Currently, the event log file operations are not serialized with
tpm_chip_unregister(), which can possibly cause a race condition.

This patch fixes the race condition by:
 - moving read_log() from fops to chip register.
 - disallowing event log file operations when chip unregister is in
   progress.
 - guarding event log memory using chip krefs.

Suggested-by: Jason Gunthorpe <jguntho...@obsidianresearch.com>
Signed-off-by: Nayna Jain <na...@linux.vnet.ibm.com>
---
 drivers/char/tpm/tpm-chip.c     |  1 +
 drivers/char/tpm/tpm.h          | 11 ++++++
 drivers/char/tpm/tpm_acpi.c     | 12 +++++--
 drivers/char/tpm/tpm_eventlog.c | 80 ++++++++++++++++++++++++++---------------
 drivers/char/tpm/tpm_eventlog.h |  2 +-
 drivers/char/tpm/tpm_of.c       |  4 ++-
 6 files changed, 76 insertions(+), 34 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index eac1f10..813e0d7 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -127,6 +127,7 @@ static void tpm_dev_release(struct device *dev)
        idr_remove(&dev_nums_idr, chip->dev_num);
        mutex_unlock(&idr_lock);
 
+       kfree(chip->log.bios_event_log);
        kfree(chip);
 }
 
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 4c118a4..bfe93e6 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -35,6 +35,8 @@
 #include <linux/cdev.h>
 #include <linux/highmem.h>
 
+#include "tpm_eventlog.h"
+
 enum tpm_const {
        TPM_MINOR = 224,        /* officially assigned */
        TPM_BUFSIZE = 4096,
@@ -146,6 +148,11 @@ enum tpm_chip_flags {
        TPM_CHIP_FLAG_VIRTUAL           = BIT(3),
 };
 
+struct tpm_chip_seqops {
+       struct tpm_chip *chip;
+       const struct seq_operations *seqops;
+};
+
 struct tpm_chip {
        struct device dev;
        struct cdev cdev;
@@ -157,6 +164,10 @@ struct tpm_chip {
        struct rw_semaphore ops_sem;
        const struct tpm_class_ops *ops;
 
+       struct tpm_bios_log log;
+       struct tpm_chip_seqops bin_log_seqops;
+       struct tpm_chip_seqops ascii_log_seqops;
+
        unsigned int flags;
 
        int dev_num;            /* /dev/tpm# */
diff --git a/drivers/char/tpm/tpm_acpi.c b/drivers/char/tpm/tpm_acpi.c
index 565a947..4d6c2d7 100644
--- a/drivers/char/tpm/tpm_acpi.c
+++ b/drivers/char/tpm/tpm_acpi.c
@@ -45,13 +45,15 @@ struct acpi_tcpa {
 };
 
 /* read binary bios log */
-int read_log(struct tpm_bios_log *log)
+int read_log(struct tpm_chip *chip)
 {
        struct acpi_tcpa *buff;
        acpi_status status;
        void __iomem *virt;
        u64 len, start;
+       struct tpm_bios_log *log;
 
+       log = &chip->log;
        if (log->bios_event_log != NULL) {
                printk(KERN_ERR
                       "%s: ERROR - Eventlog already initialized\n",
@@ -97,13 +99,17 @@ int read_log(struct tpm_bios_log *log)
 
        virt = acpi_os_map_iomem(start, len);
        if (!virt) {
-               kfree(log->bios_event_log);
                printk("%s: ERROR - Unable to map memory\n", __func__);
-               return -EIO;
+               goto err;
        }
 
        memcpy_fromio(log->bios_event_log, virt, len);
 
        acpi_os_unmap_iomem(virt, len);
        return 0;
+
+err:
+       kfree(log->bios_event_log);
+       return -EIO;
+
 }
diff --git a/drivers/char/tpm/tpm_eventlog.c b/drivers/char/tpm/tpm_eventlog.c
index 753e92d..bb142f2 100644
--- a/drivers/char/tpm/tpm_eventlog.c
+++ b/drivers/char/tpm/tpm_eventlog.c
@@ -73,7 +73,8 @@ static const char* tcpa_pc_event_id_strings[] = {
 static void *tpm_bios_measurements_start(struct seq_file *m, loff_t *pos)
 {
        loff_t i;
-       struct tpm_bios_log *log = m->private;
+       struct tpm_chip *chip = m->private;
+       struct tpm_bios_log *log = &chip->log;
        void *addr = log->bios_event_log;
        void *limit = log->bios_event_log_end;
        struct tcpa_event *event;
@@ -120,7 +121,8 @@ static void *tpm_bios_measurements_next(struct seq_file *m, 
void *v,
                                        loff_t *pos)
 {
        struct tcpa_event *event = v;
-       struct tpm_bios_log *log = m->private;
+       struct tpm_chip *chip = m->private;
+       struct tpm_bios_log *log = &chip->log;
        void *limit = log->bios_event_log_end;
        u32 converted_event_size;
        u32 converted_event_type;
@@ -261,13 +263,10 @@ static int tpm_binary_bios_measurements_show(struct 
seq_file *m, void *v)
 static int tpm_bios_measurements_release(struct inode *inode,
                                         struct file *file)
 {
-       struct seq_file *seq = file->private_data;
-       struct tpm_bios_log *log = seq->private;
+       struct seq_file *seq = (struct seq_file *)file->private_data;
+       struct tpm_chip *chip = (struct tpm_chip *)seq->private;
 
