(&buf, flags);
+	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT);
+	tpm_buf_append_u32(&sized, flags);
 
 	/* policy */
-	tpm_buf_append_u16(&buf, options->policydigest_len);
+	tpm_buf_append_u16(&sized, options->policydigest_len);
 	if (options->policydigest_len)
-		tpm_buf_append(&buf, options->policydigest,
-			       options->policydigest_len);
+		tpm_buf_append(&sized, options->policydigest, options->policydigest_len);
 
 	/* public parameters */
-	tpm_buf_append_u16(&buf, TPM_ALG_NULL);
-	tpm_buf_append_u16(&buf, 0);
+	tpm_buf_append_u16(&sized, TPM_ALG_NULL);
+	tpm_buf_append_u16(&sized, 0);
+
+	tpm_buf_append(&buf, sized.data, sized.length);
 
 	/* outside info */
 	tpm_buf_append_u16(&buf, 0);
@@ -313,21 +321,20 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 	if (rc)
 		goto out;
 
-	blob_len = be32_to_cpup((__be32 *) &buf.data[TPM_HEADER_SIZE]);
+	blob_len = tpm_buf_read_u32(&buf, &offset);
 	if (blob_len > MAX_BLOB_SIZE) {
 		rc = -E2BIG;
 		goto out;
 	}
-	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
+	if (buf.length - offset < blob_len) {
 		rc = -EFAULT;
 		goto out;
 	}
 
-	blob_len = tpm2_key_encode(payload, options,
-				   &buf.data[TPM_HEADER_SIZE + 4],
-				   blob_len);
+	blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len);
 
 out:
+	tpm_buf_destroy(&sized);
 	tpm_buf_destroy(&buf);
 
 	if (rc > 0) {
-- 
2.42.0