linux-kernel - Re: [PATCH][next] dm ioctl: rate limit a couple of ioctl based error messages

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Message-ID: <363880be-dfa3-4cfc-8d7d-613092c36dd0@gmail.com>
Date: Thu, 24 Oct 2024 15:05:34 +0100
From: "Colin King (gmail)" <colin.i.king@...il.com>
To: Mikulas Patocka <mpatocka@...hat.com>
Cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>,
 dm-devel@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] dm ioctl: rate limit a couple of ioctl based error
 messages

On 24/10/2024 15:01, Mikulas Patocka wrote:
> Hi
> 
> I'd like to ask - have you experienced these errors? What was the process
> that triggered them? Was it some robot that tests syscalls with random
> parameters?

I hit this when running stress-ng's dev test, this exercises various 
ioctls for race conditions.  It's not a major issue, just a corner case 
found when I was running some stress tests.

Colin

> 
> Mikulas
> 
> 
> On Thu, 24 Oct 2024, Colin Ian King wrote:
> 
>> It is possible to spam the kernel log with a misbehaving user process that
>> is passing incorrect dm ioctls to /dev/mapper/control. Use a rate limit
>> on these error messages to reduce the noise.
>>
>> Signed-off-by: Colin Ian King <colin.i.king@...il.com>
>> ---
>>   drivers/md/dm-ioctl.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
>> index f299ff393a6a..d42eac944eb5 100644
>> --- a/drivers/md/dm-ioctl.c
>> +++ b/drivers/md/dm-ioctl.c
>> @@ -1912,7 +1912,7 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user,
>>   
>>   	if ((kernel_params->version[0] != DM_VERSION_MAJOR) ||
>>   	    (kernel_params->version[1] > DM_VERSION_MINOR)) {
>> -		DMERR("ioctl interface mismatch: kernel(%u.%u.%u), user(%u.%u.%u), cmd(%d)",
>> +		DMERR_LIMIT("ioctl interface mismatch: kernel(%u.%u.%u), user(%u.%u.%u), cmd(%d)",
>>   		      DM_VERSION_MAJOR, DM_VERSION_MINOR,
>>   		      DM_VERSION_PATCHLEVEL,
>>   		      kernel_params->version[0],
>> @@ -1961,7 +1961,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
>>   
>>   	if (unlikely(param_kernel->data_size < minimum_data_size) ||
>>   	    unlikely(param_kernel->data_size > DM_MAX_TARGETS * DM_MAX_TARGET_PARAMS)) {
>> -		DMERR("Invalid data size in the ioctl structure: %u",
>> +		DMERR_LIMIT("Invalid data size in the ioctl structure: %u",
>>   		      param_kernel->data_size);
>>   		return -EINVAL;
>>   	}
>> -- 
>> 2.39.5
>>
>