Re: warn in ncsi netlink code

Sam Mendoza-Jonas
2022-11-20T00:27:42Z

On November 17, 2022 3:35:17 PM GMT+11:00, Joel Stanley <joel@jms.id.au> wrote:
>next-20221114 running on an ast2600 system produced this:
>
>[ 44.627332] ------------[ cut here ]------------
>[ 44.632657] WARNING: CPU: 0 PID: 508 at net/ncsi/ncsi-cmd.c:231
>ncsi_cmd_handler_oem+0xbc/0xd0
>[ 44.642387] memcpy: detected field-spanning write (size 7) of
>single field "&cmd->mfr_id" at net/ncsi/ncsi-cmd.c:231 (size 4)
>[ 44.655131] CPU: 0 PID: 508 Comm: ncsi-netlink Not tainted
>6.1.0-rc5-14066-gefbdad8553d8 #17
>[ 44.664577] Hardware name: Generic DT based system
>[ 44.664599] unwind_backtrace from show_stack+0x18/0x1c
>[ 44.675801] show_stack from dump_stack_lvl+0x40/0x4c
>[ 44.681458] dump_stack_lvl from __warn+0xb8/0x12c
>[ 44.686814] __warn from warn_slowpath_fmt+0x9c/0xd8
>[ 44.692370] warn_slowpath_fmt from ncsi_cmd_handler_oem+0xbc/0xd0
>[ 44.699285] ncsi_cmd_handler_oem from ncsi_xmit_cmd+0x160/0x29c
>[ 44.706002] ncsi_xmit_cmd from ncsi_send_cmd_nl+0x13c/0x1dc
>[ 44.712337] ncsi_send_cmd_nl from genl_rcv_msg+0x1d0/0x440
>[ 44.718579] genl_rcv_msg from netlink_rcv_skb+0xc0/0x120
>[ 44.724623] netlink_rcv_skb from genl_rcv+0x28/0x3c
>[ 44.730182] genl_rcv from netlink_unicast+0x208/0x370
>[ 44.735934] netlink_unicast from netlink_sendmsg+0x1e4/0x450
>[ 44.742365] netlink_sendmsg from ____sys_sendmsg+0x23c/0x2b8
>[ 44.748799] ____sys_sendmsg from ___sys_sendmsg+0x9c/0xd0
>[ 44.754941] ___sys_sendmsg from sys_sendmsg+0x78/0xbc
>[ 44.760695] sys_sendmsg from ret_fast_syscall+0x0/0x54
>[ 44.766544] Exception stack(0xb57b1fa8 to 0xb57b1ff0)
>[ 44.772191] 1fa0: 0244f330 0244f1e0 00000003
>7ee36a60 00000000 00000000
>[ 44.781328] 1fc0: 0244f330 0244f1e0 76f35c60 00000128 76f91550
>0244f387 0244f387 00498e7c
>[ 44.790462] 1fe0: 76f35d34 7ee36a10 76f1b510 76bba140
>[ 44.796186] ---[ end trace 0000000000000000 ]---
>
>The relevant code:
>
>static int ncsi_cmd_handler_oem(struct sk_buff *skb,
> struct ncsi_cmd_arg *nca)
>{
> struct ncsi_cmd_oem_pkt *cmd;
> unsigned int len;
> int payload;
> /* NC-SI spec DSP_0222_1.2.0, section 8.2.2.2
> * requires payload to be padded with 0 to
> * 32-bit boundary before the checksum field.
> * Ensure the padding bytes are accounted for in
> * skb allocation
> */
>
> payload = ALIGN(nca->payload, 4);
> len = sizeof(struct ncsi_cmd_pkt_hdr) + 4;
> len += max(payload, padding_bytes);
>
> cmd = skb_put_zero(skb, len);
> memcpy(&cmd->mfr_id, nca->data, nca->payload);
> ncsi_cmd_build_header(&cmd->cmd.common, nca);
>
> return 0;
>}
>
>I think it's copying the command payload to the command packet,
>starting at the offset of mfr_id:
>
>struct ncsi_cmd_oem_pkt {
> struct ncsi_cmd_pkt_hdr cmd; /* Command header */
> __be32 mfr_id; /* Manufacture ID */
> unsigned char data[]; /* OEM Payload Data */
>};
>
>But I'm not too sure.
>
>Cheers,
>
>Joel

While it looks a little gross I'm pretty sure this is the intended behavior for the OEM commands. We'll need to massage that into something nicer.

Thanks!
Sam