Re: [RFC PATCH v3] security, capability: pass object information to security_capable

[Stephen Smalley <sds@tycho.nsa.gov>]

On 8/15/19 6:32 PM, James Morris wrote:
> On Thu, 15 Aug 2019, Aaron Goidel wrote:
> 
>> In SELinux this new information is leveraged here to perform an
>> additional inode based check for capabilities relevant to inodes. Since
>> the inode provided to capable_wrt_inode_uidgid() is a const argument,
>> this also required propagating const down to dump_common_audit_data() and
>> dropping the use of d_find_alias() to find an alias for the inode. This
>> was sketchy to begin with and should be obsoleted by a separate change
>> that will allow LSMs to trigger audit collection for all file-related
>> information.
> 
> Will the audit logs look the same once the 2nd patch is applied? We need
> to be careful about breaking existing userland.

It was already the case that the name= field in the AVC audit record was 
not guaranteed to be emitted in this case, since d_find_alias could 
return NULL.  And it was only a hint, since that name might have nothing 
to do with the name used to look up the inode in the first place. So I 
don't believe userland could have ever relied upon it being present 
here.  Removing it also fixes a problem with AVC audit generation under 
RCU walk; we should be able to drop the code that skips audit generation 
in that case with this d_find_alias call gone IIUC.

With the ability for an LSM to enable collection and generation of 
AUDIT_PATH and other AUDIT_* records (which is made possible via the 
other patch), we will get more complete and relevant information in the 
audit log.  It won't look exactly the same (there will be separate AVC, 
PATH, ... records that can be correlated based on timestamp/serial and 
ausearch does this automatically for you).