linux-kernel - Re: [PATCH] ipmi: fix unsigned long underflow

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Message-ID: <145b74c4-24a6-5eb0-d193-80f74dd7e81e@acm.org>
Date:   Mon, 7 Aug 2017 07:24:32 -0500
From:   Corey Minyard <minyard@....org>
To:     Weilong Chen <chenweilong@...wei.com>
Cc:     openipmi-developer@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Corey Minyard <cminyard@...sta.com>
Subject: Re: [PATCH] ipmi: fix unsigned long underflow

On 08/07/2017 03:41 AM, Weilong Chen wrote:
> Hi Minyard,
>
> I test this patch, it works.
>
> Thanks.
>

Thanks, I added a Tested-by: for you and it's queued for the next release.
If it's urgent I can send it in now.

I also added this for the stable kernels 3.16 and later.

-corey

> On 2017/7/30 10:20, minyard@....org wrote:
>> From: Corey Minyard <cminyard@...sta.com>
>>
>> When I set the timeout to a specific value such as 500ms, the timeout
>> event will not happen in time due to the overflow in function
>> check_msg_timeout:
>> ...
>>     ent->timeout -= timeout_period;
>>     if (ent->timeout > 0)
>>         return;
>> ...
>>
>> The type of timeout_period is long, but ent->timeout is unsigned long.
>> This patch makes the type consistent.
>>
>> Reported-by: Weilong Chen <chenweilong@...wei.com>
>> Signed-off-by: Corey Minyard <cminyard@...sta.com>
>> ---
>> I like to keep things consistent (though I obviously messed up here)
>> and keep variables that should be positive unsigned.
>>
>> But you are right, there is a bug here and some inconsistency.
>> This patch changes timeout_period to be unsigned and fixes the
>> check.  Can you try this out?
>>
>>  drivers/char/ipmi/ipmi_msghandler.c | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/char/ipmi/ipmi_msghandler.c 
>> b/drivers/char/ipmi/ipmi_msghandler.c
>> index 810b138..c82d9fd 100644
>> --- a/drivers/char/ipmi/ipmi_msghandler.c
>> +++ b/drivers/char/ipmi/ipmi_msghandler.c
>> @@ -4030,7 +4030,8 @@ smi_from_recv_msg(ipmi_smi_t intf, struct 
>> ipmi_recv_msg *recv_msg,
>>  }
>>
>>  static void check_msg_timeout(ipmi_smi_t intf, struct seq_table *ent,
>> -                  struct list_head *timeouts, long timeout_period,
>> +                  struct list_head *timeouts,
>> +                  unsigned long timeout_period,
>>                    int slot, unsigned long *flags,
>>                    unsigned int *waiting_msgs)
>>  {
>> @@ -4043,8 +4044,8 @@ static void check_msg_timeout(ipmi_smi_t intf, 
>> struct seq_table *ent,
>>      if (!ent->inuse)
>>          return;
>>
>> -    ent->timeout -= timeout_period;
>> -    if (ent->timeout > 0) {
>> +    if (timeout_period < ent->timeout) {
>> +        ent->timeout -= timeout_period;
>>          (*waiting_msgs)++;
>>          return;
>>      }
>> @@ -4110,7 +4111,8 @@ static void check_msg_timeout(ipmi_smi_t intf, 
>> struct seq_table *ent,
>>      }
>>  }
>>
>> -static unsigned int ipmi_timeout_handler(ipmi_smi_t intf, long 
>> timeout_period)
>> +static unsigned int ipmi_timeout_handler(ipmi_smi_t intf,
>> +                     unsigned long timeout_period)
>>  {
>>      struct list_head     timeouts;
>>      struct ipmi_recv_msg *msg, *msg2;
>>
>