[mirror_ubuntu-bionic-kernel.git] / kernel / seccomp.c

/*
 * linux/kernel/seccomp.c
 *
 * Copyright 2004-2005  Andrea Arcangeli <andrea@cpushare.com>
 *
 * Copyright (C) 2012 Google, Inc.
 * Will Drewry <wad@chromium.org>
 *
 * This defines a simple but solid secure-computing facility.
 *
 * Mode 1 uses a fixed list of allowed system calls.
 * Mode 2 allows user-defined system call filters in the form
 *        of Berkeley Packet Filters/Linux Socket Filters.
 */

#include <linux/atomic.h>
#include <linux/audit.h>
#include <linux/compat.h>
#include <linux/sched.h>
#include <linux/seccomp.h>

/* #define SECCOMP_DEBUG 1 */

#ifdef CONFIG_SECCOMP_FILTER
#include <asm/syscall.h>
#include <linux/filter.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/tracehook.h>
#include <linux/uaccess.h>

/**
 * struct seccomp_filter - container for seccomp BPF programs
 *
 * @usage: reference count to manage the object lifetime.
 *         get/put helpers should be used when accessing an instance
 *         outside of a lifetime-guarded section.  In general, this
 *         is only needed for handling filters shared across tasks.
 * @prev: points to a previously installed, or inherited, filter
 * @len: the number of instructions in the program
 * @insns: the BPF program instructions to evaluate
 *
 * seccomp_filter objects are organized in a tree linked via the @prev
 * pointer.  For any task, it appears to be a singly-linked list starting
 * with current->seccomp.filter, the most recently attached or inherited filter.
 * However, multiple filters may share a @prev node, by way of fork(), which
 * results in a unidirectional tree existing in memory.  This is similar to
 * how namespaces work.
 *
 * seccomp_filter objects should never be modified after being attached
 * to a task_struct (other than @usage).
 */
struct seccomp_filter {
	atomic_t usage;
	struct seccomp_filter *prev;
	unsigned short len;  /* Instruction count */
	struct sock_filter insns[];
};

/* Limit any path through the tree to 256KB worth of instructions. */
#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))

/**
 * get_u32 - returns a u32 offset into data
 * @data: a unsigned 64 bit value
 * @index: 0 or 1 to return the first or second 32-bits
 *
 * This inline exists to hide the length of unsigned long.  If a 32-bit
 * unsigned long is passed in, it will be extended and the top 32-bits will be
 * 0. If it is a 64-bit unsigned long, then whatever data is resident will be
 * properly returned.
 *
 * Endianness is explicitly ignored and left for BPF program authors to manage
 * as per the specific architecture.
 */
static inline u32 get_u32(u64 data, int index)
{
	return ((u32 *)&data)[index];
}

/* Helper for bpf_load below. */
#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
/**
 * bpf_load: checks and returns a pointer to the requested offset
 * @off: offset into struct seccomp_data to load from
 *
 * Returns the requested 32-bits of data.
 * seccomp_check_filter() should assure that @off is 32-bit aligned
 * and not out of bounds.  Failure to do so is a BUG.
 */
u32 seccomp_bpf_load(int off)
{
	struct pt_regs *regs = task_pt_regs(current);
	if (off == BPF_DATA(nr))
		return syscall_get_nr(current, regs);
	if (off == BPF_DATA(arch))
		return syscall_get_arch(current, regs);
	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
		unsigned long value;
		int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
		int index = !!(off % sizeof(u64));
		syscall_get_arguments(current, regs, arg, 1, &value);
		return get_u32(value, index);
	}
	if (off == BPF_DATA(instruction_pointer))
		return get_u32(KSTK_EIP(current), 0);
	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
		return get_u32(KSTK_EIP(current), 1);
	/* seccomp_check_filter should make this impossible. */
	BUG();
}

