From: Rajiv A. <sr...@li...> - 2011-12-20 16:38:33
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On 06/12/11 16:29, Tim Gardner wrote: > 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<set...@ca...> > Cc: Debora Velarde<de...@li...> > Cc: Rajiv Andrade<sr...@li...> > Cc: Marcel Selhorst<m.s...@si...> > Cc: tpm...@li... > Cc: st...@vg... > Signed-off-by: Tim Gardner<tim...@ca...> > --- > 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; What about just moving atomic_set(&chip->data_pending, 0); to here? If I'm not missing anything, this would be cleaner. Rajiv > - > - mutex_unlock(&chip->buffer_mutex); > } > > + mutex_unlock(&chip->buffer_mutex); > return ret_size; > } > EXPORT_SYMBOL_GPL(tpm_read); |