lkml.org 
[lkml]   [2019]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.0 108/115] tpm: fix an invalid condition in tpm_common_poll
    Date
    [ Upstream commit 7110629263469b4664d00b38ef80a656eddf3637 ]

    The poll condition should only check response_length,
    because reads should only be issued if there is data to read.
    The response_read flag only prevents double writes.
    The problem was that the write set the response_read to false,
    enqued a tpm job, and returned. Then application called poll
    which checked the response_read flag and returned EPOLLIN.
    Then the application called read, but got nothing.
    After all that the async_work kicked in.
    Added also mutex_lock around the poll check to prevent
    other possible race conditions.

    Fixes: 9488585b21bef0df12 ("tpm: add support for partial reads")
    Reported-by: Mantas Mikulėnas <grawity@gmail.com>
    Tested-by: Mantas Mikulėnas <grawity@gmail.com>
    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>
    Signed-off-by: James Morris <james.morris@microsoft.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/char/tpm/tpm-dev-common.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
    index 5eecad233ea1..744b0237300a 100644
    --- a/drivers/char/tpm/tpm-dev-common.c
    +++ b/drivers/char/tpm/tpm-dev-common.c
    @@ -203,12 +203,19 @@ __poll_t tpm_common_poll(struct file *file, poll_table *wait)
    __poll_t mask = 0;

    poll_wait(file, &priv->async_wait, wait);
    + mutex_lock(&priv->buffer_mutex);

    - if (!priv->response_read || priv->response_length)
    + /*
    + * The response_length indicates if there is still response
    + * (or part of it) to be consumed. Partial reads decrease it
    + * by the number of bytes read, and write resets it the zero.
    + */
    + if (priv->response_length)
    mask = EPOLLIN | EPOLLRDNORM;
    else
    mask = EPOLLOUT | EPOLLWRNORM;

    + mutex_unlock(&priv->buffer_mutex);
    return mask;
    }

    --
    2.19.1


    \
     
     \ /
      Last update: 2019-04-24 19:39    [W:4.034 / U:0.376 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site