[lkml]   [2002]   [Aug]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] Introduce BSD-style user credential [3/3]
>>>>> " " == Linus Torvalds <> writes:

> On Sat, 31 Aug 2002, Trond Myklebust wrote:
>> task-> ucred is not the unit for implementing shared creds
>> between threads.

> Fair enough, but some solution to this has to be found. I do
> not want to apply something that simply cannot work sanely, and
> I want to have at least a _plan_ on the table.

The plan is pretty rough at the moment, and not all of the code has
been written yet. Basically, it boils down to:

Add the COW structure 'vfs_cred'

Make VFS changes to replace all instances of
current->fsuid/fsgid/ngroups/groups with a single 'vfs_cred' that
never can be changed by CLONE_CRED after we call down into the VFS.
This means that we have to actually invent mechanisms for passing
those creds down to address_space_operations, inode_operations.

Add the more volatile 'pcred' a.k.a. 'task_cred' (see below), which
forms the necessary basis for CLONE_CRED tasks.

Audit 'task_cred' to ensure that CLONE_CRED won't introduce new
security holes. Things like capabilities, which can sometimes
override 'standard credentials', will for instance need to be looked

.... end of process -> add CLONE_CRED flag to 'clone()'

> This really ties in with the patches Dave has done (which are
> equivalent to your "pcred"), and I'd like to see them work
> together in practice.

Dave and I have already been discussing this on l-k, and we appear now
to be in agreement on general procedure. Dave has said that he'd like
to contribute once we get vfs_cred well established. I'm hoping he'll
help out on the latter too ;-)

> (I would suggest calling the FS credentials "struct vfs_cred",
> while the regular user credentials might just be "struct cred".
> Other suggestions?)

I'm fine about 'vfs'cred', but how about 'struct task_cred' instead
for the second? That ties them directly in to the task_struct, and
avoids people mistaking for 'ucred'. Since the distinction between COW
and non-COW is pretty profound, it might be useful in order to help
emphasize to which category they belong...

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:28    [W:0.112 / U:1.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site