Re: [PATCH] printk: ringbuffer: Wrong data pointer when appending small string

[John Ogness]

On 2020-10-15, Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> wrote:
>> diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c
>> index 2493348a1631..24a960a89aa8 100644
>> --- a/kernel/printk/printk_ringbuffer.c
>> +++ b/kernel/printk/printk_ringbuffer.c
>> @@ -1125,7 +1125,10 @@ static char *data_realloc(struct printk_ringbuffer *rb,
>>  
>>  	/* If the data block does not increase, there is nothing to do. */
>>  	if (head_lpos - next_lpos < DATA_SIZE(data_ring)) {
>> -		blk = to_block(data_ring, blk_lpos->begin);
>> +		if (wrapped)
>> +			blk = to_block(data_ring, 0);
>> +		else
>> +			blk = to_block(data_ring, blk_lpos->begin);
>>  		return &blk->data[0];
>>  	}
>
> Great catch.

Indeed. I don't know how we missed that one. :-/

Reviewed-by: John Ogness <john.ogness@xxxxxxxxxxxxx>