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Message-ID: <51AC5F1B.4020409@cn.fujitsu.com>
Date: Mon, 03 Jun 2013 17:17:15 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Sören Brinkmann <soren.brinkmann@...inx.com>
CC: Michal Simek <michal.simek@...inx.com>,
Mike Turquette <mturquette@...aro.org>,
paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, git@...inx.com
Subject: [PATCH] clk: remove the clk_notifier from clk_notifier_list before
free it (was: Re: [BUG] zynq | CCF | SRCU)
On 06/01/2013 03:12 AM, Sören Brinkmann wrote:
> Hi,
>
> we recently encountered some kernel panics when we compiled one of our
> drivers as module and tested inserting/removing the module.
> Trying to debug this issue, I could reproduce it on the mainline kernel
> with a dummy module.
>
> What happens is, that when on driver remove clk_notifier_unregister() is
> called and no other notifier for that clock is registered, the kernel
> panics.
> I'm not sure what is going wrong here. If there is a bug (and if where)
> or I'm just using the infrastructure the wrong way,... So, any hint is
> appreciated.
>
> I attach the output from the crashing system. The stacktrace indicates a
> crash in 'srcu_readers_seq_idx()'.
> I also attach the module I used to trigger the issue and a patch on top
> of mainline commit a93cb29acaa8f75618c3f202d1cf43c231984644 which has
> the DT modifications I need to make the module find its clock and boot
> with my initramfs.
>
>
> Thanks,
> Sören
>
Hi, Sören Brinkmann
I guess:
modprobe clk_notif_dbg
modprobe clk_notif_dbg -r # memory corrupt here
modprobe clk_notif_dbg # access corrupted memroy, but no visiable bug
modprobe clk_notif_dbg -r # access corrupted memroy, BUG
How the first "modprobe clk_notif_dbg -r" corrupt memroy:
=========
int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
{
struct clk_notifier *cn = NULL;
int ret = -EINVAL;
if (!clk || !nb)
return -EINVAL;
clk_prepare_lock();
list_for_each_entry(cn, &clk_notifier_list, node)
if (cn->clk == clk)
break;
if (cn->clk == clk) {
ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
clk->notifier_count--;
/* XXX the notifier code should handle this better */
if (!cn->notifier_head.head) {
srcu_cleanup_notifier_head(&cn->notifier_head);
===========> the code forgot to remove @cn from the clk_notifier_list
===========> the second "modprobe clk_notif_dbg" will the same @clk and use the same corrupt @cn
kfree(cn);
}
} else {
ret = -ENOENT;
}
clk_prepare_unlock();
return ret;
}
===========
Could you retry with the following patch?
Thanks,
Lai
>From 5e26b626724139070148df9f6bd0607bc7bc3812 Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@...fujitsu.com>
Date: Mon, 3 Jun 2013 16:59:50 +0800
Subject: [PATCH] clk: remove the clk_notifier from clk_notifier_list before
free it
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
The @cn is stay in @clk_notifier_list after it is freed, it cause
memory corruption.
Example, if @clk is registered(first), unregistered(first),
registered(second), unregistered(second).
The freed @cn will be used when @clk is registered(second),
and the bug will be happened when @clk is unregistered(second):
[ 517.040000] clk_notif_dbg clk_notif_dbg.1: clk_notifier_unregister()
[ 517.040000] Unable to handle kernel paging request at virtual address 00df3008
[ 517.050000] pgd = ed858000
[ 517.050000] [00df3008] *pgd=00000000
[ 517.060000] Internal error: Oops: 5 [#1] PREEMPT SMP ARM
[ 517.060000] Modules linked in: clk_notif_dbg(O-) [last unloaded: clk_notif_dbg]
[ 517.060000] CPU: 1 PID: 499 Comm: modprobe Tainted: G O 3.10.0-rc3-00119-ga93cb29-dirty #85
[ 517.060000] task: ee1e0180 ti: ee3e6000 task.ti: ee3e6000
[ 517.060000] PC is at srcu_readers_seq_idx+0x48/0x84
[ 517.060000] LR is at srcu_readers_seq_idx+0x60/0x84
[ 517.060000] pc : [<c0052720>] lr : [<c0052738>] psr: 80070013
[ 517.060000] sp : ee3e7d48 ip : 00000000 fp : ee3e7d6c
[ 517.060000] r10: 00000000 r9 : ee3e6000 r8 : 00000000
[ 517.060000] r7 : ed84fe4c r6 : c068ec90 r5 : c068e430 r4 : 00000000
[ 517.060000] r3 : 00df3000 r2 : 00000000 r1 : 00000002 r0 : 00000000
[ 517.060000] Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 517.060000] Control: 18c5387d Table: 2d85804a DAC: 00000015
[ 517.060000] Process modprobe (pid: 499, stack limit = 0xee3e6238)
[ 517.060000] Stack: (0xee3e7d48 to 0xee3e8000)
....
