diff mbox series

[RFC,3/6] security/fbfam: Use the api to manage statistics

Message ID 20200910202107.3799376-4-keescook@chromium.org
State New
Headers show
Series Fork brute force attack mitigation (fbfam) | expand

Commit Message

Kees Cook Sept. 10, 2020, 8:21 p.m. UTC
From: John Wood <john.wood@gmx.com>

Use the previous defined api to manage statistics calling it accordingly
when a task forks, calls execve or exits.

Signed-off-by: John Wood <john.wood@gmx.com>
---
 fs/exec.c     | 2 ++
 kernel/exit.c | 2 ++
 kernel/fork.c | 4 ++++
 3 files changed, 8 insertions(+)

Comments

Kees Cook Sept. 10, 2020, 11:33 p.m. UTC | #1
On Thu, Sep 10, 2020 at 01:21:04PM -0700, Kees Cook wrote:
> From: John Wood <john.wood@gmx.com>
> 
> Use the previous defined api to manage statistics calling it accordingly
> when a task forks, calls execve or exits.
> 
> Signed-off-by: John Wood <john.wood@gmx.com>
> ---
>  fs/exec.c     | 2 ++
>  kernel/exit.c | 2 ++
>  kernel/fork.c | 4 ++++
>  3 files changed, 8 insertions(+)
> 
> diff --git a/fs/exec.c b/fs/exec.c
> index a91003e28eaa..b30118674d32 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -71,6 +71,7 @@
>  #include "internal.h"
>  
>  #include <trace/events/sched.h>
> +#include <fbfam/fbfam.h>
>  
>  static int bprm_creds_from_file(struct linux_binprm *bprm);
>  
> @@ -1940,6 +1941,7 @@ static int bprm_execve(struct linux_binprm *bprm,
>  	task_numa_free(current, false);
>  	if (displaced)
>  		put_files_struct(displaced);
> +	fbfam_execve();

As mentioned in the other emails, I think this could trivially be
converted into an LSM: all the hooks are available AFAICT. If you only
want to introspect execve _happening_, you can use bprm_creds_for_exec
which is called a few lines above. Otherwise, my prior suggestion ("the
exec has happened" hook via brpm_cred_committing, etc).

>  	return retval;
>  
>  out:
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 733e80f334e7..39a6139dcf31 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -67,6 +67,7 @@
>  #include <linux/uaccess.h>
>  #include <asm/unistd.h>
>  #include <asm/mmu_context.h>
> +#include <fbfam/fbfam.h>
>  
>  static void __unhash_process(struct task_struct *p, bool group_dead)
>  {
> @@ -852,6 +853,7 @@ void __noreturn do_exit(long code)
>  		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
>  	exit_rcu();
>  	exit_tasks_rcu_finish();
> +	fbfam_exit();
>  
>  	lockdep_free_task(tsk);
>  	do_task_dead();

The place for this would be put_task_struct, and the LSM hook is
task_free. :) (The only caveat with task_free hook is that it may be
called in non-process context due to being freed during RCU, etc. In
practice, this is unlikely to cause problems.)

> diff --git a/kernel/fork.c b/kernel/fork.c
> index 49677d668de4..c933838450a8 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -107,6 +107,8 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/task.h>
>  
> +#include <fbfam/fbfam.h>
> +
>  /*
>   * Minimum number of threads to boot the kernel
>   */
> @@ -941,6 +943,8 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
>  #ifdef CONFIG_MEMCG
>  	tsk->active_memcg = NULL;
>  #endif
> +
> +	fbfam_fork(tsk);
>  	return tsk;

Since you don't need "orig", this is also trivially an LSM hook.
dup_task_struct() is called by copy_process(), which will also call the
task_alloc LSM hook later on.

>  
>  free_stack:
> -- 
> 2.25.1
>
Steven Rostedt Sept. 29, 2020, 11:47 p.m. UTC | #2
On Thu, 10 Sep 2020 16:33:38 -0700
Kees Cook <keescook@chromium.org> wrote:

> > @@ -1940,6 +1941,7 @@ static int bprm_execve(struct linux_binprm *bprm,
> >  	task_numa_free(current, false);
> >  	if (displaced)
> >  		put_files_struct(displaced);
> > +	fbfam_execve();  
> 
> As mentioned in the other emails, I think this could trivially be
> converted into an LSM: all the hooks are available AFAICT. If you only
> want to introspect execve _happening_, you can use bprm_creds_for_exec
> which is called a few lines above. Otherwise, my prior suggestion ("the
> exec has happened" hook via brpm_cred_committing, etc).

And if its information only, you could just register a callback to the
trace_sched_process_exec() tracepoint and do whatever you want then.