/**
 *	seccomp_check_filter - verify seccomp filter code
 *	@filter: filter to verify
 *	@flen: length of filter
 *
 * Takes a previously checked filter (by sk_chk_filter) and
 * redirects all filter code that loads struct sk_buff data
 * and related data through seccomp_bpf_load.  It also
 * enforces length and alignment checking of those loads.
 *
 * Returns 0 if the rule set is legal or -EINVAL if not.
 */
static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
{
	int pc;
	for (pc = 0; pc < flen; pc++) {
		struct sock_filter *ftest = &filter[pc];
		u16 code = ftest->code;
		u32 k = ftest->k;

		switch (code) {
		case BPF_S_LD_W_ABS:
			ftest->code = BPF_S_ANC_SECCOMP_LD_W;
			/* 32-bit aligned and not out of bounds. */
			if (k >= sizeof(struct seccomp_data) || k & 3)
				return -EINVAL;
			continue;
		case BPF_S_LD_W_LEN:
			ftest->code = BPF_S_LD_IMM;
			ftest->k = sizeof(struct seccomp_data);
			continue;
		case BPF_S_LDX_W_LEN:
			ftest->code = BPF_S_LDX_IMM;
			ftest->k = sizeof(struct seccomp_data);
			continue;
		/* Explicitly include allowed calls. */
		case BPF_S_RET_K:
		case BPF_S_RET_A:
		case BPF_S_ALU_ADD_K:
		case BPF_S_ALU_ADD_X:
		case BPF_S_ALU_SUB_K:
		case BPF_S_ALU_SUB_X:
		case BPF_S_ALU_MUL_K:
		case BPF_S_ALU_MUL_X:
		case BPF_S_ALU_DIV_X:
		case BPF_S_ALU_AND_K:
		case BPF_S_ALU_AND_X:
		case BPF_S_ALU_OR_K:
		case BPF_S_ALU_OR_X:
		case BPF_S_ALU_XOR_K:
		case BPF_S_ALU_XOR_X:
		case BPF_S_ALU_LSH_K:
		case BPF_S_ALU_LSH_X:
		case BPF_S_ALU_RSH_K:
		case BPF_S_ALU_RSH_X:
		case BPF_S_ALU_NEG:
		case BPF_S_LD_IMM:
		case BPF_S_LDX_IMM:
		case BPF_S_MISC_TAX:
		case BPF_S_MISC_TXA:
		case BPF_S_ALU_DIV_K:
		case BPF_S_LD_MEM:
		case BPF_S_LDX_MEM:
		case BPF_S_ST:
		case BPF_S_STX:
		case BPF_S_JMP_JA:
		case BPF_S_JMP_JEQ_K:
		case BPF_S_JMP_JEQ_X:
		case BPF_S_JMP_JGE_K:
		case BPF_S_JMP_JGE_X:
		case BPF_S_JMP_JGT_K:
		case BPF_S_JMP_JGT_X:
		case BPF_S_JMP_JSET_K:
		case BPF_S_JMP_JSET_X:
			continue;
		default:
			return -EINVAL;
		}
	}
	return 0;
}

/**
 * seccomp_run_filters - evaluates all seccomp filters against @syscall
 * @syscall: number of the current system call
 *
 * Returns valid seccomp BPF response codes.
 */
static u32 seccomp_run_filters(int syscall)
{
	struct seccomp_filter *f;
	u32 ret = SECCOMP_RET_ALLOW;

	/* Ensure unexpected behavior doesn't result in failing open. */
	if (WARN_ON(current->seccomp.filter == NULL))
		return SECCOMP_RET_KILL;

	/*
	 * All filters in the list are evaluated and the lowest BPF return
	 * value always takes priority (ignoring the DATA).
	 */
	for (f = current->seccomp.filter; f; f = f->prev) {
		u32 cur_ret = sk_run_filter(NULL, f->insns);
		if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
			ret = cur_ret;
	}
	return ret;
}

/**
 * seccomp_attach_filter: Attaches a seccomp filter to current.
 * @fprog: BPF program to install
 *
 * Returns 0 on success or an errno on failure.
 */
static long seccomp_attach_filter(struct sock_fprog *fprog)
{
	struct seccomp_filter *filter;
	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
	unsigned long total_insns = fprog->len;
	long ret;

	if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
		return -EINVAL;

	for (filter = current->seccomp.filter; filter; filter = filter->prev)
		total_insns += filter->len + 4;  /* include a 4 instr penalty */
	if (total_insns > MAX_INSNS_PER_PATH)
		return -ENOMEM;

