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Subject: Re: [PATCH] firewire: nosy: don't read packets bigger than requested
To:     Jann Horn <jannh@google.com>, stefanr@s5r6.in-berlin.de,
        linux1394-devel@lists.sourceforge.net
Cc:     kernel list <linux-kernel@vger.kernel.org>
References: <20180706151649.31119-1-jannh@google.com>
 <CAG48ez1etiHmD-e9szTEApia9YhUFomCcZM3Yp9wj9xrDWKmzg@mail.gmail.com>
From:   Randy Dunlap <rdunlap@infradead.org>
Message-ID: <cbf4c05d-94f2-6ef0-0c90-1f5823329bbb@infradead.org>
Date:   Mon, 3 Sep 2018 08:58:44 -0700
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On 09/03/2018 08:55 AM, Jann Horn wrote:
> On Fri, Jul 6, 2018 at 5:16 PM Jann Horn <jannh@google.com> wrote:
>> In general, accessing userspace memory beyond the length of the supplied
>> buffer in VFS read/write handlers can lead to both kernel memory corruption
>> (via kernel_read()/kernel_write(), which can e.g. be triggered via
>> sys_splice()) and privilege escalation inside userspace.
>>
>> Fixes: 286468210d83 ("firewire: new driver: nosy - IEEE 1394 traffic sniffer")
>> Signed-off-by: Jann Horn <jannh@google.com>
>> ---
>> No CC stable because this device shouldn't be available to unprivileged
>> code by default and should be pretty rare.
>>
>>  drivers/firewire/nosy.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/firewire/nosy.c b/drivers/firewire/nosy.c
>> index a128dd1126ae..732075fc312e 100644
>> --- a/drivers/firewire/nosy.c
>> +++ b/drivers/firewire/nosy.c
>> @@ -161,11 +161,12 @@ packet_buffer_get(struct client *client, char __user *data, size_t user_length)
>>         if (atomic_read(&buffer->size) == 0)
>>                 return -ENODEV;
>>
>> -       /* FIXME: Check length <= user_length. */
>> -
>>         end = buffer->data + buffer->capacity;
>>         length = buffer->head->length;
>>
>> +       if (length > user_length)
>> +               return -EINVAL;
>> +
>>         if (&buffer->head->data[length] < end) {
>>                 if (copy_to_user(data, buffer->head->data, length))
>>                         return -EFAULT;
> 
> Ping. I sent this about two months ago, I haven't received a reply,
> and from what I can tell, it hasn't landed in any tree so far...
> 

:(
I have that same problem with some Firewire documentation patches.
I plan to ask someone else to merge my patches.

-- 
~Randy