[PATCH v14 22/23] LSM: Add /proc attr entry for full LSM context

[Stephen Smalley]

On 2/3/20 1:54 PM, Stephen Smalley wrote:
> I'd suggest something like the following instead:
> * @getprocattr
> *   Get the value of process attribute @name for task @p into a buffer
> *   allocated by the security module and returned via @value.  The
> *   caller will free the returned buffer via kfree.  The set of
> *   attribute names is fixed by proc but the format of @value is up
> *   to the security module authors except for the "context" attribute,
> *   whose value is required to be a NUL-terminated printable ASCII
> *   string without trailing whitespace.
> *   @p the task whose attribute is being fetched
> *   @name the name of the process attribute being fetched
> *   @value set to point to the buffer containing the attribute value
> *   Return the length of @value including the NUL on success, or -errno 
> on error.
> 
> The printable ASCII bit is based on what the dbus maintainer requested 
> in previous discussions.  The question of whether the terminating NUL 
> should be included in the returned length was otherwise left ambiguous 
> and inconsistent in your patch among the different security modules; if 
> you prefer not including it in the length returned by the security 
> modules, you'll need to adjust SELinux at least to not do so for "context".

BTW, I think the above guarantees with the exception of no trailing 
whitespace and whether the NUL byte is included or excluded from length 
are in reality also required for "current" (and SO_PEERSEC) or existing 
userspace will break.