Add in_execve flag into task_struct.

This patch allows LSM modules to determine whether current process is in an
execve operation or not so that they can behave differently while an execve
operation is in progress.

This patch is needed by TOMOYO. Please see another patch titled "LSM adapter
functions." for backgrounds.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

fs/compat.c

@@ -1402,6 +1402,7 @@ int compat_do_execve(char * filename,
 	retval = mutex_lock_interruptible(&current->cred_exec_mutex);
 	if (retval < 0)
 		goto out_free;
+	current->in_execve = 1;
 
 	retval = -ENOMEM;
 	bprm->cred = prepare_exec_creds();
@@ -1454,6 +1455,7 @@ int compat_do_execve(char * filename,
 		goto out;
 
 	/* execve succeeded */
+	current->in_execve = 0;
 	mutex_unlock(&current->cred_exec_mutex);
 	acct_update_integrals(current);
 	free_bprm(bprm);
@@ -1470,6 +1472,7 @@ out_file:
 	}
 
 out_unlock:
+	current->in_execve = 0;
 	mutex_unlock(&current->cred_exec_mutex);
 
 out_free:

fs/exec.c

@@ -1278,6 +1278,7 @@ int do_execve(char * filename,
 	retval = mutex_lock_interruptible(&current->cred_exec_mutex);
 	if (retval < 0)
 		goto out_free;
+	current->in_execve = 1;
 
 	retval = -ENOMEM;
 	bprm->cred = prepare_exec_creds();
@@ -1331,6 +1332,7 @@ int do_execve(char * filename,
 		goto out;
 
 	/* execve succeeded */
+	current->in_execve = 0;
 	mutex_unlock(&current->cred_exec_mutex);
 	acct_update_integrals(current);
 	free_bprm(bprm);
@@ -1349,6 +1351,7 @@ out_file:
 	}
 
 out_unlock:
+	current->in_execve = 0;
 	mutex_unlock(&current->cred_exec_mutex);
 
 out_free:

include/linux/sched.h

@@ -1158,6 +1158,8 @@ struct task_struct {
 	/* ??? */
 	unsigned int personality;
 	unsigned did_exec:1;
+	unsigned in_execve:1;	/* Tell the LSMs that the process is doing an
+				 * execve */
 	pid_t pid;
 	pid_t tgid;