Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756610Ab2J1X13 (ORCPT ); Sun, 28 Oct 2012 19:27:29 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41880 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756419Ab2J1X1W (ORCPT ); Sun, 28 Oct 2012 19:27:22 -0400 Message-Id: <20121028231608.402217142@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 28 Oct 2012 23:17:17 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Peter Huewe , Kent Yoder , Greg Kroah-Hartman Subject: [ 101/105] tpm: Propagate error from tpm_transmit to fix a timeout hang In-Reply-To: <20121028231536.970033833@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3649 Lines: 101 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Huewe commit abce9ac292e13da367bbd22c1f7669f988d931ac upstream. tpm_write calls tpm_transmit without checking the return value and assigns the return value unconditionally to chip->pending_data, even if it's an error value. This causes three bugs. So if we write to /dev/tpm0 with a tpm_param_size bigger than TPM_BUFSIZE=0x1000 (e.g. 0x100a) and a bufsize also bigger than TPM_BUFSIZE (e.g. 0x100a) tpm_transmit returns -E2BIG which is assigned to chip->pending_data as -7, but tpm_write returns that TPM_BUFSIZE bytes have been successfully been written to the TPM, altough this is not true (bug #1). As we did write more than than TPM_BUFSIZE bytes but tpm_write reports that only TPM_BUFSIZE bytes have been written the vfs tries to write the remaining bytes (in this case 10 bytes) to the tpm device driver via tpm_write which then blocks at /* 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) msleep(TPM_TIMEOUT); for 60 seconds, since data_pending is -7 and nobody is able to read it (since tpm_read luckily checks if data_pending is greater than 0) (#bug 2). After that the remaining bytes are written to the TPM which are interpreted by the tpm as a normal command. (bug #3) So if the last bytes of the command stream happen to be a e.g. tpm_force_clear this gets accidentally sent to the TPM. This patch fixes all three bugs, by propagating the error code of tpm_write and returning -E2BIG if the input buffer is too big, since the response from the tpm for a truncated value is bogus anyway. Moreover it returns -EBUSY to userspace if there is a response ready to be read. Signed-off-by: Peter Huewe Signed-off-by: Kent Yoder Signed-off-by: Greg Kroah-Hartman Signed-off-by: Ben Hutchings --- drivers/char/tpm/tpm.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) --- a/drivers/char/tpm/tpm.c +++ b/drivers/char/tpm/tpm.c @@ -1186,17 +1186,20 @@ ssize_t tpm_write(struct file *file, con size_t size, loff_t *off) { struct tpm_chip *chip = file->private_data; - size_t in_size = size, out_size; + 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 */ - while (atomic_read(&chip->data_pending) != 0) - msleep(TPM_TIMEOUT); - - mutex_lock(&chip->buffer_mutex); + either via tpm_read or a user_read_timer timeout. + This also prevents splitted buffered writes from blocking here. + */ + if (atomic_read(&chip->data_pending) != 0) + return -EBUSY; if (in_size > TPM_BUFSIZE) - in_size = TPM_BUFSIZE; + return -E2BIG; + + mutex_lock(&chip->buffer_mutex); if (copy_from_user (chip->data_buffer, (void __user *) buf, in_size)) { @@ -1206,6 +1209,10 @@ ssize_t tpm_write(struct file *file, con /* atomic tpm command send and result receive */ out_size = tpm_transmit(chip, chip->data_buffer, TPM_BUFSIZE); + if (out_size < 0) { + mutex_unlock(&chip->buffer_mutex); + return out_size; + } atomic_set(&chip->data_pending, out_size); mutex_unlock(&chip->buffer_mutex); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/