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3a15fb6ed9
The seccomp filter used to be released in free_task() which is called asynchronously via call_rcu() and assorted mechanisms. Since we need to inform tasks waiting on the seccomp notifier when a filter goes empty we will notify them as soon as a task has been marked fully dead in release_task(). To not split seccomp cleanup into two parts, move filter release out of free_task() and into release_task() after we've unhashed struct task from struct pid, exited signals, and unlinked it from the threadgroups' thread list. We'll put the empty filter notification infrastructure into it in a follow up patch. This also renames put_seccomp_filter() to seccomp_filter_release() which is a more descriptive name of what we're doing here especially once we've added the empty filter notification mechanism in there. We're also NULL-ing the task's filter tree entrypoint which seems cleaner than leaving a dangling pointer in there. Note that this shouldn't need any memory barriers since we're calling this when the task is in release_task() which means it's EXIT_DEAD. So it can't modify its seccomp filters anymore. You can also see this from the point where we're calling seccomp_filter_release(). It's after __exit_signal() and at this point, tsk->sighand will already have been NULLed which is required for thread-sync and filter installation alike. Cc: Tycho Andersen <tycho@tycho.ws> Cc: Kees Cook <keescook@chromium.org> Cc: Matt Denton <mpdenton@google.com> Cc: Sargun Dhillon <sargun@sargun.me> Cc: Jann Horn <jannh@google.com> Cc: Chris Palmer <palmer@google.com> Cc: Aleksa Sarai <cyphar@cyphar.com> Cc: Robert Sesek <rsesek@google.com> Cc: Jeffrey Vander Stoep <jeffv@google.com> Cc: Linux Containers <containers@lists.linux-foundation.org> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Link: https://lore.kernel.org/r/20200531115031.391515-2-christian.brauner@ubuntu.com Signed-off-by: Kees Cook <keescook@chromium.org>
118 lines
3 KiB
C
118 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_SECCOMP_H
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#define _LINUX_SECCOMP_H
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#include <uapi/linux/seccomp.h>
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#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \
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SECCOMP_FILTER_FLAG_LOG | \
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SECCOMP_FILTER_FLAG_SPEC_ALLOW | \
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SECCOMP_FILTER_FLAG_NEW_LISTENER | \
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SECCOMP_FILTER_FLAG_TSYNC_ESRCH)
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#ifdef CONFIG_SECCOMP
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#include <linux/thread_info.h>
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#include <linux/atomic.h>
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#include <asm/seccomp.h>
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struct seccomp_filter;
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/**
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* struct seccomp - the state of a seccomp'ed process
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*
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* @mode: indicates one of the valid values above for controlled
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* system calls available to a process.
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* @filter: must always point to a valid seccomp-filter or NULL as it is
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* accessed without locking during system call entry.
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*
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* @filter must only be accessed from the context of current as there
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* is no read locking.
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*/
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struct seccomp {
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int mode;
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atomic_t filter_count;
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struct seccomp_filter *filter;
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};
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#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
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extern int __secure_computing(const struct seccomp_data *sd);
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static inline int secure_computing(void)
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{
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if (unlikely(test_thread_flag(TIF_SECCOMP)))
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return __secure_computing(NULL);
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return 0;
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}
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#else
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extern void secure_computing_strict(int this_syscall);
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#endif
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extern long prctl_get_seccomp(void);
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extern long prctl_set_seccomp(unsigned long, void __user *);
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static inline int seccomp_mode(struct seccomp *s)
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{
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return s->mode;
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}
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#else /* CONFIG_SECCOMP */
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#include <linux/errno.h>
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struct seccomp { };
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struct seccomp_filter { };
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#ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER
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static inline int secure_computing(void) { return 0; }
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#else
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static inline void secure_computing_strict(int this_syscall) { return; }
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#endif
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static inline long prctl_get_seccomp(void)
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{
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return -EINVAL;
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}
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static inline long prctl_set_seccomp(unsigned long arg2, char __user *arg3)
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{
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return -EINVAL;
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}
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static inline int seccomp_mode(struct seccomp *s)
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{
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return SECCOMP_MODE_DISABLED;
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}
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#endif /* CONFIG_SECCOMP */
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#ifdef CONFIG_SECCOMP_FILTER
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extern void seccomp_filter_release(struct task_struct *tsk);
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extern void get_seccomp_filter(struct task_struct *tsk);
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#else /* CONFIG_SECCOMP_FILTER */
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static inline void seccomp_filter_release(struct task_struct *tsk)
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{
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return;
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}
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static inline void get_seccomp_filter(struct task_struct *tsk)
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{
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return;
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}
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#endif /* CONFIG_SECCOMP_FILTER */
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#if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
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extern long seccomp_get_filter(struct task_struct *task,
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unsigned long filter_off, void __user *data);
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extern long seccomp_get_metadata(struct task_struct *task,
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unsigned long filter_off, void __user *data);
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#else
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static inline long seccomp_get_filter(struct task_struct *task,
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unsigned long n, void __user *data)
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{
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return -EINVAL;
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}
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static inline long seccomp_get_metadata(struct task_struct *task,
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unsigned long filter_off,
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void __user *data)
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{
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return -EINVAL;
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}
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#endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */
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#endif /* _LINUX_SECCOMP_H */
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