[PATCH] tpm: Define TPM2_SPACE_BUFFER_SIZE to replace the use of PAGE_SIZE

[Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>]

The size of the buffers for storing context's and sessions can vary from
arch to arch as PAGE_SIZE can be anything between 4 kB and 256 kB (the
maximum for PPC64). Define a fixed buffer size set to 16 kB. This should
be enough for most use with three handles (that is how many we allow at
the moment).

Reported-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 745b361e989a ("tpm: infrastructure for TPM spaces")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 drivers/char/tpm/tpm2-space.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 982d341d8837..9bef646093d1 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -15,6 +15,8 @@
 #include <asm/unaligned.h>
 #include "tpm.h"
 
+#define TPM2_SPACE_BUFFER_SIZE		16384 /* 16 kB */
+
 enum tpm2_handle_types {
 	TPM2_HT_HMAC_SESSION	= 0x02000000,
 	TPM2_HT_POLICY_SESSION	= 0x03000000,
@@ -40,11 +42,11 @@ static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
 
 int tpm2_init_space(struct tpm_space *space)
 {
-	space->context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	space->context_buf = kzalloc(TPM2_SPACE_BUFFER_SIZE, GFP_KERNEL);
 	if (!space->context_buf)
 		return -ENOMEM;
 
-	space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	space->session_buf = kzalloc(TPM2_SPACE_BUFFER_SIZE, GFP_KERNEL);
 	if (space->session_buf == NULL) {
 		kfree(space->context_buf);
 		return -ENOMEM;
@@ -311,8 +313,10 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
 	       sizeof(space->context_tbl));
 	memcpy(&chip->work_space.session_tbl, &space->session_tbl,
 	       sizeof(space->session_tbl));
-	memcpy(chip->work_space.context_buf, space->context_buf, PAGE_SIZE);
-	memcpy(chip->work_space.session_buf, space->session_buf, PAGE_SIZE);
+	memcpy(chip->work_space.context_buf, space->context_buf,
+	       TPM2_SPACE_BUFFER_SIZE);
+	memcpy(chip->work_space.session_buf, space->session_buf,
+	       TPM2_SPACE_BUFFER_SIZE);
 
 	rc = tpm2_load_space(chip);
 	if (rc) {
@@ -492,8 +496,8 @@ static int tpm2_save_space(struct tpm_chip *chip)
 			continue;
 
 		rc = tpm2_save_context(chip, space->context_tbl[i],
-				       space->context_buf, PAGE_SIZE,
-				       &offset);
+				       space->context_buf,
+				       TPM2_SPACE_BUFFER_SIZE, &offset);
 		if (rc == -ENOENT) {
 			space->context_tbl[i] = 0;
 			continue;
@@ -509,9 +513,8 @@ static int tpm2_save_space(struct tpm_chip *chip)
 			continue;
 
 		rc = tpm2_save_context(chip, space->session_tbl[i],
-				       space->session_buf, PAGE_SIZE,
-				       &offset);
-
+				       space->session_buf,
+				       TPM2_SPACE_BUFFER_SIZE, &offset);
 		if (rc == -ENOENT) {
 			/* handle error saving session, just forget it */
 			space->session_tbl[i] = 0;
@@ -557,8 +560,10 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
 	       sizeof(space->context_tbl));
 	memcpy(&space->session_tbl, &chip->work_space.session_tbl,
 	       sizeof(space->session_tbl));
-	memcpy(space->context_buf, chip->work_space.context_buf, PAGE_SIZE);
-	memcpy(space->session_buf, chip->work_space.session_buf, PAGE_SIZE);
+	memcpy(space->context_buf, chip->work_space.context_buf,
+	       TPM2_SPACE_BUFFER_SIZE);
+	memcpy(space->session_buf, chip->work_space.session_buf,
+	       TPM2_SPACE_BUFFER_SIZE);
 
 	return 0;
 out:
-- 
2.25.1