The tracepoints are available for anyone to attach to. Not just tracing.

-- Steve
Steven Rostedt Sept. 29, 2020, 11:49 p.m. UTC | #3
On Tue, 29 Sep 2020 19:47:12 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Thu, 10 Sep 2020 16:33:38 -0700
> Kees Cook <keescook@chromium.org> wrote:
> 
> > > @@ -1940,6 +1941,7 @@ static int bprm_execve(struct linux_binprm *bprm,
> > >  	task_numa_free(current, false);
> > >  	if (displaced)
> > >  		put_files_struct(displaced);
> > > +	fbfam_execve();    
> > 
> > As mentioned in the other emails, I think this could trivially be
> > converted into an LSM: all the hooks are available AFAICT. If you only
> > want to introspect execve _happening_, you can use bprm_creds_for_exec
> > which is called a few lines above. Otherwise, my prior suggestion ("the
> > exec has happened" hook via brpm_cred_committing, etc).  
> 
> And if its information only, you could just register a callback to the
> trace_sched_process_exec() tracepoint and do whatever you want then.
> 
> The tracepoints are available for anyone to attach to. Not just tracing.
> 

And there's also trace_sched_process_fork() and
trace_sched_process_exit().

-- Steve
John Wood Oct. 3, 2020, 9:52 a.m. UTC | #4
Hi Steven,

On Tue, Sep 29, 2020 at 07:49:24PM -0400, Steven Rostedt wrote:
> On Tue, 29 Sep 2020 19:47:12 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > On Thu, 10 Sep 2020 16:33:38 -0700
> > Kees Cook <keescook@chromium.org> wrote:
> >
> > > > @@ -1940,6 +1941,7 @@ static int bprm_execve(struct linux_binprm *bprm,
> > > >  	task_numa_free(current, false);
> > > >  	if (displaced)
> > > >  		put_files_struct(displaced);
> > > > +	fbfam_execve();
> > >
> > > As mentioned in the other emails, I think this could trivially be
> > > converted into an LSM: all the hooks are available AFAICT. If you only
> > > want to introspect execve _happening_, you can use bprm_creds_for_exec
> > > which is called a few lines above. Otherwise, my prior suggestion ("the
> > > exec has happened" hook via brpm_cred_committing, etc).
> >
> > And if its information only, you could just register a callback to the
> > trace_sched_process_exec() tracepoint and do whatever you want then.
> >
> > The tracepoints are available for anyone to attach to. Not just tracing.
> >
> And there's also trace_sched_process_fork() and
> trace_sched_process_exit().

Since this feature requires a pointer to the statistical data in the
task_struct structure, and the LSM allows this using the security blobs,
I think that the best for now is convert all the code to an LSM. Anyway,
thanks for the suggestion.

> -- Steve

Thanks,
John Wood
diff mbox series

Patch

diff --git a/fs/exec.c b/fs/exec.c
index a91003e28eaa..b30118674d32 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -71,6 +71,7 @@ 
 #include "internal.h"
 
 #include <trace/events/sched.h>
+#include <fbfam/fbfam.h>
 
 static int bprm_creds_from_file(struct linux_binprm *bprm);
 
@@ -1940,6 +1941,7 @@  static int bprm_execve(struct linux_binprm *bprm,
 	task_numa_free(current, false);
 	if (displaced)
 		put_files_struct(displaced);
+	fbfam_execve();
 	return retval;
 
 out:
diff --git a/kernel/exit.c b/kernel/exit.c
index 733e80f334e7..39a6139dcf31 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -67,6 +67,7 @@ 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
 #include <asm/mmu_context.h>
+#include <fbfam/fbfam.h>
 
 static void __unhash_process(struct task_struct *p, bool group_dead)
 {
@@ -852,6 +853,7 @@  void __noreturn do_exit(long code)
 		__this_cpu_add(dirty_throttle_leaks, tsk->nr_dirtied);
 	exit_rcu();
 	exit_tasks_rcu_finish();
+	fbfam_exit();
 
 	lockdep_free_task(tsk);
 	do_task_dead();
diff --git a/kernel/fork.c b/kernel/fork.c
index 49677d668de4..c933838450a8 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -107,6 +107,8 @@ 
 #define CREATE_TRACE_POINTS
 #include <trace/events/task.h>
 
+#include <fbfam/fbfam.h>
+
 /*
  * Minimum number of threads to boot the kernel
  */
@@ -941,6 +943,8 @@  static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 #ifdef CONFIG_MEMCG
 	tsk->active_memcg = NULL;
 #endif
+
+	fbfam_fork(tsk);
 	return tsk;
 
 free_stack: