Getting vnode + credentials of a file from a struct mount and UFS inode #

[Matthew Fleming]

On Wed, Apr 13, 2011 at 3:25 PM, Jonathan Stuart <jstuart at adaranet.com> wrote:
> Hi,
>
> Yes, I am.. that was my suspicion (e.g., that it was the parameters of the process which called open()/creat()/socket()/... originally).  What's the quickest way to get back to the v/inode's uid/gid?
>

Since you have a struct mount * and an inode, it should be something like:

void
test_uidgid(struct mount *mp, ino_t ino)
{
	struct vnode *vp;
	struct inode *ip;
	int error;

	error = VFS_VGET(mp, ino, LK_SHARED, &vp);
	if (error != 0) {
		printf("Got error %d\n", error);
		return;
	}
	ip = VTOI(vp);
	printf("For inode %x, uid is %d, gid is %d\n", ino, ip->i_uid, ip->i_gid);
	vput(vp);
}

> Also, calling VFS_VGET() seems to give me a lockmgr panic with unknown type 0x0.
> What is odd is that the only way I can get a vnode for VFS_VGET is through struct file, and then shouldn't I be able to use that?  I tried using the flipping that vnode->inode with VTOI() and it was also giving me zeros for i_uid, i_gid, etc., when it shouldn't have been.
>

VFS_VGET gives you the vnode pointer; you shouldn't need getvnode() or
struct file or anything else.  There are other ways to get a vnode *,
but from an ino_t that's the easiest I know of.

Cheers,
matthew

> -----Original Message-----
> From: Matthew Fleming [mailto:mdf356 at gmail.com]
> Sent: Wednesday, April 13, 2011 3:20 PM
> To: Jonathan Stuart
> Cc: freebsd-hackers at freebsd.org
> Subject: Re: Getting vnode + credentials of a file from a struct mount and UFS inode #
>
> On Wed, Apr 13, 2011 at 2:37 PM, Jonathan Stuart <jstuart at adaranet.com> wrote:
>> Yes, however getvnode() does initialize a struct file *.. but f_cred seems to not contain valid/correct entries.
>> In my last post I probably should have pointed out that I have the inode stored from another operation.
>
> I haven't looked at this field before, but it looks that f_cred is set
> on falloc() to the cred of the thread creating the struct file (the
> thread that called open or socket or pipe or kqueue, etc.).  Are you
> running this as root/wheel?
>
> Cheers,
> matthew
>
>> -----Original Message-----
>> From: Matthew Fleming [mailto:mdf356 at gmail.com]
>> Sent: Wednesday, April 13, 2011 2:35 PM
>> To: Jonathan Stuart
>> Cc: freebsd-hackers at freebsd.org
>> Subject: Re: Getting vnode + credentials of a file from a struct mount and UFS inode #
>>
>> On Wed, Apr 13, 2011 at 2:18 PM, Jonathan Stuart <jstuart at adaranet.com> wrote:
>>> Hi Matthew,
>>>
>>> Thanks, I'll give it a shot.. for some reason f_cred off the vnode is returning all zeros for uid/gid, and
>>> pulling the VTOI does the same thing (using getvnode()).. do these not get initialized properly?
>>
>> f_cred is a field in struct file, not struct vnode, so I'm confused as
>> to what you're referring to.
>>
>> Cheers,
>> matthew
>>
>>> -----Original Message-----
>>> From: Matthew Fleming [mailto:mdf356 at gmail.com]
>>> Sent: Wednesday, April 13, 2011 1:48 PM
>>> To: Jonathan Stuart
>>> Cc: freebsd-hackers at freebsd.org
>>> Subject: Re: Getting vnode + credentials of a file from a struct mount and UFS inode #
>>>
>>> On Wed, Apr 13, 2011 at 12:31 PM, Jonathan Stuart <jstuart at adaranet.com> wrote:
>>>> Hi,
>>>>
>>>> I'd like to pull the owner/group ownership from a file (the information I have about the file is it's UFS inode # and it's struct mount *).  I'm sure there's got to be a function that would return a vnode and I could VTOI() to get this information from the inode.. but I'm having a brainfreeze.
>>>>
>>>
>>> VFS_VGET(mp, ino, flags, &vp) is probably what you want.
>>>
>>> Cheers,
>>> matthew
>>>
>>
>