There may be a simpler solution, declare NFSD_FAULT_INJECTION has dependency
on DEBUG_FS, or automatically select DEBUG_FS. 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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