==================================================================
BUG: KASAN: use-after-free in u_audio_iso_complete+0x24c/0x520 [u_audio]
Read of size 8 at addr ffff8006cafcc248 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        WC      4.14.47+ #160
Hardware name: Renesas Salvator-X board based on r8a7795 ES2.0+ (DT)
Call trace:
[<ffff2000080925ac>] dump_backtrace+0x0/0x364
[<ffff200008092924>] show_stack+0x14/0x1c
[<ffff200008f8dbcc>] dump_stack+0x108/0x174
[<ffff2000083c71b8>] print_address_description+0x7c/0x32c
[<ffff2000083c78e8>] kasan_report+0x324/0x354
[<ffff2000083c6114>] __asan_load8+0x24/0x94
[<ffff2000021d1b34>] u_audio_iso_complete+0x24c/0x520 [u_audio]
[<ffff20000152fe50>] usb_gadget_giveback_request+0x480/0x4d0 [udc_core]
[<ffff200001860ab8>] usbhsg_queue_done+0x100/0x130 [renesas_usbhs]
[<ffff20000185f814>] usbhsf_pkt_handler+0x1a4/0x298 [renesas_usbhs]
[<ffff20000185fb38>] usbhsf_irq_ready+0x128/0x178 [renesas_usbhs]
[<ffff200001859cc8>] usbhs_interrupt+0x440/0x490 [renesas_usbhs]
[<ffff2000081a0288>] __handle_irq_event_percpu+0x594/0xa58
[<ffff2000081a07d0>] handle_irq_event_percpu+0x84/0x12c
[<ffff2000081a0928>] handle_irq_event+0xb0/0x10c
[<ffff2000081a8384>] handle_fasteoi_irq+0x1e0/0x2ec
[<ffff20000819e5f8>] generic_handle_irq+0x2c/0x44
[<ffff20000819f0d0>] __handle_domain_irq+0x190/0x194
[<ffff20000808177c>] gic_handle_irq+0x80/0xac
Exception stack(0xffff200009e97c80 to 0xffff200009e97dc0)
7c80: 0000000000000000 0000000000000000 0000000000000003 ffff200008179298
7ca0: ffff20000ae1c180 dfff200000000000 0000000000000000 ffff2000081f9a88
7cc0: ffff200009eb5960 ffff200009e97cf0 0000000000001600 ffff0400041b064b
7ce0: 0000000000000000 0000000000000002 0000000200000001 0000000000000001
7d00: ffff20000842197c 0000ffff958c4970 0000000000000000 ffff8006da0d5b80
7d20: ffff8006d4678498 0000000000000000 000000126bde0a8b ffff8006d4678480
7d40: 0000000000000000 000000126bdbea64 ffff200008fd0000 ffff8006fffff980
7d60: 00000000495f0018 ffff200009e97dc0 ffff200008b6c4ec ffff200009e97dc0
7d80: ffff200008b6c4f0 0000000020000145 ffff8006da0d5b80 ffff8006d4678498
7da0: ffffffffffffffff ffff8006d4678498 ffff200009e97dc0 ffff200008b6c4f0
[<ffff200008084034>] el1_irq+0xb4/0x12c
[<ffff200008b6c4f0>] cpuidle_enter_state+0x818/0x844
[<ffff200008b6c59c>] cpuidle_enter+0x18/0x20
[<ffff20000815f2e4>] call_cpuidle+0x98/0x9c
[<ffff20000815f674>] do_idle+0x214/0x264
[<ffff20000815facc>] cpu_startup_entry+0x20/0x24
[<ffff200008fb09d8>] rest_init+0x30c/0x320
[<ffff2000095f1338>] start_kernel+0x570/0x5b0
---<-snip->---

Fixes: 132fcb460839 ("usb: gadget: Add Audio Class 2.0 Driver")
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
---
 drivers/usb/gadget/function/u_audio.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index 8a63009b7cd5..fb5ed97572e5 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -79,7 +79,7 @@ static const struct snd_pcm_hardware uac_pcm_hardware = {
 static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
 {
 	unsigned pending;
-	unsigned long flags;
+	unsigned long flags, flags2;
 	unsigned int hw_ptr;
 	int status = req->status;
 	struct uac_req *ur = req->context;
@@ -106,7 +106,14 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
 	if (!substream)
 		goto exit;
 
+	snd_pcm_stream_lock_irqsave(substream, flags2);
+
 	runtime = substream->runtime;
+	if (!runtime || !snd_pcm_running(substream)) {
+		snd_pcm_stream_unlock_irqrestore(substream, flags2);
+		goto exit;
+	}
+
 	spin_lock_irqsave(&prm->lock, flags);
 
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
@@ -165,6 +172,7 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
 	prm->hw_ptr = (hw_ptr + req->actual) % runtime->dma_bytes;
 	hw_ptr = prm->hw_ptr;
 	spin_unlock_irqrestore(&prm->lock, flags);
+	snd_pcm_stream_unlock_irqrestore(substream, flags2);
 
 	if ((hw_ptr % snd_pcm_lib_period_bytes(substream)) < req->actual)
 		snd_pcm_period_elapsed(substream);
