A regression was introduced in commit 9c349892 ("brcmfmac: revise
handling events in receive path") which moves eth_type_trans() call
to brcmf_rx_frame(). Msgbuf layer doesn't use brcmf_rx_frame() but invokes
brcmf_netif_rx() directly. In such case the Ethernet header was not
stripped out resulting in null pointer dereference in the networking
stack.

BUG: unable to handle kernel NULL pointer dereference at 0000000000000048
IP: [<ffffffff814c3ce6>] enqueue_to_backlog+0x56/0x260
PGD 0
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: fuse ipt_MASQUERADE nf_nat_masquerade_ipv4
iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 xt_addrtype
[...]
rtsx_pci scsi_mod usbcore usb_common i8042 serio nvme nvme_core
CPU: 7 PID: 1340 Comm: irq/136-brcmf_p Not tainted 4.7.0-rc1-mainline #1
Hardware name: Dell Inc. XPS 15 9550/0N7TVV, BIOS 01.02.00 04/07/2016
task: ffff8804a0c5bd00 ti: ffff88049e124000 task.ti: ffff88049e124000
RIP: 0010:[<ffffffff814c3ce6>] [<ffffffff814c3ce6>]
enqueue_to_backlog+0x56/0x260
RSP: 0018:ffff88049e127ca0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8804bddd7c40 RCX: 000000000000002f
RDX: 0000000000000000 RSI: 0000000000000007 RDI: ffff8804bddd7d4c
RBP: ffff88049e127ce8 R08: 0000000000000000 R09: 0000000000000000
R10: ffff8804bddd12c0 R11: 000000000000149e R12: 0000000000017c40
R13: ffff88049e127d08 R14: ffff8804a9bd6d00 R15: ffff8804bddd7d4c
FS: 0000000000000000(0000) GS:ffff8804bddc0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000048 CR3: 0000000001806000 CR4: 00000000003406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
ffff8804bdddad00 ffff8804ad089e00 0000000000000000 0000000000000282
0000000000000000 ffff8804a9bd6d00 ffff8804a1b27e00 ffff8804a9bd6d00
ffff88002ee88000 ffff88049e127d28 ffffffff814c3f3b ffffffff81311fc3
Call Trace:
[<ffffffff814c3f3b>] netif_rx_internal+0x4b/0x170
[<ffffffff81311fc3>] ? swiotlb_tbl_unmap_single+0xf3/0x120
[<ffffffff814c5467>] netif_rx_ni+0x27/0xc0
[<ffffffffa08519e9>] brcmf_netif_rx+0x49/0x70 [brcmfmac]
[<ffffffffa08564d4>] brcmf_msgbuf_process_rx+0x2b4/0x570 [brcmfmac]
[<ffffffff81020017>] ? __xen_set_pgd_hyper+0x57/0xd0
[<ffffffff810d60b0>] ? irq_forced_thread_fn+0x70/0x70
[<ffffffffa0857381>] brcmf_proto_msgbuf_rx_trigger+0x31/0xe0 [brcmfmac]
[<ffffffffa0861e8f>] brcmf_pcie_isr_thread+0x7f/0x110 [brcmfmac]
[<ffffffff810d60d0>] irq_thread_fn+0x20/0x50
[<ffffffff810d63ad>] irq_thread+0x12d/0x1c0
[<ffffffff815d07d5>] ? __schedule+0x2f5/0x7a0
[<ffffffff810d61d0>] ? wake_threads_waitq+0x30/0x30
[<ffffffff810d6280>] ? irq_thread_dtor+0xb0/0xb0
[<ffffffff81098ea8>] kthread+0xd8/0xf0
[<ffffffff815d4b7f>] ret_from_fork+0x1f/0x40
[<ffffffff81098dd0>] ? kthread_worker_fn+0x170/0x170
Code: 1c f5 60 9a 8e 81 9c 58 0f 1f 44 00 00 48 89 45 d0 fa 66 0f 1f
44 00 00 4c 8d bb 0c 01 00 00 4c 89 ff e8 5e 08 11 00 49 8b 56 20 <48>
8b 52 48 83 e2 01 74 10 8b 8b 08 01 00 00 8b 15 59 c5 42 00
RIP [<ffffffff814c3ce6>] enqueue_to_backlog+0x56/0x260
RSP <ffff88049e127ca0>
CR2: 0000000000000048

Fixes: 9c349892 ("brcmfmac: revise handling events in receive path")
Reported-by: Rafal Milecki <zajec5@gmail.com>
Reported-by: Grey Christoforo <grey@christoforo.net>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Signed-off-by: Franky Lin <franky.lin@broadcom.com>
[arend@broadcom.com: rephrased the commit message]
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>