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Subject[PATCH =v2 1/3] tpm: fix invalid locking in NONBLOCKING mode
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Date
When an application sends TPM commands in NONBLOCKING mode
the driver holds chip->tpm_mutex returning from write(),
which triggers: "WARNING: lock held when returning to user space".
To fix this issue the driver needs to release the mutex before
returning and acquire it again in tpm_dev_async_work() before
sending the command.

Cc: stable@vger.kernel.org
Fixes: 9e1b74a63f776 (tpm: add support for nonblocking operation)
Reported-by: Jeffrin Jose T <jeffrin@rajagiritech.edu.in>
Tested-by: Jeffrin Jose T <jeffrin@rajagiritech.edu.in>
Signed-off-by: Tadeusz Struk <tadeusz.struk@intel.com>
---
Changes in v2:
- Updated commit message as requested
- Add the fix and test updates to the same series
---
drivers/char/tpm/tpm-dev-common.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 2ec47a69a2a6..b23b0b999232 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -61,6 +61,12 @@ static void tpm_dev_async_work(struct work_struct *work)

mutex_lock(&priv->buffer_mutex);
priv->command_enqueued = false;
+ ret = tpm_try_get_ops(priv->chip);
+ if (ret) {
+ priv->response_length = ret;
+ goto out;
+ }
+
ret = tpm_dev_transmit(priv->chip, priv->space, priv->data_buffer,
sizeof(priv->data_buffer));
tpm_put_ops(priv->chip);
@@ -68,6 +74,7 @@ static void tpm_dev_async_work(struct work_struct *work)
priv->response_length = ret;
mod_timer(&priv->user_read_timer, jiffies + (120 * HZ));
}
+out:
mutex_unlock(&priv->buffer_mutex);
wake_up_interruptible(&priv->async_wait);
}
@@ -204,6 +211,7 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf,
if (file->f_flags & O_NONBLOCK) {
priv->command_enqueued = true;
queue_work(tpm_dev_wq, &priv->async_work);
+ tpm_put_ops(priv->chip);
mutex_unlock(&priv->buffer_mutex);
return size;
}
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