[PATCH] usb: musb: Check requset->buf before use to avoid crash issue

[Xingxing Luo]

When connecting USB to PC, there is a very low probability of kernel
crash. The reason is that in ep0_txstate(), the buf member of struct
usb_request used may be a null pointer. Therefore, it needs to
determine whether it is null before using it.

[ 4888.071462][T597@C0] Call trace:
[ 4888.071467][T597@C0]  musb_default_write_fifo+0xa0/0x1ac [musb_hdrc]
[ 4888.087190][T597@C0]  musb_write_fifo+0x3c/0x90 [musb_hdrc]
[ 4888.099826][T597@C0]  ep0_txstate+0x78/0x218 [musb_hdrc]
[ 4888.153918][T597@C0]  musb_g_ep0_irq+0x3c4/0xe10 [musb_hdrc]
[ 4888.159663][T597@C0]  musb_interrupt+0xab4/0xf1c [musb_hdrc]
[ 4888.165391][T597@C0]  sprd_musb_interrupt+0x1e4/0x484 [musb_sprd]
[ 4888.171447][T597@C0]  __handle_irq_event_percpu+0xd8/0x2f8
[ 4888.176901][T597@C0]  handle_irq_event+0x70/0xe4
[ 4888.181487][T597@C0]  handle_fasteoi_irq+0x15c/0x230
[ 4888.186420][T597@C0]  handle_domain_irq+0x88/0xfc
[ 4888.191090][T597@C0]  gic_handle_irq+0x60/0x138
[ 4888.195591][T597@C0]  call_on_irq_stack+0x40/0x70
[ 4888.200263][T597@C0]  do_interrupt_handler+0x50/0xac
[ 4888.205196][T597@C0]  el1_interrupt+0x34/0x64
[ 4888.209524][T597@C0]  el1h_64_irq_handler+0x1c/0x2c
[ 4888.214370][T597@C0]  el1h_64_irq+0x7c/0x80
[ 4888.218525][T597@C0]  __check_heap_object+0x1ac/0x1fc
[ 4888.223544][T597@C0]  __check_object_size+0x10c/0x20c
[ 4888.228563][T597@C0]  simple_copy_to_iter+0x40/0x74
[ 4888.233410][T597@C0]  __skb_datagram_iter+0xa0/0x310
[ 4888.238343][T597@C0]  skb_copy_datagram_iter+0x44/0x110
[ 4888.243535][T597@C0]  netlink_recvmsg+0xdc/0x364
[ 4888.248123][T597@C0]  ____sys_recvmsg.llvm.16749613423860851707+0x358/0x6c0
[ 4888.255045][T597@C0]  ___sys_recvmsg+0xe0/0x1dc
[ 4888.259544][T597@C0]  __arm64_sys_recvmsg+0xc4/0x10c
[ 4888.264478][T597@C0]  invoke_syscall+0x6c/0x15c
[ 4888.268976][T597@C0]  el0_svc_common.llvm.12373701176611417606+0xd4/0x120
[ 4888.275726][T597@C0]  do_el0_svc+0x34/0xac
[ 4888.279795][T597@C0]  el0_svc+0x28/0x90
[ 4888.283603][T597@C0]  el0t_64_sync_handler+0x88/0xec
[ 4888.288548][T597@C0]  el0t_64_sync+0x1b4/0x1b8
[ 4888.292956][T597@C0] Code: 540002c3 53027ea8 aa1303e9 71000508 (b840452a)
[ 4888.299789][T597@C0] ---[ end trace 14a301b7253e83cc ]---

Signed-off-by: Xingxing Luo <xingxing.luo@xxxxxxxxxx>
---
 drivers/usb/musb/musb_gadget_ep0.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/musb/musb_gadget_ep0.c b/drivers/usb/musb/musb_gadget_ep0.c
index 6d7336727388..5d0629866128 100644
--- a/drivers/usb/musb/musb_gadget_ep0.c
+++ b/drivers/usb/musb/musb_gadget_ep0.c
@@ -531,6 +531,11 @@ static void ep0_txstate(struct musb *musb)
 
 	request = &req->request;
 
+	if (!requset->buf) {
+		musb_dbg(musb, "request->buf is NULL");
+		return;
+	}
+
 	/* load the data */
 	fifo_src = (u8 *) request->buf + request->actual;
 	fifo_count = min((unsigned) MUSB_EP0_FIFOSIZE,
-- 
2.17.1