linux-kernel - Re: [PATCH] proc: use vmalloc for our kernel buffer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <72ea0ff5-4706-d2e9-c2cf-c8827e576399@toxicpanda.com>
Date:   Thu, 13 Aug 2020 13:08:49 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     David Laight <David.Laight@...LAB.COM>, "hch@....de" <hch@....de>,
        "viro@...IV.linux.org.uk" <viro@...IV.linux.org.uk>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-team@...com" <kernel-team@...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,

Josef