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Patch "usb: gadget: u_audio: protect stream runtime fields with stream spinlock" has been added to the 4.14-stable tree

DISCUSSION Vladimir Zapolskiy 2 participants 2 messages Aug 26, 2018 1 message not in the archive Stable branch

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Vladimir Zapolskiy

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#1 lore raw

Hi Greg,

Quoted 168 lines · On 08/26/2018 10:14 AM, [email protected] 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 <[email protected]> know about it.

From foo@baz Sun Aug 26 09:13:00 CEST 2018
From: Vladimir Zapolskiy <[email protected]>
Date: Thu, 21 Jun 2018 17:22:52 +0200
Subject: usb: gadget: u_audio: protect stream runtime fields with stream spinlock

From: Vladimir Zapolskiy <[email protected]>

[ 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 <[email protected]>

[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 <[email protected]>
Signed-off-by Felipe Balbi <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
  drivers/usb/gadget/function/u_audio.c |   13 ++++++++++++-
  1 file changed, 12 insertions(+), 1 deletion(-)

drivers/usb/gadget/function/u_audio.c line 29

Quoted 5 lines
drivers/usb/gadget/function/u_audio.c +1 -0
@@ -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...

Quoted 27 lines
drivers/usb/gadget/function/u_audio.c +8 -1
  #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) {

drivers/usb/gadget/function/u_audio.c static void u_audio_iso_complete(struct · line 158

Quoted 5 lines
drivers/usb/gadget/function/u_audio.c +2 -0
@@ -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

maintainer
#2 lore raw
Quoted 208 lines · Vladimir Zapolskiy

Hi Greg,

Quoted 168 lines · On 08/26/2018 10:14 AM, [email protected] 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 <[email protected]> know about it.

From foo@baz Sun Aug 26 09:13:00 CEST 2018
From: Vladimir Zapolskiy <[email protected]>
Date: Thu, 21 Jun 2018 17:22:52 +0200
Subject: usb: gadget: u_audio: protect stream runtime fields with stream spinlock

From: Vladimir Zapolskiy <[email protected]>

[ 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 <[email protected]>

[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 <[email protected]>
Signed-off-by Felipe Balbi <[email protected]>
Signed-off-by Sasha Levin <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
  drivers/usb/gadget/function/u_audio.c |   13 ++++++++++++-
  1 file changed, 12 insertions(+), 1 deletion(-)

drivers/usb/gadget/function/u_audio.c line 28

Quoted 4 lines
drivers/usb/gadget/function/u_audio.c +1 -0
@@ -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...

Quoted 24 lines
drivers/usb/gadget/function/u_audio.c +8 -1
  #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) {

drivers/usb/gadget/function/u_audio.c static void u_audio_iso_complete(struct · line 156

Quoted 3 lines
drivers/usb/gadget/function/u_audio.c +2 -0
@@ -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
+

^^^^^

Quoted 4 lines

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.

Ugh, that's a mess. I've fixed it up now, thanks for catching that. Putting diffs in a changelog text is a pain.

greg k-h