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Date:   Thu, 13 Aug 2020 13:08:49 -0400
From:   Josef Bacik <>
To:     David Laight <David.Laight@...LAB.COM>, "" <>,
        "" <>,
        "" <>,
        "" <>,
        "" <>
Subject: Re: [PATCH] proc: use vmalloc for our kernel buffer

On 8/13/20 12:19 PM, David Laight wrote:
> From: Josef Bacik
>> Sent: 13 August 2020 15:53
>>    sysctl: pass kernel pointers to ->proc_handler
>> we have been pre-allocating a buffer to copy the data from the proc
>> handlers into, and then copying that to userspace.  The problem is this
>> just blind kmalloc()'s the buffer size passed in from the read, which in
>> the case of our 'cat' binary was 64kib.  Order-4 allocations are not
>> awesome, and since we can potentially allocate up to our maximum order,
>> use vmalloc for these buffers.
> What happens if I run 'dd bs=16M ...' ?
> 	David

         /* don't even try if the size is too large */
         error = -ENOMEM;
         if (count >= KMALLOC_MAX_SIZE)
                 goto out;

is above this code, thanks,


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