On 9/4/2020 1:08 PM, Paul Moore wrote:
> On Wed, Aug 26, 2020 at 11:07 AM Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote:
>> Change the data used in UDS SO_PEERSEC processing from a
>> secid to a more general struct lsmblob. Update the
>> security_socket_getpeersec_dgram() interface to use the
>> lsmblob. There is a small amount of scaffolding code
>> that will come out when the security_secid_to_secctx()
>> code is brought in line with the lsmblob.
>>
>> Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>> ---
>> include/linux/security.h | 7 +++++--
>> include/net/af_unix.h | 2 +-
>> include/net/scm.h | 8 +++++---
>> net/ipv4/ip_sockglue.c | 8 +++++---
>> net/unix/af_unix.c | 6 +++---
>> security/security.c | 18 +++++++++++++++---
>> 6 files changed, 34 insertions(+), 15 deletions(-)
> ...
>
>> diff --git a/include/net/af_unix.h b/include/net/af_unix.h
>> index f42fdddecd41..a86da0cb5ec1 100644
>> --- a/include/net/af_unix.h
>> +++ b/include/net/af_unix.h
>> @@ -36,7 +36,7 @@ struct unix_skb_parms {
>> kgid_t gid;
>> struct scm_fp_list *fp; /* Passed files */
>> #ifdef CONFIG_SECURITY_NETWORK
>> - u32 secid; /* Security ID */
>> + struct lsmblob lsmblob; /* Security LSM data */
> As mentioned in a previous revision, I remain concerned that this is
> going to become a problem due to the size limit on unix_skb_parms. I
> would need to redo the math to be certain, but if I recall correctly
> this would limit us to five LSMs assuming both that we don't need to
> grow the per-LSM size of lsmblob *and* the netdev folks don't decide
> to add more fields to the unix_skb_parms.
>
> I lost track of that earlier discussion so I'm not sure where it ended
> up, but if there is a viable alternative it might be a good idea to
> pursue it.
Stephen had concerns about the lifecycle management involved. He also
pointed out that I had taken a cowards way out when allocations failed.
That could result in unexpected behavior when an allocation failed.
Fixing that would have required a major re-write of the currently simple
UDS attribute code, which I suspect would be as hard a sell to netdev as
expanding the secid to a lsmblob. I also thought I'd gotten netdev on the
CC: for this patch, but it looks like I missed it.
I did start on the UDS attribute re-do, and discovered that I was going
to have to introduce new failure paths, and that it might not be possible
to maintain compatibility for all cases because of the new possibilities
of failure.
