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SubjectRe: [RFC PATCH 1/2] autofs: set compat flag on sbi when daemon uses 32bit addressation
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14.09.2017 13:45, Ian Kent пишет:
> On 14/09/17 19:39, Stanislav Kinsburskiy wrote:
>>
>>
>> 14.09.2017 13:29, Ian Kent пишет:
>>> On 14/09/17 17:24, Stanislav Kinsburskiy wrote:
>>>>
>>>>
>>>> 14.09.2017 02:38, Ian Kent пишет:
>>>>> On 01/09/17 19:21, Stanislav Kinsburskiy wrote:
>>>>>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky@virtuozzo.com>
>>>>>> ---
>>>>>> fs/autofs4/autofs_i.h | 3 +++
>>>>>> fs/autofs4/dev-ioctl.c | 3 +++
>>>>>> fs/autofs4/inode.c | 4 +++-
>>>>>> 3 files changed, 9 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
>>>>>> index 4737615..3da105f 100644
>>>>>> --- a/fs/autofs4/autofs_i.h
>>>>>> +++ b/fs/autofs4/autofs_i.h
>>>>>> @@ -120,6 +120,9 @@ struct autofs_sb_info {
>>>>>> struct list_head active_list;
>>>>>> struct list_head expiring_list;
>>>>>> struct rcu_head rcu;
>>>>>> +#ifdef CONFIG_COMPAT
>>>>>> + unsigned is32bit:1;
>>>>>> +#endif
>>>>>> };
>>>>>>
>>>>>> static inline struct autofs_sb_info *autofs4_sbi(struct super_block *sb)
>>>>>> diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
>>>>>> index b7c816f..467d6c4 100644
>>>>>> --- a/fs/autofs4/dev-ioctl.c
>>>>>> +++ b/fs/autofs4/dev-ioctl.c
>>>>>> @@ -397,6 +397,9 @@ static int autofs_dev_ioctl_setpipefd(struct file *fp,
>>>>>> sbi->pipefd = pipefd;
>>>>>> sbi->pipe = pipe;
>>>>>> sbi->catatonic = 0;
>>>>>> +#ifdef CONFIG_COMPAT
>>>>>> + sbi->is32bit = is_compat_task();
>>>>>> +#endif
>>>>>> }
>>>>>> out:
>>>>>> put_pid(new_pid);
>>>>>> diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
>>>>>> index 09e7d68..21d3c0b 100644
>>>>>> --- a/fs/autofs4/inode.c
>>>>>> +++ b/fs/autofs4/inode.c
>>>>>> @@ -301,7 +301,9 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
>>>>>> } else {
>>>>>> sbi->oz_pgrp = get_task_pid(current, PIDTYPE_PGID);
>>>>>> }
>>>>>> -
>>>>>> +#ifdef CONFIG_COMPAT
>>>>>> + sbi->is32bit = is_compat_task();
>>>>>> +#endif
>>>>>> if (autofs_type_trigger(sbi->type))
>>>>>> __managed_dentry_set_managed(root);
>>>>>>
>>>>>>
>>>>>
>>>>> Not sure about this.
>>>>>
>>>>> Don't you think it would be better to avoid the in code #ifdefs by doing some
>>>>> checks and defines in the header file and defining what's need to just use
>>>>> is_compat_task().
>>>>>
>>>>
>>>> Yes, might be...
>>>>
>>>>> Not sure 2 patches are needed for this either ......
>>>>>
>>>>
>>>> Well, I found this issue occasionally.
>>>
>>> I'm wondering what the symptoms are?
>>>
>>
>> Size of struct autofs_v5_packet is 300 bytes for x86 and 304 bytes for x86_64.
>> Which means, that 32bit task can read more than size of autofs_v5_packet on 64bit kernel.
>
> Are you sure?
>
> Shouldn't that be a short read on the x86 side of a 4 bytes longer
> structure on the x86_64 side.
>
> I didn't think you could have a 64 bit client on a 32 bit kernel
> so the converse (the read past end of struct) doesn't apply.
>

Sorry for the confusion, I had to add brackets like this:

> Which means, that 32bit task can read more than size of autofs_v5_packet (on 64bit kernel).

IOW, 32bit task expects to read 300 bytes (size of struct autofs_v5_packet) while there are 304 bytes available on the "wire" from the 64bit kernel.


> Ian
>

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