tpm: fix compat 'ppi' link handling in tpm_chip_register()

__compat_only_sysfs_link_entry_to_kobj() was unconditionally called for
TPM1 chips, which caused crash on Acer C720 laptop where DSM for the
ACPI object did not exist.

There are two reasons for unwanted behavior:

* The code did not check whether
  __compat_only_sysfs_link_entry_to_kobj() returned -ENOENT. This is
  OK. It just meanst that ppi is not available.
* The code did not clean up properly. Compat link should added only
  after all other init is done.

This patch sorts out these issues.

Fixes: 9b774d5cf2db
Reported-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jeremiah Mahler <jmmahler@gmail.com>
Acked-by: Peter Huewe <PeterHuewe@gmx.de>

1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index a5cdce74adab..45cc39aabeee 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -226,14 +226,6 @@ int tpm_chip_register(struct tpm_chip *chip)
         if (rc)
                 goto out_err;
 
-        if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
-                rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
-                                                            &chip->dev.kobj,
-                                                            "ppi");
-                if (rc)
-                        goto out_err;
-        }
-
         /* Make the chip available. */
         spin_lock(&driver_lock);
         list_add_tail_rcu(&chip->list, &tpm_chip_list);
@@ -241,6 +233,16 @@ int tpm_chip_register(struct tpm_chip *chip)
 
         chip->flags |= TPM_CHIP_FLAG_REGISTERED;
 
+        if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
+                rc = __compat_only_sysfs_link_entry_to_kobj(&chip->pdev->kobj,
+                                                            &chip->dev.kobj,
+                                                            "ppi");
+                if (rc && rc != -ENOENT) {
+                        tpm_chip_unregister(chip);
+                        return rc;
+                }
+        }
+
         return 0;
 out_err:
         tpm1_chip_unregister(chip);