Re: securityfs_create_dir strange comment

From: Jan Engelhardt
Date: Tue Feb 20 2007 - 18:46:55 EST

On Feb 20 2007 14:26, Greg KH wrote:
>On Tue, Feb 20, 2007 at 03:18:49PM -0600, Serge E. Hallyn wrote:
>> Quoting Jan Engelhardt (jengelh@xxxxxxxxxxxxxxx):
>> > Hello list,
>> >
>> >
>> > in security/inode.c, the comment for securityfs_create_dir() reads:
>> >
>> > If securityfs is not enabled in the kernel, the value -ENODEV
>> > will be returned. It is not wise to check for this value, but
>> > rather, check for NULL or !NULL instead as to eliminate the need
>> > for #ifdef in the calling code.
>> >
>> > What is the actual callee that can return NULL - and what should
>> > module_init() of a module return when securityfs_create_dir() returns
>> > NULL?
>> Hmm, this came from GregKH. It does seem based on the code that
>> checking for -ENODEV is necessary, so I don't understand the comment.
>If securityfs_create_dir() returns NULL, then something bad happened and
>your code needs to properly recover from it.
>Other than that, I don't understand the issue here.


static __init int mymodule_init(void)
struct dentry *de;
de = securityfs_create_dir("foobar", NULL);

/* case 1 */
return PTR_ERR(de);

/* case 2 */
if(de == NULL)
return WHAT_HERE; /* -EIO? */

There are two error cases. One: when the function gives us an error code.
Two: When it returns NULL, without an error code. This looks bogus to me.
What error is it, when there is no error? - And what should I return to
modprobe in that case?

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