WARNING: CPU: 1 PID: 813 at kernel/module.c:291 module_assert_mutex_or_preempt+0x49/0x90()

DISCUSSION poma 3 participants 4 messages Aug 10, 2015 – Aug 24, 2015 Media (V4L/DVB)

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poma

author

2015-08-10 21:26 UTC #0 lore raw

------------[ cut here ]------------
WARNING: CPU: 1 PID: 813 at kernel/module.c:291 module_assert_mutex_or_preempt+0x49/0x90()
Modules linked in: mxl5007t af9013 ... dvb_usb_af9015(+) ... dvb_usb_v2 dvb_core rc_core ...
CPU: 1 PID: 813 Comm: systemd-udevd Not tainted 4.2.0-0.rc6.git0.1.fc24.x86_64+debug #1
...
Call Trace:
 [<ffffffff81868d8e>] dump_stack+0x4c/0x65
 [<ffffffff810ab406>] warn_slowpath_common+0x86/0xc0
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff810ab53a>] warn_slowpath_null+0x1a/0x20
 [<ffffffff81150529>] module_assert_mutex_or_preempt+0x49/0x90
 [<ffffffff81150822>] __module_address+0x32/0x150
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff81150956>] __module_text_address+0x16/0x70
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff81150f19>] symbol_put_addr+0x29/0x40
 [<ffffffffa04b77ad>] dvb_frontend_detach+0x7d/0x90 [dvb_core]
 [<ffffffffa04cdfd5>] dvb_usbv2_probe+0xc85/0x11a0 [dvb_usb_v2]
 [<ffffffffa05607c4>] af9015_probe+0x84/0xf0 [dvb_usb_af9015]
 [<ffffffff8161c03b>] usb_probe_interface+0x1bb/0x2e0
 [<ffffffff81579f26>] driver_probe_device+0x1f6/0x450
 [<ffffffff8157a214>] __driver_attach+0x94/0xa0
 [<ffffffff8157a180>] ? driver_probe_device+0x450/0x450
 [<ffffffff815778f3>] bus_for_each_dev+0x73/0xc0
 [<ffffffff815796fe>] driver_attach+0x1e/0x20
 [<ffffffff8157922e>] bus_add_driver+0x1ee/0x280
 [<ffffffff8157b0a0>] driver_register+0x60/0xe0
 [<ffffffff8161a87d>] usb_register_driver+0xad/0x160
 [<ffffffffa0567000>] ? 0xffffffffa0567000
 [<ffffffffa056701e>] af9015_usb_driver_init+0x1e/0x1000 [dvb_usb_af9015]
 [<ffffffff81002123>] do_one_initcall+0xb3/0x200
 [<ffffffff8124ac65>] ? kmem_cache_alloc_trace+0x355/0x380
 [<ffffffff81867c37>] ? do_init_module+0x28/0x1e9
 [<ffffffff81867c6f>] do_init_module+0x60/0x1e9
 [<ffffffff81154167>] load_module+0x21f7/0x28d0
 [<ffffffff8114f600>] ? m_show+0x1b0/0x1b0
 [<ffffffff81026d79>] ? sched_clock+0x9/0x10
 [<ffffffff810e6ddc>] ? local_clock+0x1c/0x20
 [<ffffffff811549b8>] SyS_init_module+0x178/0x1c0
 [<ffffffff8187282e>] entry_SYSCALL_64_fastpath+0x12/0x76
---[ end trace 31a9dd90d4f559f5 ]---

Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1252167
https://bugzilla.kernel.org/show_bug.cgi?id=102631

