Re: [PATCH ghak90 (was ghak32) V4 01/10] audit: collect audit task parameters

Paul Moore
2019-01-03T20:10:31Z

On Thu, Nov 1, 2018 at 6:07 PM Richard Guy Briggs <rgb@redhat.com> wrote:
&gt; On 2018-10-19 19:15, Paul Moore wrote:
&gt; &gt; On Sun, Aug 5, 2018 at 4:32 AM Richard Guy Briggs
<rgb@redhat.com> wrote:
&gt; &gt; &gt; The audit-related parameters in struct task_struct
should ideally be
&gt; &gt; &gt; collected together and accessed through a standard audit API.
&gt; &gt; &gt;
&gt; &gt; &gt; Collect the existing loginuid, sessionid and
audit_context together in a
&gt; &gt; &gt; new struct audit_task_info called "audit" in struct task_struct.
&gt; &gt; &gt;
&gt; &gt; &gt; Use kmem_cache to manage this pool of memory.
&gt; &gt; &gt; Un-inline audit_free() to be able to always recover that memory.
&gt; &gt; &gt;
&gt; &gt; &gt; See: https://github.com/linux-audit/audit-kernel/issues/81
&gt; &gt; &gt;
&gt; &gt; &gt; Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
&gt; &gt; &gt; ---
&gt; &gt; &gt; include/linux/audit.h | 34 ++++++++++++++++++++++++----------
&gt; &gt; &gt; include/linux/sched.h | 5 +----
&gt; &gt; &gt; init/init_task.c | 3 +--
&gt; &gt; &gt; init/main.c | 2 ++
&gt; &gt; &gt; kernel/auditsc.c | 51
++++++++++++++++++++++++++++++++++++++++++---------
&gt; &gt; &gt; kernel/fork.c | 4 +++-
&gt; &gt; &gt; 6 files changed, 73 insertions(+), 26 deletions(-)
&gt; &gt;
&gt; &gt; ...
&gt; &gt;
&gt; &gt; &gt; diff --git a/include/linux/sched.h b/include/linux/sched.h
&gt; &gt; &gt; index 87bf02d..e117272 100644
&gt; &gt; &gt; --- a/include/linux/sched.h
&gt; &gt; &gt; +++ b/include/linux/sched.h
&gt; &gt; &gt; @@ -873,10 +872,8 @@ struct task_struct {
&gt; &gt; &gt;
&gt; &gt; &gt; struct callback_head *task_works;
&gt; &gt; &gt;
&gt; &gt; &gt; - struct audit_context *audit_context;
&gt; &gt; &gt; #ifdef CONFIG_AUDITSYSCALL
&gt; &gt; &gt; - kuid_t loginuid;
&gt; &gt; &gt; - unsigned int sessionid;
&gt; &gt; &gt; + struct audit_task_info *audit;
&gt; &gt; &gt; #endif
&gt; &gt; &gt; struct seccomp seccomp;
&gt; &gt;
&gt; &gt; Prior to this patch audit_context was available regardless of
&gt; &gt; CONFIG_AUDITSYSCALL, after this patch the corresponding audit_context
&gt; &gt; is only available when CONFIG_AUDITSYSCALL is defined.
&gt;
&gt; This was intentional since audit_context is not used when AUDITSYSCALL is
&gt; disabled. audit_alloc() was stubbed in that case to return 0.
audit_context()
&gt; returned NULL.
&gt;
&gt; The fact that audit_context was still present in struct task_struct was an
&gt; oversight in the two patches already accepted:
&gt; ("audit: use inline function to get audit context")
&gt; ("audit: use inline function to get audit context")
&gt; that failed to hide or remove it from struct task_struct when it
was no longer
&gt; relevant.

Okay, in that case let's pull this out and fix this separately from
the audit container ID patchset.

&gt; On further digging, loginuid and sessionid (and
audit_log_session_info) should
&gt; be part of CONFIG_AUDIT scope and not CONFIG_AUDITSYSCALL since
it is used in
&gt; CONFIG_CHANGE, ANOM_LINK, FEATURE_CHANGE(, INTEGRITY_RULE), none
of which are
&gt; otherwise dependent on AUDITSYSCALL.

This looks like something else we should fix independently from this patchset.

&gt; Looking ahead, contid should be treated like loginuid and
sessionid, which are
&gt; currently only available when syscall auditting is.

That seems reasonable. Eventually it would be great if we got rid of
CONFIG_AUDITSYSCALL, but that is a separate issue, and something that
is going to require work from the different arch/ABI folks to ensure
everything is working properly.

&gt; Converting records from standalone to syscall and checking
audit_dummy_context
&gt; changes the nature of CONFIG_AUDIT/!CONFIG_AUDITSYSCALL separation.
&gt; eg: ANOM_LINK accompanied by PATH record (which needed CWD addition to be
&gt; complete anyways)
&gt;
&gt; &gt; &gt; diff --git a/init/main.c b/init/main.c
&gt; &gt; &gt; index 3b4ada1..6aba171 100644
&gt; &gt; &gt; --- a/init/main.c
&gt; &gt; &gt; +++ b/init/main.c
&gt; &gt; &gt; @@ -92,6 +92,7 @@
&gt; &gt; &gt; #include <linux rodata_test.h="">
&gt; &gt; &gt; #include <linux jump_label.h="">
&gt; &gt; &gt; #include <linux mem_encrypt.h="">
&gt; &gt; &gt; +#include <linux audit.h="">
&gt; &gt; &gt;
&gt; &gt; &gt; #include <asm io.h="">
&gt; &gt; &gt; #include <asm bugs.h="">
&gt; &gt; &gt; @@ -721,6 +722,7 @@ asmlinkage __visible void __init
start_kernel(void)
&gt; &gt; &gt; nsfs_init();
&gt; &gt; &gt; cpuset_init();
&gt; &gt; &gt; cgroup_init();
&gt; &gt; &gt; + audit_task_init();
&gt; &gt; &gt; taskstats_init_early();
&gt; &gt; &gt; delayacct_init();
&gt; &gt;
&gt; &gt; It seems like we would need either init_struct_audit or
&gt; &gt; audit_task_init(), but not both, yes?
&gt;
&gt; One sets initial values of init task via an included struct,
other makes a call
&gt; to create the kmem cache. Both seem appropriate to me unless we move the
&gt; initialization from a struct to assignments in audit_task_init(),
but I'm not
&gt; that comfortable separating the audit init values from the rest of the
&gt; task_struct init task initializers (though there are other
subsystems that need
&gt; to do so dynamically).

My original thinking was focused on the use of init_struct_audit as an
initializer when audit_task_init() was already creating a kmem_cache
pool and a zero'd/init'd audit_task_info could be obtained via the
usual kmem_cache functions. Alternatively, although I don't believe
it would be recommended for this case, would be to use
init_struct_audit as an init helper if we included the audit_task_info
struct directly in the task_struct, as opposed to a pointer. What I
missed was the simple fact that you're only using init_struct_audit
for the init_task, which pretty much makes my original question rather
silly :)

--
paul moore