The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3ab2011ea368ec3433ad49e1b9e1c7b70d2e65df Mon Sep 17 00:00:00 2001

From: Tadeusz Struk tadeusz.struk@intel.com Date: Tue, 22 May 2018 14:37:18 -0700 Subject: [PATCH] tpm: fix race condition in tpm_common_write()

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

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c index 230b99288024..e4a04b2d3c32 100644 --- a/drivers/char/tpm/tpm-dev-common.c +++ b/drivers/char/tpm/tpm-dev-common.c @@ -37,7 +37,7 @@ 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); } @@ -46,7 +46,6 @@ void tpm_common_open(struct file *file, struct tpm_chip *chip, struct file_priv *priv) { priv->chip = chip; - atomic_set(&priv->data_pending, 0); mutex_init(&priv->buffer_mutex); timer_setup(&priv->user_read_timer, user_reader_timeout, 0); INIT_WORK(&priv->work, timeout_work); @@ -58,29 +57,24 @@ ssize_t tpm_common_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 orig_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 */ - 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; }

@@ -91,17 +85,19 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, size_t in_size = size; ssize_t out_size;

+ 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 (atomic_read(&priv->data_pending) != 0) + if (priv->data_pending != 0) { + mutex_unlock(&priv->buffer_mutex); return -EBUSY; - - if (in_size > TPM_BUFSIZE) - return -E2BIG; - - mutex_lock(&priv->buffer_mutex); + }

if (copy_from_user (priv->data_buffer, (void __user *) buf, in_size)) { @@ -132,7 +128,7 @@ ssize_t tpm_common_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 */ @@ -149,5 +145,5 @@ void tpm_common_release(struct file *file, struct file_priv *priv) 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; } diff --git a/drivers/char/tpm/tpm-dev.h b/drivers/char/tpm/tpm-dev.h index ba3b6f9dacf7..b24cfb4d3ee1 100644 --- a/drivers/char/tpm/tpm-dev.h +++ b/drivers/char/tpm/tpm-dev.h @@ -8,7 +8,7 @@ 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 */