seccomp: add SECCOMP_USER_NOTIF_FLAG_CONTINUE

[linux-block.git] / include / uapi / linux / seccomp.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _UAPI_LINUX_SECCOMP_H
#define _UAPI_LINUX_SECCOMP_H

#include <linux/compiler.h>
#include <linux/types.h>


/* Valid values for seccomp.mode and prctl(PR_SET_SECCOMP, <mode>) */
#define SECCOMP_MODE_DISABLED	0 /* seccomp is not in use. */
#define SECCOMP_MODE_STRICT	1 /* uses hard-coded filter. */
#define SECCOMP_MODE_FILTER	2 /* uses user-supplied filter. */

/* Valid operations for seccomp syscall. */
#define SECCOMP_SET_MODE_STRICT		0
#define SECCOMP_SET_MODE_FILTER		1
#define SECCOMP_GET_ACTION_AVAIL	2
#define SECCOMP_GET_NOTIF_SIZES		3

/* Valid flags for SECCOMP_SET_MODE_FILTER */
#define SECCOMP_FILTER_FLAG_TSYNC		(1UL << 0)
#define SECCOMP_FILTER_FLAG_LOG			(1UL << 1)
#define SECCOMP_FILTER_FLAG_SPEC_ALLOW		(1UL << 2)
#define SECCOMP_FILTER_FLAG_NEW_LISTENER	(1UL << 3)

/*
 * All BPF programs must return a 32-bit value.
 * The bottom 16-bits are for optional return data.
 * The upper 16-bits are ordered from least permissive values to most,
 * as a signed value (so 0x8000000 is negative).
 *
 * The ordering ensures that a min_t() over composed return values always
 * selects the least permissive choice.
 */
#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the process */
#define SECCOMP_RET_KILL_THREAD	 0x00000000U /* kill the thread */
#define SECCOMP_RET_KILL	 SECCOMP_RET_KILL_THREAD
#define SECCOMP_RET_TRAP	 0x00030000U /* disallow and force a SIGSYS */
#define SECCOMP_RET_ERRNO	 0x00050000U /* returns an errno */
#define SECCOMP_RET_USER_NOTIF	 0x7fc00000U /* notifies userspace */
#define SECCOMP_RET_TRACE	 0x7ff00000U /* pass to a tracer or disallow */
#define SECCOMP_RET_LOG		 0x7ffc0000U /* allow after logging */
#define SECCOMP_RET_ALLOW	 0x7fff0000U /* allow */

/* Masks for the return value sections. */
#define SECCOMP_RET_ACTION_FULL	0xffff0000U
#define SECCOMP_RET_ACTION	0x7fff0000U
#define SECCOMP_RET_DATA	0x0000ffffU

/**
 * struct seccomp_data - the format the BPF program executes over.
 * @nr: the system call number
 * @arch: indicates system call convention as an AUDIT_ARCH_* value
 *        as defined in <linux/audit.h>.
 * @instruction_pointer: at the time of the system call.
 * @args: up to 6 system call arguments always stored as 64-bit values
 *        regardless of the architecture.
 */
struct seccomp_data {
	int nr;
	__u32 arch;
	__u64 instruction_pointer;
	__u64 args[6];
};

struct seccomp_notif_sizes {
	__u16 seccomp_notif;
	__u16 seccomp_notif_resp;
	__u16 seccomp_data;
};

struct seccomp_notif {
	__u64 id;
	__u32 pid;
	__u32 flags;
	struct seccomp_data data;
};

/*
 * Valid flags for struct seccomp_notif_resp
 *
 * Note, the SECCOMP_USER_NOTIF_FLAG_CONTINUE flag must be used with caution!
 * If set by the process supervising the syscalls of another process the
 * syscall will continue. This is problematic because of an inherent TOCTOU.
 * An attacker can exploit the time while the supervised process is waiting on
 * a response from the supervising process to rewrite syscall arguments which
 * are passed as pointers of the intercepted syscall.
 * It should be absolutely clear that this means that the seccomp notifier
 * _cannot_ be used to implement a security policy! It should only ever be used
 * in scenarios where a more privileged process supervises the syscalls of a
 * lesser privileged process to get around kernel-enforced security
 * restrictions when the privileged process deems this safe. In other words,
 * in order to continue a syscall the supervising process should be sure that
 * another security mechanism or the kernel itself will sufficiently block
 * syscalls if arguments are rewritten to something unsafe.
 *
 * Similar precautions should be applied when stacking SECCOMP_RET_USER_NOTIF
 * or SECCOMP_RET_TRACE. For SECCOMP_RET_USER_NOTIF filters acting on the
 * same syscall, the most recently added filter takes precedence. This means
 * that the new SECCOMP_RET_USER_NOTIF filter can override any
 * SECCOMP_IOCTL_NOTIF_SEND from earlier filters, essentially allowing all
 * such filtered syscalls to be executed by sending the response
 * SECCOMP_USER_NOTIF_FLAG_CONTINUE. Note that SECCOMP_RET_TRACE can equally
 * be overriden by SECCOMP_USER_NOTIF_FLAG_CONTINUE.
 */
#define SECCOMP_USER_NOTIF_FLAG_CONTINUE BIT(0)

struct seccomp_notif_resp {
	__u64 id;
	__s64 val;
	__s32 error;
	__u32 flags;
};

#define SECCOMP_IOC_MAGIC		'!'
#define SECCOMP_IO(nr)			_IO(SECCOMP_IOC_MAGIC, nr)
#define SECCOMP_IOR(nr, type)		_IOR(SECCOMP_IOC_MAGIC, nr, type)
#define SECCOMP_IOW(nr, type)		_IOW(SECCOMP_IOC_MAGIC, nr, type)
#define SECCOMP_IOWR(nr, type)		_IOWR(SECCOMP_IOC_MAGIC, nr, type)

/* Flags for seccomp notification fd ioctl. */
#define SECCOMP_IOCTL_NOTIF_RECV	SECCOMP_IOWR(0, struct seccomp_notif)
#define SECCOMP_IOCTL_NOTIF_SEND	SECCOMP_IOWR(1,	\
						struct seccomp_notif_resp)
#define SECCOMP_IOCTL_NOTIF_ID_VALID	SECCOMP_IOR(2, __u64)
#endif /* _UAPI_LINUX_SECCOMP_H */