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[2.42.72.229]) by smtp.gmail.com with ESMTPSA id y9-v6sm613127wru.70.2018.11.07.08.50.57 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Nov 2018 08:50:57 -0800 (PST) From: Paolo Pisati To: Woojung Huh , Microchip Linux Driver Support , netdev@vger.kernel.org, stable@vger.kernel.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] [stable, netdev 4.4+] lan78xx: make sure RX_ADDRL & RX_ADDRH regs are always up to date Date: Wed, 7 Nov 2018 17:50:57 +0100 Message-Id: <1541609457-28725-1-git-send-email-p.pisati@gmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP [partial backport upstream 760db29bdc97b73ff60b091315ad787b1deb5cf5] Upon invocation, lan78xx_init_mac_address() checks that the mac address present in the RX_ADDRL & RX_ADDRH registers is a valid address, if not, it first tries to read a new address from an external eeprom or the otp area, and in case both read fail (or the address read back is invalid), it randomly generates a new one. Unfortunately, due to the way the above logic is laid out, if both read_eeprom() and read_otp() fail, a new mac address is correctly generated but is never written back to RX_ADDRL & RX_ADDRH, leaving the chip in an incosistent state and with an invalid mac address (e.g. the nic appears to be completely dead, and doesn't receive any packet, etc): lan78xx_init_mac_address() ... if (lan78xx_read_eeprom(addr ...) || lan78xx_read_otp(addr ...)) { if (is_valid_ether_addr(addr) { // nop... } else { random_ether_addr(addr); } // correctly writes back the new address lan78xx_write_reg(RX_ADDRL, addr ...); lan78xx_write_reg(RX_ADDRH, addr ...); } else { // XXX if both eeprom and otp read fail, we land here and skip // XXX the RX_ADDRL & RX_ADDRH update completely random_ether_addr(addr); } This bug went unnoticed because lan78xx_read_otp() was buggy itself and would never fail, up until 4bfc338 "lan78xx: Correctly indicate invalid OTP" fixed it and as a side effect uncovered this bug. 4.18+ is fine, since the bug was implicitly fixed in 760db29 "lan78xx: Read MAC address from DT if present" when the address change logic was reorganized, but it's still present in all stable trees below that: linux-4.4.y, linux-4.9.y, linux-4.14.y, etc up to linux-4.18.y (not included). Signed-off-by: Paolo Pisati Tested-by: Paolo Pisati --- drivers/net/usb/lan78xx.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/net/usb/lan78xx.c b/drivers/net/usb/lan78xx.c index 50e2e10a..114dc55 100644 --- a/drivers/net/usb/lan78xx.c +++ b/drivers/net/usb/lan78xx.c @@ -1660,13 +1660,6 @@ static void lan78xx_init_mac_address(struct lan78xx_net *dev) netif_dbg(dev, ifup, dev->net, "MAC address set to random addr"); } - - addr_lo = addr[0] | (addr[1] << 8) | - (addr[2] << 16) | (addr[3] << 24); - addr_hi = addr[4] | (addr[5] << 8); - - ret = lan78xx_write_reg(dev, RX_ADDRL, addr_lo); - ret = lan78xx_write_reg(dev, RX_ADDRH, addr_hi); } else { /* generate random MAC */ random_ether_addr(addr); @@ -1674,6 +1667,11 @@ static void lan78xx_init_mac_address(struct lan78xx_net *dev) "MAC address set to random addr"); } } + addr_lo = addr[0] | (addr[1] << 8) | (addr[2] << 16) | (addr[3] << 24); + addr_hi = addr[4] | (addr[5] << 8); + + ret = lan78xx_write_reg(dev, RX_ADDRL, addr_lo); + ret = lan78xx_write_reg(dev, RX_ADDRH, addr_hi); ret = lan78xx_write_reg(dev, MAF_LO(0), addr_lo); ret = lan78xx_write_reg(dev, MAF_HI(0), addr_hi | MAF_HI_VALID_);