Cool. Sent.
> On Mar 25, 2015, at 4:09 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>
> On Wed, Mar 25, 2015 at 12:41:29PM -0400, Chengyu Song wrote:
>> There may be a simpler solution, declare NFSD_FAULT_INJECTION has dependency
>> on DEBUG_FS, or automatically select DEBUG_FS.
>
> Oh, I forgot about that--you're right, NFSD_FAULT_INJECTION isn't useful
> without DEBUG_FS anyway, so, sure, let's do that.
>
> --b.
>
>> I don't think current debugfs
>> implementation will return any error ptr once it's configured.
>>
>> I choose to check the return instead, because I was worried the debugfs interface
>> may change in the future.
>>
>> Does this sounds like a solution? If so, I can submit a patch for Kconfig.
>>
>> Best,
>> Chengyu
>>
>>> On Mar 25, 2015, at 11:17 AM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>>>
>>> On Mon, Mar 23, 2015 at 10:58:05PM -0400, Chengyu Song wrote:
>>>> debugfs_create_dir and debugfs_create_file may return -ENODEV when debugfs
>>>> is not configured, so the return value should be checked against ERROR_VALUE
>>>> as well, otherwise the later dereference of the dentry pointer would crash
>>>> the kernel.
>>>
>>> Thanks for spotting this. But it looks like this will cause nfsd
>>> startup to fail when debugfs isn't configured. I'd rather we didn't, it
>>> just isn't that important.
>>>
>>> So I'd rather just make nfsd_fault_inject_init() a void return--just do
>>> a dprintk as a warning in the "fail" case, and otherwise let normal
>>> startup continue (and check that doesn't lead to other unsafe
>>> dereferences of debug_dir). Could you try that?
>>>
>>> --b.
>>>
>>>
>>>>
>>>> Signed-off-by: Chengyu Song <csong84@xxxxxxxxxx>
>>>> ---
>>>> fs/nfsd/fault_inject.c | 12 ++++++++----
>>>> 1 file changed, 8 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/fs/nfsd/fault_inject.c b/fs/nfsd/fault_inject.c
>>>> index c16bf5a..621d065 100644
>>>> --- a/fs/nfsd/fault_inject.c
>>>> +++ b/fs/nfsd/fault_inject.c
>>>> @@ -132,19 +132,23 @@ int nfsd_fault_inject_init(void)
>>>> unsigned int i;
>>>> struct nfsd_fault_inject_op *op;
>>>> umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
>>>> + struct dentry *dent;
>>>>
>>>> - debug_dir = debugfs_create_dir("nfsd", NULL);
>>>> - if (!debug_dir)
>>>> + dent = debugfs_create_dir("nfsd", NULL);
>>>> + if (IS_ERR_OR_NULL(dent))
>>>> goto fail;
>>>> + debug_dir = dent;
>>>>
>>>> for (i = 0; i < NUM_INJECT_OPS; i++) {
>>>> op = &inject_ops[i];
>>>> - if (!debugfs_create_file(op->file, mode, debug_dir, op, &fops_nfsd))
>>>> + dent = debugfs_create_file(op->file, mode, debug_dir, op, &fops_nfsd);
>>>> + if (IS_ERR_OR_NULL(dent))
>>>> goto fail;
>>>> +
>>>> }
>>>> return 0;
>>>>
>>>> fail:
>>>> nfsd_fault_inject_cleanup();
>>>> - return -ENOMEM;
>>>> + return dent ? PTR_ERR(dent) : -ENOMEM;
>>>> }
>>>> --
>>>> 2.1.0
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