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SELinux: Don't flush inherited SIGKILL during execve()

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Don't flush inherited SIGKILL during execve() in SELinux's post cred commit
hook.  This isn't really a security problem: if the SIGKILL came before the
credentials were changed, then we were right to receive it at the time, and
should honour it; if it came after the creds were changed, then we definitely
should honour it; and in any case, all that will happen is that the process
will be scrapped before it ever returns to userspace.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
David Howells 2009-04-29 13:45:05 +01:00 committed by James Morris
parent 88c48db978
commit 3bcac0263f
3 changed files with 14 additions and 7 deletions
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1
include/linux/sched.h
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@ -1875,6 +1875,7 @@ extern void sched_dead(struct task_struct *p);
extern void proc_caches_init(void);
extern void flush_signals(struct task_struct *);
extern void __flush_signals(struct task_struct *);
extern void ignore_signals(struct task_struct *);
extern void flush_signal_handlers(struct task_struct *, int force_default);
extern int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info);

11
kernel/signal.c
View file

@ -238,14 +238,19 @@ void flush_sigqueue(struct sigpending *queue)
/*
* Flush all pending signals for a task.
*/
void __flush_signals(struct task_struct *t)
{
clear_tsk_thread_flag(t, TIF_SIGPENDING);
flush_sigqueue(&t->pending);
flush_sigqueue(&t->signal->shared_pending);
}
void flush_signals(struct task_struct *t)
{
unsigned long flags;
spin_lock_irqsave(&t->sighand->siglock, flags);
clear_tsk_thread_flag(t, TIF_SIGPENDING);
flush_sigqueue(&t->pending);
flush_sigqueue(&t->signal->shared_pending);
__flush_signals(t);
spin_unlock_irqrestore(&t->sighand->siglock, flags);
}

5
security/selinux/hooks.c
View file

@ -2394,11 +2394,12 @@ static void selinux_bprm_committed_creds(struct linux_binprm *bprm)
memset(&itimer, 0, sizeof itimer);
for (i = 0; i < 3; i++)
do_setitimer(i, &itimer, NULL);
flush_signals(current);
spin_lock_irq(&current->sighand->siglock);
if (!(current->signal->flags & SIGNAL_GROUP_EXIT)) {
__flush_signals(current);
flush_signal_handlers(current, 1);
sigemptyset(&current->blocked);
recalc_sigpending();
}
spin_unlock_irq(&current->sighand->siglock);
}