poma

author

2015-08-21 10:21 UTC #1 lore raw

Quoted 47 lines · poma

------------[ cut here ]------------
WARNING: CPU: 1 PID: 813 at kernel/module.c:291 module_assert_mutex_or_preempt+0x49/0x90()
Modules linked in: mxl5007t af9013 ... dvb_usb_af9015(+) ... dvb_usb_v2 dvb_core rc_core ...
CPU: 1 PID: 813 Comm: systemd-udevd Not tainted 4.2.0-0.rc6.git0.1.fc24.x86_64+debug #1
...
Call Trace:
 [<ffffffff81868d8e>] dump_stack+0x4c/0x65
 [<ffffffff810ab406>] warn_slowpath_common+0x86/0xc0
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff810ab53a>] warn_slowpath_null+0x1a/0x20
 [<ffffffff81150529>] module_assert_mutex_or_preempt+0x49/0x90
 [<ffffffff81150822>] __module_address+0x32/0x150
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff81150956>] __module_text_address+0x16/0x70
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
 [<ffffffff81150f19>] symbol_put_addr+0x29/0x40
 [<ffffffffa04b77ad>] dvb_frontend_detach+0x7d/0x90 [dvb_core]
 [<ffffffffa04cdfd5>] dvb_usbv2_probe+0xc85/0x11a0 [dvb_usb_v2]
 [<ffffffffa05607c4>] af9015_probe+0x84/0xf0 [dvb_usb_af9015]
 [<ffffffff8161c03b>] usb_probe_interface+0x1bb/0x2e0
 [<ffffffff81579f26>] driver_probe_device+0x1f6/0x450
 [<ffffffff8157a214>] __driver_attach+0x94/0xa0
 [<ffffffff8157a180>] ? driver_probe_device+0x450/0x450
 [<ffffffff815778f3>] bus_for_each_dev+0x73/0xc0
 [<ffffffff815796fe>] driver_attach+0x1e/0x20
 [<ffffffff8157922e>] bus_add_driver+0x1ee/0x280
 [<ffffffff8157b0a0>] driver_register+0x60/0xe0
 [<ffffffff8161a87d>] usb_register_driver+0xad/0x160
 [<ffffffffa0567000>] ? 0xffffffffa0567000
 [<ffffffffa056701e>] af9015_usb_driver_init+0x1e/0x1000 [dvb_usb_af9015]
 [<ffffffff81002123>] do_one_initcall+0xb3/0x200
 [<ffffffff8124ac65>] ? kmem_cache_alloc_trace+0x355/0x380
 [<ffffffff81867c37>] ? do_init_module+0x28/0x1e9
 [<ffffffff81867c6f>] do_init_module+0x60/0x1e9
 [<ffffffff81154167>] load_module+0x21f7/0x28d0
 [<ffffffff8114f600>] ? m_show+0x1b0/0x1b0
 [<ffffffff81026d79>] ? sched_clock+0x9/0x10
 [<ffffffff810e6ddc>] ? local_clock+0x1c/0x20
 [<ffffffff811549b8>] SyS_init_module+0x178/0x1c0
 [<ffffffff8187282e>] entry_SYSCALL_64_fastpath+0x12/0x76
---[ end trace 31a9dd90d4f559f5 ]---

Quoted 4 lines

Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1252167
https://bugzilla.kernel.org/show_bug.cgi?id=102631

You guys are really something.

First of all, as is evident here, I am the original reporter, not Laura Abbott <[email protected]>.
-All- your comments including the final patch on this issue, are just plain wrong.[1]
This patch only hides the actual problem with this particular device - the dual tuner combination driven by dvb_usb_af9015 & mxl5007t, broken by design since day one.

Read the entire https://bugzilla.redhat.com/show_bug.cgi?id=1252167
and stop this nonsense.

NACK "module: Fix locking in symbol_put_addr()"

[1] http://www.gossamer-threads.com/lists/linux/kernel/2241154

Laura Abbott

2015-08-21 13:53 UTC #2 lore raw

Quoted 59 lines · poma

Quoted 47 lines · poma

------------[ cut here ]------------
WARNING: CPU: 1 PID: 813 at kernel/module.c:291 module_assert_mutex_or_preempt+0x49/0x90()
Modules linked in: mxl5007t af9013 ... dvb_usb_af9015(+) ... dvb_usb_v2 dvb_core rc_core ...
CPU: 1 PID: 813 Comm: systemd-udevd Not tainted 4.2.0-0.rc6.git0.1.fc24.x86_64+debug #1
...
Call Trace:
  [<ffffffff81868d8e>] dump_stack+0x4c/0x65
  [<ffffffff810ab406>] warn_slowpath_common+0x86/0xc0
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffff810ab53a>] warn_slowpath_null+0x1a/0x20
  [<ffffffff81150529>] module_assert_mutex_or_preempt+0x49/0x90
  [<ffffffff81150822>] __module_address+0x32/0x150
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffff81150956>] __module_text_address+0x16/0x70
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffffa057d0b0>] ? af9013_read_ucblocks+0x20/0x20 [af9013]
  [<ffffffff81150f19>] symbol_put_addr+0x29/0x40
  [<ffffffffa04b77ad>] dvb_frontend_detach+0x7d/0x90 [dvb_core]
  [<ffffffffa04cdfd5>] dvb_usbv2_probe+0xc85/0x11a0 [dvb_usb_v2]
  [<ffffffffa05607c4>] af9015_probe+0x84/0xf0 [dvb_usb_af9015]
  [<ffffffff8161c03b>] usb_probe_interface+0x1bb/0x2e0
  [<ffffffff81579f26>] driver_probe_device+0x1f6/0x450
  [<ffffffff8157a214>] __driver_attach+0x94/0xa0
  [<ffffffff8157a180>] ? driver_probe_device+0x450/0x450
  [<ffffffff815778f3>] bus_for_each_dev+0x73/0xc0
  [<ffffffff815796fe>] driver_attach+0x1e/0x20
  [<ffffffff8157922e>] bus_add_driver+0x1ee/0x280
  [<ffffffff8157b0a0>] driver_register+0x60/0xe0
  [<ffffffff8161a87d>] usb_register_driver+0xad/0x160
  [<ffffffffa0567000>] ? 0xffffffffa0567000
  [<ffffffffa056701e>] af9015_usb_driver_init+0x1e/0x1000 [dvb_usb_af9015]
  [<ffffffff81002123>] do_one_initcall+0xb3/0x200
  [<ffffffff8124ac65>] ? kmem_cache_alloc_trace+0x355/0x380
  [<ffffffff81867c37>] ? do_init_module+0x28/0x1e9
  [<ffffffff81867c6f>] do_init_module+0x60/0x1e9
  [<ffffffff81154167>] load_module+0x21f7/0x28d0
  [<ffffffff8114f600>] ? m_show+0x1b0/0x1b0
  [<ffffffff81026d79>] ? sched_clock+0x9/0x10
  [<ffffffff810e6ddc>] ? local_clock+0x1c/0x20
  [<ffffffff811549b8>] SyS_init_module+0x178/0x1c0
  [<ffffffff8187282e>] entry_SYSCALL_64_fastpath+0x12/0x76
---[ end trace 31a9dd90d4f559f5 ]---

