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SubjectRe: [PATCH] firewire: nosy: don't read packets bigger than requested
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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

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