net: bcmgenet: fix NULL dereference in set_coalesce before first open

Overview

In the Linux kernel, the following vulnerability has been resolved:

net: bcmgenet: fix NULL dereference in set_coalesce before first open

The Rx ring priv and index are only set in bcmgenet_init_rx_ring(), which runs at open. Setting the Rx coalescing parameters on an interface that was never opened, e.g. "ethtool -C eth0 rx-usecs 50", dereferences a NULL ring->priv. The oops happens with RTNL held, so networking stays stuck until a reboot:

Unable to handle kernel paging request at virtual address 0000000000002788 pc : bcmgenet_set_rx_coalesce.isra.0+0x10/0x88 lr : bcmgenet_set_coalesce+0xe8/0x180 Call trace: bcmgenet_set_rx_coalesce.isra.0+0x10/0x88 (P) __ethnl_set_coalesce.isra.0+0x490/0x570 ethnl_set_coalesce+0x48/0xc0 ethnl_default_set_doit+0xf4/0x230 genl_family_rcv_msg_doit+0xe8/0x160 genl_rcv_msg+0x220/0x2a0 netlink_rcv_skb+0x68/0x140 genl_rcv+0x40/0x60 netlink_unicast+0x338/0x3c0 netlink_sendmsg+0x19c/0x3f8 __sock_sendmsg+0x64/0xc0 __sys_sendto+0x124/0x198 __arm64_sys_sendto+0x30/0x48

Set priv and index at probe. Writing the registers while the interface is down is harmless because open resets the MAC and bcmgenet_init_rx_coalesce() reapplies the stored values.

It was observed on a Raspberry Pi CM4, but should apply to all other genet devices.

Affected

• Linux >= 9f4ca05827a27ec73bf63a42732f1978b8a779af < 0d867b91598b6ed2f75998c34f4e2869631da31e
• Linux >= 9f4ca05827a27ec73bf63a42732f1978b8a779af < 2294b62eaec6fd3c76a261d287f66641eeafd5f0
• Linux >= 9f4ca05827a27ec73bf63a42732f1978b8a779af < d870102b5425390cab42eebbf3d19ec6a43c6734
• Linux >= 9f4ca05827a27ec73bf63a42732f1978b8a779af < 19419faf58dfe5bcc8a9e60e622976c5f8e3ddc1
• Linux 4.17

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.