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Date:   Fri, 31 Aug 2018 07:13:27 -0500
From:   Corey Minyard <minyard@....org>
To:     George Cherian <gcherian@...iumnetworks.com>,
        George Cherian <george.cherian@...ium.com>
Cc:     linux-kernel@...r.kernel.org,
        openipmi-developer@...ts.sourceforge.net,
        Corey Minyard <cminyard@...sta.com>
Subject: Re: [PATCH] ipmi: Fix I2C client removal in the SSIF driver

On 08/31/2018 06:58 AM, George Cherian wrote:
>
>
> On 08/30/2018 11:44 PM, minyard@....org wrote:
>>
>> From: Corey Minyard <cminyard@...sta.com>
>>
>> The SSIF driver was removing any client that came in through the
>> platform interface, but it should only remove clients that it
>> added.  On a failure in the probe function, this could result
>> in the following oops when the driver is removed and the
>> client gets unregistered twice:
>>
>>   CPU: 107 PID: 30266 Comm: rmmod Not tainted 4.18.0+ #80
>>   Hardware name: Cavium Inc. Saber/Saber, BIOS Cavium reference 
>> firmware version 7.0 08/04/2018
>>   pstate: 60400009 (nZCv daif +PAN -UAO)
>>   pc : kernfs_find_ns+0x28/0x120
>>   lr : kernfs_find_and_get_ns+0x40/0x60
>>   sp : ffff00002310fb50
>>   x29: ffff00002310fb50 x28: ffff800a8240f800
>>   x27: 0000000000000000 x26: 0000000000000000
>>   x25: 0000000056000000 x24: ffff000009073000
>>   x23: ffff000008998b38 x22: 0000000000000000
>>   x21: ffff800ed86de820 x20: 0000000000000000
>>   x19: ffff00000913a1d8 x18: 0000000000000000
>>   x17: 0000000000000000 x16: 0000000000000000
>>   x15: 0000000000000000 x14: 5300737265766972
>>   x13: 643d4d4554535953 x12: 0000000000000030
>>   x11: 0000000000000030 x10: 0101010101010101
>>   x9 : ffff800ea06cc3f9 x8 : 0000000000000000
>>   x7 : 0000000000000141 x6 : ffff000009073000
>>   x5 : ffff800adb706b00 x4 : 0000000000000000
>>   x3 : 00000000ffffffff x2 : 0000000000000000
>>   x1 : ffff000008998b38 x0 : ffff000008356760
>>   Process rmmod (pid: 30266, stack limit = 0x00000000e218418d)
>>   Call trace:
>>    kernfs_find_ns+0x28/0x120
>>    kernfs_find_and_get_ns+0x40/0x60
>>    sysfs_unmerge_group+0x2c/0x6c
>>    dpm_sysfs_remove+0x34/0x70
>>    device_del+0x58/0x30c
>>    device_unregister+0x30/0x7c
>>    i2c_unregister_device+0x84/0x90 [i2c_core]
>>    ssif_platform_remove+0x38/0x98 [ipmi_ssif]
>>    platform_drv_remove+0x2c/0x6c
>>    device_release_driver_internal+0x168/0x1f8
>>    driver_detach+0x50/0xbc
>>    bus_remove_driver+0x74/0xe8
>>    driver_unregister+0x34/0x5c
>>    platform_driver_unregister+0x20/0x2c
>>    cleanup_ipmi_ssif+0x50/0xd82c [ipmi_ssif]
>>    __arm64_sys_delete_module+0x1b4/0x220
>>    el0_svc_handler+0x104/0x160
>>    el0_svc+0x8/0xc
>>   Code: aa1e03e0 aa0203f6 aa0103f7 d503201f (7940e280)
>>   ---[ end trace 09f0e34cce8e2d8c ]---
>>   Kernel panic - not syncing: Fatal exception
>>   SMP: stopping secondary CPUs
>>   Kernel Offset: disabled
>>   CPU features: 0x23800c38
>>
>> So track the clients that the SSIF driver adds and only remove
>> those.
>>
>> Reported-by: George Cherian <george.cherian@...ium.com>
>> Signed-off-by: Corey Minyard <cminyard@...sta.com>
>> ---
>>   drivers/char/ipmi/ipmi_ssif.c | 17 ++++++-----------
>>   1 file changed, 6 insertions(+), 11 deletions(-)
>>
>> George, your fix was close, but not quite right.  The following
>> should fix the problem, obvious in hindsight :-).  Thanks for working
>> with me on this.
>>
> Thanks Corey!!!
> This works for me now.
>

Thanks.  Can I add a Tested-by: from you?

-corey

>> -corey
>>
>> diff --git a/drivers/char/ipmi/ipmi_ssif.c 
>> b/drivers/char/ipmi/ipmi_ssif.c
>> index e7e8b86..ca4f7c4 100644
>> --- a/drivers/char/ipmi/ipmi_ssif.c
>> +++ b/drivers/char/ipmi/ipmi_ssif.c
>> @@ -182,6 +182,8 @@ struct ssif_addr_info {
>>          struct device *dev;
>>          struct i2c_client *client;
>>
>> +       struct i2c_client *added_client;
>> +
>>          struct mutex clients_mutex;
>>          struct list_head clients;
>>
>> @@ -1639,15 +1641,7 @@ static int ssif_probe(struct i2c_client 
>> *client, const struct i2c_device_id *id)
>>
>>    out:
>>          if (rv) {
>> -               /*
>> -                * Note that if addr_info->client is assigned, we
>> -                * leave it.  The i2c client hangs around even if we
>> -                * return a failure here, and the failure here is not
>> -                * propagated back to the i2c code.  This seems to be
>> -                * design intent, strange as it may be.  But if we
>> -                * don't leave it, ssif_platform_remove will not remove
>> -                * the client like it should.
>> -                */
>> +               addr_info->client = NULL;
>>                  dev_err(&client->dev, "Unable to start IPMI SSIF: 
>> %d\n", rv);
>>                  kfree(ssif_info);
>>          }
>> @@ -1667,7 +1661,8 @@ static int ssif_adapter_handler(struct device 
>> *adev, void *opaque)
>>          if (adev->type != &i2c_adapter_type)
>>                  return 0;
>>
>> -       i2c_new_device(to_i2c_adapter(adev), &addr_info->binfo);
>> +       addr_info->added_client = i2c_new_device(to_i2c_adapter(adev),
>> + &addr_info->binfo);
>>
>>          if (!addr_info->adapter_name)
>>                  return 1; /* Only try the first I2C adapter by 
>> default. */
>> @@ -1840,7 +1835,7 @@ static int ssif_platform_remove(struct 
>> platform_device *dev)
>>                  return 0;
>>
>>          mutex_lock(&ssif_infos_mutex);
>> -       i2c_unregister_device(addr_info->client);
>> +       i2c_unregister_device(addr_info->added_client);
>>
>>          list_del(&addr_info->link);
>>          kfree(addr_info);
>> -- 
>> 2.7.4
>>

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