-       if (log) {
-               kfree(log->bios_event_log);
-               kfree(log);
-       }
+       put_device(&chip->dev);
 
        return seq_release(inode, file);
 }
@@ -323,36 +322,34 @@ static int tpm_bios_measurements_open(struct inode *inode,
                                            struct file *file)
 {
        int err;
-       struct tpm_bios_log *log;
        struct seq_file *seq;
-       const struct seq_operations *seqops =
-               (const struct seq_operations *)inode->i_private;
-
-       log = kzalloc(sizeof(struct tpm_bios_log), GFP_KERNEL);
-       if (!log)
-               return -ENOMEM;
-
-       if ((err = read_log(log)))
-               goto out_free;
+       struct tpm_chip_seqops *chip_seqops;
+       const struct seq_operations *seqops;
+       struct tpm_chip *chip;
+
+       inode_lock(inode);
+       if (!inode->i_private) {
+               inode_unlock(inode);
+               return -ENODEV;
+       }
+       chip_seqops = (struct tpm_chip_seqops *)inode->i_private;
+       seqops = chip_seqops->seqops;
+       chip = chip_seqops->chip;
+       get_device(&chip->dev);
 
        /* now register seq file */
        err = seq_open(file, seqops);
        if (!err) {
                seq = file->private_data;
-               seq->private = log;
-       } else {
-               goto out_free;
+               seq->private = chip;
        }
 
-out:
+       inode_unlock(inode);
        return err;
-out_free:
-       kfree(log->bios_event_log);
-       kfree(log);
-       goto out;
 }
 
 static const struct file_operations tpm_bios_measurements_ops = {
+       .owner = THIS_MODULE,
        .open = tpm_bios_measurements_open,
        .read = seq_read,
        .llseek = seq_lseek,
@@ -372,10 +369,22 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
 {
        const char *name = dev_name(&chip->dev);
        unsigned int cnt;
+       int rc = 0;
 
        if (chip->flags & TPM_CHIP_FLAG_TPM2)
                return 0;
 
+       rc = read_log(chip);
+       /*
+        * read_log failure means event log is not supported except for ENOMEM
+        */
+       if (rc < 0) {
+               if (rc == -ENOMEM)
+                       return rc;
+               else
+                       return 0;
+       }
+
        cnt = 0;
        chip->bios_dir[cnt] =
                securityfs_create_dir(name, NULL);
@@ -383,19 +392,25 @@ int tpm_bios_log_setup(struct tpm_chip *chip)
                goto err;
        cnt++;
 
+       chip->bin_log_seqops.chip = chip;
+       chip->bin_log_seqops.seqops = &tpm_binary_b_measurments_seqops;
+
        chip->bios_dir[cnt] =
            securityfs_create_file("binary_bios_measurements",
                                   S_IRUSR | S_IRGRP, chip->bios_dir[0],
-                                  (void *)&tpm_binary_b_measurments_seqops,
+                                  (void *)&chip->bin_log_seqops,
                                   &tpm_bios_measurements_ops);
        if (is_bad(chip->bios_dir[cnt]))
                goto err;
        cnt++;
 
+       chip->ascii_log_seqops.chip = chip;
+       chip->ascii_log_seqops.seqops = &tpm_ascii_b_measurments_seqops;
+
        chip->bios_dir[cnt] =
            securityfs_create_file("ascii_bios_measurements",
                                   S_IRUSR | S_IRGRP, chip->bios_dir[0],
-                                  (void *)&tpm_ascii_b_measurments_seqops,
+                                  (void *)&chip->ascii_log_seqops,
                                   &tpm_bios_measurements_ops);
        if (is_bad(chip->bios_dir[cnt]))
                goto err;
@@ -412,7 +427,14 @@ err:
 void tpm_bios_log_teardown(struct tpm_chip *chip)
 {
        int i;
+       struct inode *inode;
 
-       for (i = (TPM_NUM_EVENT_LOG_FILES - 1); i >= 0; i--)
+       for (i = (TPM_NUM_EVENT_LOG_FILES - 1); i >= 0; i--) {
+               inode = d_inode(chip->bios_dir[i]);
+               inode_lock(inode);
+               inode->i_private = NULL;
+               inode_unlock(inode);
                securityfs_remove(chip->bios_dir[i]);
+       }
+
 }
diff --git a/drivers/char/tpm/tpm_eventlog.h b/drivers/char/tpm/tpm_eventlog.h
index fd3357e..6df2f8e 100644
--- a/drivers/char/tpm/tpm_eventlog.h
+++ b/drivers/char/tpm/tpm_eventlog.h
@@ -73,7 +73,7 @@ enum tcpa_pc_event_ids {
        HOST_TABLE_OF_DEVICES,
 };
 
-int read_log(struct tpm_bios_log *log);
+int read_log(struct tpm_chip *chip);
 
 #if defined(CONFIG_TCG_IBMVTPM) || defined(CONFIG_TCG_IBMVTPM_MODULE) || \
        defined(CONFIG_ACPI)
diff --git a/drivers/char/tpm/tpm_of.c b/drivers/char/tpm/tpm_of.c
index 570f30c..68d891a 100644
--- a/drivers/char/tpm/tpm_of.c
+++ b/drivers/char/tpm/tpm_of.c
@@ -20,12 +20,14 @@
 #include "tpm.h"
 #include "tpm_eventlog.h"
 
-int read_log(struct tpm_bios_log *log)
+int read_log(struct tpm_chip *chip)
 {
        struct device_node *np;
        const u32 *sizep;
        const u64 *basep;
+       struct tpm_bios_log *log;
 
+       log = &chip->log;
        if (log->bios_event_log != NULL) {
                pr_err("%s: ERROR - Eventlog already initialized\n", __func__);
                return -EFAULT;
-- 
2.5.0


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