Hi Greg,
On 08/26/2018 10:14 AM, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
This is a note to let you know that I've just added the patch titled
usb: gadget: u_audio: protect stream runtime fields with stream spinlock
to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-gadget-u_audio-protect-stream-runtime-fields-with-stream-spinlock.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
From foo@baz Sun Aug 26 09:13:00 CEST 2018
From: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
Date: Thu, 21 Jun 2018 17:22:52 +0200
Subject: usb: gadget: u_audio: protect stream runtime fields with stream spinlock
From: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
[ Upstream commit 56bc61587daadef67712068f251c4ef2e3932d94 ]
The change protects almost the whole body of u_audio_iso_complete()
function by PCM stream lock, this is mainly sufficient to avoid a race
between USB request completion and stream termination, the change
prevents a possibility of invalid memory access in interrupt context
by memcpy():
Unable to handle kernel paging request at virtual address 00004e80
pgd = c0004000
[00004e80] *pgd=00000000
Internal error: Oops: 817 [#1] PREEMPT SMP ARM
CPU: 0 PID: 3 Comm: ksoftirqd/0 Tainted: G C 3.14.54+ #117
task: da180b80 ti: da192000 task.ti: da192000
PC is at memcpy+0x50/0x330
LR is at 0xcdd92b0e
pc : [<c029ef30>] lr : [<cdd92b0e>] psr: 20000193
sp : da193ce4 ip : dd86ae26 fp : 0000b180
r10: daf81680 r9 : 00000000 r8 : d58a01ea
r7 : 2c0b43e4 r6 : acdfb08b r5 : 01a271cf r4 : 87389377
r3 : 69469782 r2 : 00000020 r1 : daf82fe0 r0 : 00004e80
Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: 10c5387d Table: 2b70804a DAC: 00000015
Process ksoftirqd/0 (pid: 3, stack limit = 0xda192238)
Also added a check for potential !runtime condition, commonly it is
done by PCM_RUNTIME_CHECK(substream) in the beginning, however this
does not completely prevent from oopses in u_audio_iso_complete(),
because the proper protection scheme must be implemented in PCM
library functions.
An example of *not fixed* oops due to substream->runtime->*
dereference by snd_pcm_running(substream) from
snd_pcm_period_elapsed(), where substream->runtime is gone while
waiting the substream lock:
Unable to handle kernel paging request at virtual address 6b6b6b6b
pgd = db7e4000
[6b6b6b6b] *pgd=00000000
CPU: 0 PID: 193 Comm: klogd Tainted: G C 3.14.54+ #118
task: db5ac500 ti: db60c000 task.ti: db60c000
PC is at snd_pcm_period_elapsed+0x48/0xd8 [snd_pcm]
LR is at snd_pcm_period_elapsed+0x40/0xd8 [snd_pcm]
pc : [<>] lr : [<>] psr: 60000193
Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user
Control: 10c5387d Table: 2b7e404a DAC: 00000015
Process klogd (pid: 193, stack limit = 0xdb60c238)
[<>] (snd_pcm_period_elapsed [snd_pcm]) from [<>] (udc_irq+0x500/0xbbc)
[<>] (udc_irq) from [<>] (ci_irq+0x280/0x304)
[<>] (ci_irq) from [<>] (handle_irq_event_percpu+0xa4/0x40c)
[<>] (handle_irq_event_percpu) from [<>] (handle_irq_event+0x3c/0x5c)
[<>] (handle_irq_event) from [<>] (handle_fasteoi_irq+0xc4/0x110)
[<>] (handle_fasteoi_irq) from [<>] (generic_handle_irq+0x20/0x30)
[<>] (generic_handle_irq) from [<>] (handle_IRQ+0x80/0xc0)
[<>] (handle_IRQ) from [<>] (gic_handle_irq+0x3c/0x60)
[<>] (gic_handle_irq) from [<>] (__irq_svc+0x44/0x78)
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx>
[erosca: W/o this patch, with minimal instrumentation [1], I can
consistently reproduce BUG: KASAN: use-after-free [2]]
[1] Instrumentation to reproduce issue [2]:
diff --git a/drivers/usb/gadget/function/u_audio.c b/drivers/usb/gadget/function/u_audio.c
index a72295c953bb..bd0b308024fe 100644
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -16,6 +16,7 @@
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
+#include <linux/delay.h>
#include "u_audio.h"
@@ -147,6 +148,8 @@ static void u_audio_iso_complete(struct usb_ep *ep, struct usb_request *req)
spin_unlock_irqrestore(&prm->lock, flags);
+ udelay(500); //delay here to increase probability of parallel activities
+
/* Pack USB load in ALSA ring buffer */
pending = prm->dma_bytes - hw_ptr;
[2] After applying [1], below BUG occurs on Rcar-H3-Salvator-X board:
==================================================================
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@xxxxxxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/function/u_audio.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
--- a/drivers/usb/gadget/function/u_audio.c
+++ b/drivers/usb/gadget/function/u_audio.c
@@ -25,6 +25,7 @@
#include <sound/core.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
+#include <linux/delay.h>
See a comment below...
#include "u_audio.h"
@@ -88,7 +89,7 @@ static const struct snd_pcm_hardware uac
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;
@@ -115,7 +116,14 @@ static void u_audio_iso_complete(struct
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) {
@@ -146,6 +154,8 @@ static void u_audio_iso_complete(struct
spin_unlock_irqrestore(&prm->lock, flags);
+ udelay(500); //delay here to increase probability of parallel activities
+
^^^^^
That part of the change came from the commit message, it just describes
instrumentation, and adding it to the change itself is wrong.
Note that the source commit 56bc61587daad does not have such issue.
--
Best wishes,
Vladimir
