From: Tadeusz Struk tadeusz.struk@intel.com

commit 3ab2011ea368ec3433ad49e1b9e1c7b70d2e65df upstream

There is a race condition in tpm_common_write function allowing two threads on the same /dev/tpm<N>, or two different applications on the same /dev/tpmrm<N> to overwrite each other commands/responses. Fixed this by taking the priv->buffer_mutex early in the function.

Also converted the priv->data_pending from atomic to a regular size_t type. There is no need for it to be atomic since it is only touched under the protection of the priv->buffer_mutex.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Tadeusz Struk tadeusz.struk@intel.com Reviewed-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Signed-off-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com --- Manually backported for v4.4 and v4.9. drivers/char/tpm/tpm-dev.c | 43 ++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/drivers/char/tpm/tpm-dev.c b/drivers/char/tpm/tpm-dev.c index 65b824954bdc..1662e4688ee2 100644 --- a/drivers/char/tpm/tpm-dev.c +++ b/drivers/char/tpm/tpm-dev.c @@ -25,7 +25,7 @@ struct file_priv { struct tpm_chip *chip;

/* Data passed to and from the tpm via the read/write calls */ - atomic_t data_pending; + size_t data_pending; struct mutex buffer_mutex;

struct timer_list user_read_timer; /* user needs to claim result */ @@ -46,7 +46,7 @@ static void timeout_work(struct work_struct *work) struct file_priv *priv = container_of(work, struct file_priv, work);

mutex_lock(&priv->buffer_mutex); - atomic_set(&priv->data_pending, 0); + priv->data_pending = 0; memset(priv->data_buffer, 0, sizeof(priv->data_buffer)); mutex_unlock(&priv->buffer_mutex); } @@ -72,7 +72,6 @@ static int tpm_open(struct inode *inode, struct file *file) }

priv->chip = chip; - atomic_set(&priv->data_pending, 0); mutex_init(&priv->buffer_mutex); setup_timer(&priv->user_read_timer, user_reader_timeout, (unsigned long)priv); @@ -86,28 +85,24 @@ static ssize_t tpm_read(struct file *file, char __user *buf, size_t size, loff_t *off) { struct file_priv *priv = file->private_data; - ssize_t ret_size; + ssize_t ret_size = 0; int rc;

del_singleshot_timer_sync(&priv->user_read_timer); flush_work(&priv->work); - ret_size = atomic_read(&priv->data_pending); - if (ret_size > 0) { /* relay data */ - ssize_t orig_ret_size = ret_size; - if (size < ret_size) - ret_size = size; + mutex_lock(&priv->buffer_mutex);

- mutex_lock(&priv->buffer_mutex); + if (priv->data_pending) { + ret_size = min_t(ssize_t, size, priv->data_pending); rc = copy_to_user(buf, priv->data_buffer, ret_size); - memset(priv->data_buffer, 0, orig_ret_size); + memset(priv->data_buffer, 0, priv->data_pending); if (rc) ret_size = -EFAULT;

- mutex_unlock(&priv->buffer_mutex); + priv->data_pending = 0; }

- atomic_set(&priv->data_pending, 0); - + mutex_unlock(&priv->buffer_mutex); return ret_size; }

@@ -118,18 +113,20 @@ static ssize_t tpm_write(struct file *file, const char __user *buf, size_t in_size = size; ssize_t out_size;

- /* cannot perform a write until the read has cleared - either via tpm_read or a user_read_timer timeout. - This also prevents splitted buffered writes from blocking here. - */ - if (atomic_read(&priv->data_pending) != 0) - return -EBUSY; - if (in_size > TPM_BUFSIZE) return -E2BIG;

mutex_lock(&priv->buffer_mutex);

+ /* Cannot perform a write until the read has cleared either via + * tpm_read or a user_read_timer timeout. This also prevents split + * buffered writes from blocking here. + */ + if (priv->data_pending != 0) { + mutex_unlock(&priv->buffer_mutex); + return -EBUSY; + } + if (copy_from_user (priv->data_buffer, (void __user *) buf, in_size)) { mutex_unlock(&priv->buffer_mutex); @@ -159,7 +156,7 @@ static ssize_t tpm_write(struct file *file, const char __user *buf, return out_size; }

- atomic_set(&priv->data_pending, out_size); + priv->data_pending = out_size; mutex_unlock(&priv->buffer_mutex);

/* Set a timeout by which the reader must come claim the result */ @@ -178,7 +175,7 @@ static int tpm_release(struct inode *inode, struct file *file) del_singleshot_timer_sync(&priv->user_read_timer); flush_work(&priv->work); file->private_data = NULL; - atomic_set(&priv->data_pending, 0); + priv->data_pending = 0; clear_bit(0, &priv->chip->is_open); kfree(priv); return 0;