When running memory balloon tests on Elm I can frequently see this crash:

<1>[ 8638.396764] Unable to handle kernel NULL pointer dereference at virtual address 0000007c
<1>[ 8638.396782] pgd = ffffffc0dcf2c000
<1>[ 8638.396787] [0000007c] *pgd=0000000130e65003, *pud=0000000130e65003, *pmd=00000001343d8003, *pte=0000000000000000
<0>[ 8638.396804] Internal error: Oops: 96000007 [#1] PREEMPT SMP
<4>[ 8638.396810] Modules linked in: uinput rfcomm cmac uvcvideo videobuf2_vmalloc btmrvl_sdio btmrvl i2c_dev ipt_MASQUERADE nf_nat_masquerade_ipv4 bl
uetooth iptable_nat nf_nat_ipv4 nf_nat xt_mark bridge stp llc fuse zram ip6table_filter snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq snd_seq_de
vice mwifiex_sdio mwifiex asix usbnet mii cfg80211 joydev
<4>[ 8638.396896] CPU: 0 PID: 4730 Comm: balloon.arm Not tainted 3.18.0 #10
<4>[ 8638.396901] Hardware name: Mediatek Elm rev2, rev1 board (DT)
<4>[ 8638.396906] task: ffffffc0a7a93100 ti: ffffffc077614000 task.ti: ffffffc077614000
<4>[ 8638.396919] PC is at skb_put+0x20/0xac
<4>[ 8638.396929] LR is at asix_rx_fixup_internal+0x16c/0x1f8 [asix]
<4>[ 8638.396934] pc : [<ffffffc0007c4848>] lr : [<ffffffbffc098bdc>] pstate: 80000145


There's a fix upstream:
f6194bcf net: usb: asix: Fix crash on skb alloc failure