Quoted 4 lines

Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1252167
https://bugzilla.kernel.org/show_bug.cgi?id=102631

You guys are really something.

Quoted 8 lines

Read the entire https://bugzilla.redhat.com/show_bug.cgi?id=1252167
and stop this nonsense.
NACK "module: Fix locking in symbol_put_addr()"
[1] http://www.gossamer-threads.com/lists/linux/kernel/2241154

Sorry, I've been delayed with conferences and have been avoiding e-mails and bugzilla. I missed sending out the Tested-by tag.
You are welcome to drop the reported-by if you don't think it is appropriate.

Laura

Rusty Russell

2015-08-24 01:18 UTC #3 lore raw

In reply to poma

Quoted 6 lines · poma

Quoted 4 lines
Ref.
https://bugzilla.redhat.com/show_bug.cgi?id=1252167
https://bugzilla.kernel.org/show_bug.cgi?id=102631
You guys are really something.

Hi Poma,

I understand your frustration!

I got involved via the other thread which didn't mention your bug report anywhere. I'm sure Laura was trying to be helpful by creating a minimal report, but the resulting patch erred in not crediting you.

Quoted 1 line

First of all, as is evident here, I am the original reporter, not Laura Abbott <[email protected]>.

Thanks for clarifying that. I have fixed the commit message to credit you. See below.

Quoted 3 lines

-All- your comments including the final patch on this issue, are just plain wrong.[1]
This patch only hides the actual problem with this particular device - the dual tuner combination driven by dvb_usb_af9015 & mxl5007t, broken by design since day one.

Oh, there's definitely a real issue in the driver; this one is cosmetic.

Quoted 4 lines

Read the entire https://bugzilla.redhat.com/show_bug.cgi?id=1252167
and stop this nonsense.
NACK "module: Fix locking in symbol_put_addr()"

Yeah, I've had days like this, too :(

Anyway, thanks for finding this bug: if the driver init hadn't been screwed it wouldn't have taken that path and found this for us.

Good luck with the other issue!
Rusty.

Quoted 1 line

From 275d7d44d802ef271a42dc87ac091a495ba72fc5 Mon Sep 17 00:00:00 2001

From: Peter Zijlstra <[email protected]>
Date: Thu, 20 Aug 2015 10:34:59 +0930
Subject: [PATCH] module: Fix locking in symbol_put_addr()

Poma (on the way to another bug) reported an assertion triggering:

  [<ffffffff81150529>] module_assert_mutex_or_preempt+0x49/0x90
  [<ffffffff81150822>] __module_address+0x32/0x150
  [<ffffffff81150956>] __module_text_address+0x16/0x70
  [<ffffffff81150f19>] symbol_put_addr+0x29/0x40
  [<ffffffffa04b77ad>] dvb_frontend_detach+0x7d/0x90 [dvb_core]

Laura Abbott <[email protected]> produced a patch which lead us to inspect symbol_put_addr(). This function has a comment claiming it doesn't need to disable preemption around the module lookup because it holds a reference to the module it wants to find, which therefore cannot go away.

This is wrong (and a false optimization too, preempt_disable() is really rather cheap, and I doubt any of this is on uber critical paths, otherwise it would've retained a pointer to the actual module anyway and avoided the second lookup).

While its true that the module cannot go away while we hold a reference on it, the data structure we do the lookup in very much _CAN_ change while we do the lookup. Therefore fix the comment and add the required preempt_disable().

Reported-by poma <[email protected]>

Signed-off-by Peter Zijlstra (Intel) <[email protected]>

Signed-off-by Rusty Russell <[email protected]>

Fixes a6e6abd575fc ("module: remove module_text_address()")

Cc [email protected]

kernel/module.c +6 -2

index b86b7bf1be38..8f051a106676 100644
@@ -1063,11 +1063,15 @@ void symbol_put_addr(void *addr)
 	if (core_kernel_text(a))
 		return;
 
-	/* module_text_address is safe here: we're supposed to have reference
-	 * to module from symbol_get, so it can't go away. */
+	/*
+	 * Even though we hold a reference on the module; we still need to
+	 * disable preemption in order to safely traverse the data structure.
+	 */
+	preempt_disable();
 	modaddr = __module_text_address(a);
 	BUG_ON(!modaddr);
 	module_put(modaddr);
+	preempt_enable();
 }
 EXPORT_SYMBOL_GPL(symbol_put_addr);