* question about fs sid
@ 2020-01-27 12:52 Dominick Grift
2020-01-27 13:55 ` Stephen Smalley
0 siblings, 1 reply; 3+ messages in thread
From: Dominick Grift @ 2020-01-27 12:52 UTC (permalink / raw)
To: selinux
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What is the fs sid used for exactly? What, if any, is its relationship with persistent file systems with xattr support.
Were currently associating a type that is generally also associated with persistent filesystems that support xattr but i dont know why.
Why would it not apply to other filesystems, for example tmpfs or vfat or whatever?
Is the fs sid still used and what do i need to consider when determining what context to associate with it?
--
gpg --locate-keys dominick.grift@defensec.nl
Key fingerprint = FCD2 3660 5D6B 9D27 7FC6 E0FF DA7E 521F 10F6 4098
Dominick Grift
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: question about fs sid
2020-01-27 12:52 question about fs sid Dominick Grift
@ 2020-01-27 13:55 ` Stephen Smalley
2020-01-27 14:08 ` Dominick Grift
0 siblings, 1 reply; 3+ messages in thread
From: Stephen Smalley @ 2020-01-27 13:55 UTC (permalink / raw)
To: selinux; +Cc: Dominick Grift
On 1/27/20 7:52 AM, Dominick Grift wrote:
> What is the fs sid used for exactly? What, if any, is its relationship with persistent file systems with xattr support.
> Were currently associating a type that is generally also associated with persistent filesystems that support xattr but i dont know why.
> Why would it not apply to other filesystems, for example tmpfs or vfat or whatever?
>
> Is the fs sid still used and what do i need to consider when determining what context to associate with it?
Are you referring to the fs initial SID, or to the SID associated with
each filesystem/superblock?
The former appears to be unused by any kernel code other than the
declaration (grep -r SECINITSID_FS). At one time, it was the default
SID to use for the filesystem/superblock. Looks like this has never
been used in mainline Linux, just pre-mainline SELinux. Sadly we cannot
just remove obsolete initial SIDs until we fix
https://github.com/SELinuxProject/selinux-kernel/issues/12
The latter is still relevant but the defaults are now determined through
fs_use_* or genfscon statements, default to the unlabeled SID if there
is no match, and can be overridden via the fscontext= mount option. It
is used in permission checks on the superblock/filesystem (e.g. mount,
unmount, ...) and to limit what file contexts can be assigned to files
within the filesystem (associate).
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: question about fs sid
2020-01-27 13:55 ` Stephen Smalley
@ 2020-01-27 14:08 ` Dominick Grift
0 siblings, 0 replies; 3+ messages in thread
From: Dominick Grift @ 2020-01-27 14:08 UTC (permalink / raw)
To: Stephen Smalley; +Cc: selinux
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On Mon, Jan 27, 2020 at 08:55:00AM -0500, Stephen Smalley wrote:
> On 1/27/20 7:52 AM, Dominick Grift wrote:
> > What is the fs sid used for exactly? What, if any, is its relationship with persistent file systems with xattr support.
> > Were currently associating a type that is generally also associated with persistent filesystems that support xattr but i dont know why.
> > Why would it not apply to other filesystems, for example tmpfs or vfat or whatever?
> >
> > Is the fs sid still used and what do i need to consider when determining what context to associate with it?
>
> Are you referring to the fs initial SID, or to the SID associated with each
> filesystem/superblock?
Thanks. Yes was referring to the fs initial sid.
I now moved it to the list of unused_isids. I'll see if that works
>
> The former appears to be unused by any kernel code other than the
> declaration (grep -r SECINITSID_FS). At one time, it was the default SID to
> use for the filesystem/superblock. Looks like this has never been used in
> mainline Linux, just pre-mainline SELinux. Sadly we cannot just remove
> obsolete initial SIDs until we fix
> https://github.com/SELinuxProject/selinux-kernel/issues/12
>
> The latter is still relevant but the defaults are now determined through
> fs_use_* or genfscon statements, default to the unlabeled SID if there is no
> match, and can be overridden via the fscontext= mount option. It is used in
> permission checks on the superblock/filesystem (e.g. mount, unmount, ...)
> and to limit what file contexts can be assigned to files within the
> filesystem (associate).
--
gpg --locate-keys dominick.grift@defensec.nl
Key fingerprint = FCD2 3660 5D6B 9D27 7FC6 E0FF DA7E 521F 10F6 4098
Dominick Grift
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
^ permalink raw reply [flat|nested] 3+ messages in thread
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