tpm: fix sleep-in-spinlock

flush_scheduled_work() can sleep, and we're calling it under spinlock.

AFAICS, moving flush_scheduled_work before spin_lock() should not cause any
problems.

Reason being - The only thing that can race against tpm_release is tpm_open
(tpm_release is called when last reference to the file is closed and only
thing that can happen after that is tpm_open??) and tpm_open acquires
driver_lock and more over it bails out with EBUSY if chip->num_opens is
greater than 0.

I also moved chip->num_pending-- to after deleting timer and setting data
pending as it looks more correct for the paranoid although it probably doesn't
matter as it is guarded by driver_lock.  None the less this change should not
cause problems.

While I was at it I noticed a missing NULL check in tpm_register_hardware
which is fixed with this patch as well.

Signed-off-by: Parag Warudkar <parag.warudkar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
index e5a254a434f8..ef991cd8c024 100644
--- a/drivers/char/tpm/tpm.c
+++ b/drivers/char/tpm/tpm.c
@@ -942,12 +942,12 @@ int tpm_release(struct inode *inode, struct file *file)
 {
         struct tpm_chip *chip = file->private_data;
 
+        flush_scheduled_work();
         spin_lock(&driver_lock);
         file->private_data = NULL;
-        chip->num_opens--;
         del_singleshot_timer_sync(&chip->user_read_timer);
-        flush_scheduled_work();
         atomic_set(&chip->data_pending, 0);
+        chip->num_opens--;
         put_device(chip->dev);
         kfree(chip->data_buffer);
         spin_unlock(&driver_lock);
@@ -1097,8 +1097,13 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
 
         /* Driver specific per-device data */
         chip = kzalloc(sizeof(*chip), GFP_KERNEL);
-        if (chip == NULL)
+        devname = kmalloc(DEVNAME_SIZE, GFP_KERNEL);
+
+        if (chip == NULL || devname == NULL) {
+                kfree(chip);
+                kfree(devname);
                 return NULL;
+        }
 
         init_MUTEX(&chip->buffer_mutex);
         init_MUTEX(&chip->tpm_mutex);
@@ -1124,7 +1129,6 @@ struct tpm_chip *tpm_register_hardware(struct device *dev, const struct tpm_vend
 
         set_bit(chip->dev_num, dev_mask);
 
-        devname = kmalloc(DEVNAME_SIZE, GFP_KERNEL);
         scnprintf(devname, DEVNAME_SIZE, "%s%d", "tpm", chip->dev_num);
         chip->vendor.miscdev.name = devname;