[ 517.060000] [<c0052720>] (srcu_readers_seq_idx+0x48/0x84) from [<c0052790>] (try_check_zero+0x34/0xfc)
[ 517.060000] [<c0052790>] (try_check_zero+0x34/0xfc) from [<c00528b0>] (srcu_advance_batches+0x58/0x114)
[ 517.060000] [<c00528b0>] (srcu_advance_batches+0x58/0x114) from [<c0052c30>] (__synchronize_srcu+0x114/0x1ac)
[ 517.060000] [<c0052c30>] (__synchronize_srcu+0x114/0x1ac) from [<c0052d14>] (synchronize_srcu+0x2c/0x34)
[ 517.060000] [<c0052d14>] (synchronize_srcu+0x2c/0x34) from [<c0053a08>] (srcu_notifier_chain_unregister+0x68/0x74)
[ 517.060000] [<c0053a08>] (srcu_notifier_chain_unregister+0x68/0x74) from [<c0375a78>] (clk_notifier_unregister+0x7c/0xc0)
[ 517.060000] [<c0375a78>] (clk_notifier_unregister+0x7c/0xc0) from [<bf008034>] (clk_notif_dbg_remove+0x34/0x9c [clk_notif_dbg])
[ 517.060000] [<bf008034>] (clk_notif_dbg_remove+0x34/0x9c [clk_notif_dbg]) from [<c02bb974>] (platform_drv_remove+0x24/0x28)
[ 517.060000] [<c02bb974>] (platform_drv_remove+0x24/0x28) from [<c02b9bf8>] (__device_release_driver+0x8c/0xd4)
[ 517.060000] [<c02b9bf8>] (__device_release_driver+0x8c/0xd4) from [<c02ba680>] (driver_detach+0x9c/0xc4)
[ 517.060000] [<c02ba680>] (driver_detach+0x9c/0xc4) from [<c02b99c4>] (bus_remove_driver+0xcc/0xfc)
[ 517.060000] [<c02b99c4>] (bus_remove_driver+0xcc/0xfc) from [<c02bace4>] (driver_unregister+0x54/0x78)
[ 517.060000] [<c02bace4>] (driver_unregister+0x54/0x78) from [<c02bbb44>] (platform_driver_unregister+0x1c/0x20)
[ 517.060000] [<c02bbb44>] (platform_driver_unregister+0x1c/0x20) from [<bf0081f8>] (clk_notif_dbg_driver_exit+0x14/0x1c [clk_notif_dbg])
[ 517.060000] [<bf0081f8>] (clk_notif_dbg_driver_exit+0x14/0x1c [clk_notif_dbg]) from [<c00835e4>] (SyS_delete_module+0x200/0x28c)
[ 517.060000] [<c00835e4>] (SyS_delete_module+0x200/0x28c) from [<c000edc0>] (ret_fast_syscall+0x0/0x48)
[ 517.060000] Code: e5973004 e7911102 e0833001 e2881002 (e7933101)
CC: stable@...nel.org
Reported-by: Sören Brinkmann <soren.brinkmann@...inx.com>
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
drivers/clk/clk.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 934cfd1..1144e8c 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1955,6 +1955,7 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
/* XXX the notifier code should handle this better */
if (!cn->notifier_head.head) {
srcu_cleanup_notifier_head(&cn->notifier_head);
+ list_del(&cn->node);
kfree(cn);
}
--
1.7.4.4
--
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