Messages in this thread Patch in this message | | | From | Tim Gardner <> | Subject | [PATCH 2/3] TPM: Close data_pending and data_buffer races | Date | Tue, 6 Dec 2011 11:29:21 -0700 |
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There is a race betwen tpm_read() and tpm_write where both chip->data_pending and chip->data_buffer can be changed by tpm_write() when tpm_read() clears chip->data_pending, but before tpm_read() grabs the mutex.
Protect changes to chip->data_pending and chip->data_buffer by expanding the scope of chip->buffer_mutex.
Reported-by: Seth Forshee <seth.forshee@canonical.com> Cc: Debora Velarde <debora@linux.vnet.ibm.com> Cc: Rajiv Andrade <srajiv@linux.vnet.ibm.com> Cc: Marcel Selhorst <m.selhorst@sirrix.com> Cc: tpmdd-devel@lists.sourceforge.net Cc: stable@vger.kernel.org Signed-off-by: Tim Gardner <tim.gardner@canonical.com> --- drivers/char/tpm/tpm.c | 17 +++++++++-------- 1 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c index b366b34..70bf9e5 100644 --- a/drivers/char/tpm/tpm.c +++ b/drivers/char/tpm/tpm.c @@ -1074,12 +1074,15 @@ ssize_t tpm_write(struct file *file, const char __user *buf, struct tpm_chip *chip = file->private_data; size_t in_size = size, out_size; + mutex_lock(&chip->buffer_mutex); + /* cannot perform a write until the read has cleared either via tpm_read or a user_read_timer timeout */ - while (atomic_read(&chip->data_pending) != 0) + while (atomic_read(&chip->data_pending) != 0) { + mutex_unlock(&chip->buffer_mutex); msleep(TPM_TIMEOUT); - - mutex_lock(&chip->buffer_mutex); + mutex_lock(&chip->buffer_mutex); + } if (in_size > TPM_BUFSIZE) in_size = TPM_BUFSIZE; @@ -1112,22 +1115,20 @@ ssize_t tpm_read(struct file *file, char __user *buf, del_singleshot_timer_sync(&chip->user_read_timer); flush_work_sync(&chip->work); - ret_size = atomic_read(&chip->data_pending); - atomic_set(&chip->data_pending, 0); + mutex_lock(&chip->buffer_mutex); + ret_size = atomic_xchg(&chip->data_pending, 0); if (ret_size > 0) { /* relay data */ ssize_t orig_ret_size = ret_size; if (size < ret_size) ret_size = size; - mutex_lock(&chip->buffer_mutex); rc = copy_to_user(buf, chip->data_buffer, ret_size); memset(chip->data_buffer, 0, orig_ret_size); if (rc) ret_size = -EFAULT; - - mutex_unlock(&chip->buffer_mutex); } + mutex_unlock(&chip->buffer_mutex); return ret_size; } EXPORT_SYMBOL_GPL(tpm_read); -- 1.7.0.4
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