AcoSail/kernel_optimize_test
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exec: Factor unshare_sighand out of de_thread and call it separately

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This makes the code clearer and makes it easier to implement a mutex
that is not taken over any locations that may block indefinitely waiting
for userspace.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2020-03-25 10:00:21 -05:00
parent 2ca7be7d55
commit 0216915592
1 changed files with 26 additions and 13 deletions
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39
fs/exec.c
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@ -1194,6 +1194,23 @@ static int de_thread(struct task_struct *tsk)
flush_itimer_signals();
#endif
BUG_ON(!thread_group_leader(tsk));
return 0;
killed:
/* protects against exit_notify() and __exit_signal() */
read_lock(&tasklist_lock);
sig->group_exit_task = NULL;
sig->notify_count = 0;
read_unlock(&tasklist_lock);
return -EAGAIN;
}
static int unshare_sighand(struct task_struct *me)
{
struct sighand_struct *oldsighand = me->sighand;
if (refcount_read(&oldsighand->count) != 1) {
struct sighand_struct *newsighand;
/*
@ -1210,23 +1227,13 @@ static int de_thread(struct task_struct *tsk)
write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock);
rcu_assign_pointer(tsk->sighand, newsighand);
rcu_assign_pointer(me->sighand, newsighand);
spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock);
__cleanup_sighand(oldsighand);
}
BUG_ON(!thread_group_leader(tsk));
return 0;
killed:
/* protects against exit_notify() and __exit_signal() */
read_lock(&tasklist_lock);
sig->group_exit_task = NULL;
sig->notify_count = 0;
read_unlock(&tasklist_lock);
return -EAGAIN;
}
char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk)
@ -1264,13 +1271,19 @@ int flush_old_exec(struct linux_binprm * bprm)
int retval;
/*
* Make sure we have a private signal table and that
* we are unassociated from the previous thread group.
* Make this the only thread in the thread group.
*/
retval = de_thread(me);
if (retval)
goto out;
/*
* Make the signal table private.
*/
retval = unshare_sighand(me);
if (retval)
goto out;
/*
* Must be called _before_ exec_mmap() as bprm->mm is
* not visibile until then. This also enables the update