Re: [PATCH v2] tpm: tpm2-space: Resize session and context buffers dynamically

[Stefan Berger]

On 6/25/20 12:38 AM, Jarkko Sakkinen wrote:
Re-allocate context and session buffers when needed. Scale them in page
increments so that the reallocation is only seldomly required, and thus
causes minimal stress to the system. Add a static maximum limit of four
pages for buffer sizes.
Cc: James Bottomley <james.bottom...@hansenpartnership.com>
Suggested-by: Stefan Berger <stef...@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
---
Tested only for compilation.
v2: TPM2_SPACE_DEFAULT_BUFFER_SIZE
  drivers/char/tpm/tpm2-space.c | 87 ++++++++++++++++++++++++-----------
  include/linux/tpm.h           |  6 ++-
  2 files changed, 64 insertions(+), 29 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 982d341d8837..b8ece01d6afb 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -15,6 +15,9 @@
  #include <asm/unaligned.h>
  #include "tpm.h"
  
+#define TPM2_SPACE_DEFAULT_BUFFER_SIZE	PAGE_SIZE
+#define TPM2_SPACE_MAX_BUFFER_SIZE     (4 * PAGE_SIZE)
+
  enum tpm2_handle_types {
        TPM2_HT_HMAC_SESSION    = 0x02000000,
        TPM2_HT_POLICY_SESSION  = 0x03000000,
@@ -557,8 +588,10 @@ 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,
+              space->context_size);


You have to allocate the max size the in tpm_chip_alloc (tpm-chip.c):

   chip->work_space.context_buf = kzalloc(TPM2_SPACE_MAX_BUFFER_SIZE, 
GFP_KERNEL);


+       memcpy(space->session_buf, chip->work_space.session_buf,
+              space->session_size);
  


same for this


        return 0;
  out:
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 03e9b184411b..9ea39e8f7162 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -92,10 +92,12 @@ enum tpm_duration {
  #define TPM_PPI_VERSION_LEN           3
  
  struct tpm_space {
+       u8  *context_buf;
+       u8  *session_buf;
+       u32 context_size;
+       u32 session_size;
        u32 context_tbl[3];
-       u8 *context_buf;
        u32 session_tbl[3];
-       u8 *session_buf;
  };
  
  struct tpm_bios_log {