From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934655AbdKGAkr (ORCPT ); Mon, 6 Nov 2017 19:40:47 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:53991 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933294AbdKGA2F (ORCPT ); Mon, 6 Nov 2017 19:28:05 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Dan Priamo" , "Stephen Douthit" , "Neil Horman" , "Wolfram Sang" Date: Mon, 06 Nov 2017 23:03:02 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 167/294] i2c: ismt: Don't duplicate the receive length for block reads In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 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 3.16.50-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Stephen Douthit commit b6c159a9cb69c2cf0bf59d4e12c3a2da77e4d994 upstream. According to Table 15-14 of the C2000 EDS (Intel doc #510524) the rx data pointed to by the descriptor dptr contains the byte count. desc->rxbytes reports all bytes read on the wire, including the "byte count" byte. So if a device sends 4 bytes in response to a block read, on the wire and in the DMA buffer we see: count data1 data2 data3 data4 0x04 0xde 0xad 0xbe 0xef That's what we want to return in data->block to the next level. Instead we were actually prefixing that with desc->rxbytes: bad count count data1 data2 data3 data4 0x05 0x04 0xde 0xad 0xbe 0xef This was discovered while developing a BMC solution relying on the ipmi_ssif.c driver which was trying to interpret the bogus length field as part of the IPMI response. Signed-off-by: Stephen Douthit Tested-by: Dan Priamo Acked-by: Neil Horman Signed-off-by: Wolfram Sang Signed-off-by: Ben Hutchings --- drivers/i2c/busses/i2c-ismt.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/i2c/busses/i2c-ismt.c +++ b/drivers/i2c/busses/i2c-ismt.c @@ -344,8 +344,8 @@ static int ismt_process_desc(const struc break; case I2C_SMBUS_BLOCK_DATA: case I2C_SMBUS_I2C_BLOCK_DATA: - memcpy(&data->block[1], dma_buffer, desc->rxbytes); - data->block[0] = desc->rxbytes; + memcpy(data->block, dma_buffer, desc->rxbytes); + data->block[0] = desc->rxbytes - 1; break; } return 0;