Re: [PATCH net] net: bcmgenet: fix NULL dereference in set_coalesce before first open

On 9/28/26 03:56, Nicolai Buchwitz wrote:

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.

Fixes: 9f4ca05827a2 ("net: bcmgenet: Add support for adaptive RX coalescing")
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>

Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>

Thanks Nicolai!
-- 
Florian