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51891498f2
The restriction introduced in 7a0df7fbc1 ("seccomp: Make NEW_LISTENER and
TSYNC flags exclusive") is mostly artificial: there is enough information
in a seccomp user notification to tell which thread triggered a
notification. The reason it was introduced is because TSYNC makes the
syscall return a thread-id on failure, and NEW_LISTENER returns an fd, and
there's no way to distinguish between these two cases (well, I suppose the
caller could check all fds it has, then do the syscall, and if the return
value was an fd that already existed, then it must be a thread id, but
bleh).
Matthew would like to use these two flags together in the Chrome sandbox
which wants to use TSYNC for video drivers and NEW_LISTENER to proxy
syscalls.
So, let's fix this ugliness by adding another flag, TSYNC_ESRCH, which
tells the kernel to just return -ESRCH on a TSYNC error. This way,
NEW_LISTENER (and any subsequent seccomp() commands that want to return
positive values) don't conflict with each other.
Suggested-by: Matthew Denton <mpdenton@google.com>
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Link: https://lore.kernel.org/r/20200304180517.23867-1-tycho@tycho.ws
Signed-off-by: Kees Cook <keescook@chromium.org>
117 lines
2.9 KiB
C
117 lines
2.9 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 <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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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 put_seccomp_filter(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 put_seccomp_filter(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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