	/*
	 * Installing a seccomp filter requires that the task have
	 * CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
	 * This avoids scenarios where unprivileged tasks can affect the
	 * behavior of privileged children.
	 */
	if (!current->no_new_privs &&
	    security_capable_noaudit(current_cred(), current_user_ns(),
				     CAP_SYS_ADMIN) != 0)
		return -EACCES;

	/* Allocate a new seccomp_filter */
	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size,
			 GFP_KERNEL|__GFP_NOWARN);
	if (!filter)
		return -ENOMEM;
	atomic_set(&filter->usage, 1);
	filter->len = fprog->len;

	/* Copy the instructions from fprog. */
	ret = -EFAULT;
	if (copy_from_user(filter->insns, fprog->filter, fp_size))
		goto fail;

	/* Check and rewrite the fprog via the skb checker */
	ret = sk_chk_filter(filter->insns, filter->len);
	if (ret)
		goto fail;

	/* Check and rewrite the fprog for seccomp use */
	ret = seccomp_check_filter(filter->insns, filter->len);
	if (ret)
		goto fail;

	/*
	 * If there is an existing filter, make it the prev and don't drop its
	 * task reference.
	 */
	filter->prev = current->seccomp.filter;
	current->seccomp.filter = filter;
	return 0;
fail:
	kfree(filter);
	return ret;
}

/**
 * seccomp_attach_user_filter - attaches a user-supplied sock_fprog
 * @user_filter: pointer to the user data containing a sock_fprog.
 *
 * Returns 0 on success and non-zero otherwise.
 */
long seccomp_attach_user_filter(char __user *user_filter)
{
	struct sock_fprog fprog;
	long ret = -EFAULT;

#ifdef CONFIG_COMPAT
	if (is_compat_task()) {
		struct compat_sock_fprog fprog32;
		if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
			goto out;
		fprog.len = fprog32.len;
		fprog.filter = compat_ptr(fprog32.filter);
	} else /* falls through to the if below. */
#endif
	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
		goto out;
	ret = seccomp_attach_filter(&fprog);
out:
	return ret;
}

/* get_seccomp_filter - increments the reference count of the filter on @tsk */
void get_seccomp_filter(struct task_struct *tsk)
{
	struct seccomp_filter *orig = tsk->seccomp.filter;
	if (!orig)
		return;
	/* Reference count is bounded by the number of total processes. */
	atomic_inc(&orig->usage);
}

/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
void put_seccomp_filter(struct task_struct *tsk)
{
	struct seccomp_filter *orig = tsk->seccomp.filter;
	/* Clean up single-reference branches iteratively. */
	while (orig && atomic_dec_and_test(&orig->usage)) {
		struct seccomp_filter *freeme = orig;
		orig = orig->prev;
		kfree(freeme);
	}
}

/**
 * seccomp_send_sigsys - signals the task to allow in-process syscall emulation
 * @syscall: syscall number to send to userland
 * @reason: filter-supplied reason code to send to userland (via si_errno)
 *
 * Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
 */
static void seccomp_send_sigsys(int syscall, int reason)
{
	struct siginfo info;
	memset(&info, 0, sizeof(info));
	info.si_signo = SIGSYS;
	info.si_code = SYS_SECCOMP;
	info.si_call_addr = (void __user *)KSTK_EIP(current);
	info.si_errno = reason;
	info.si_arch = syscall_get_arch(current, task_pt_regs(current));
	info.si_syscall = syscall;
	force_sig_info(SIGSYS, &info, current);
}
#endif	/* CONFIG_SECCOMP_FILTER */

/*
 * Secure computing mode 1 allows only read/write/exit/sigreturn.
 * To be fully secure this must be combined with rlimit
 * to limit the stack allocations too.
 */
static int mode1_syscalls[] = {
	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
	0, /* null terminated */
};

#ifdef CONFIG_COMPAT
static int mode1_syscalls_32[] = {
	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
	0, /* null terminated */
};
#endif

int __secure_computing(int this_syscall)
{
	int mode = current->seccomp.mode;
	int exit_sig = 0;
	int *syscall;
	u32 ret;

	switch (mode) {
	case SECCOMP_MODE_STRICT:
		syscall = mode1_syscalls;
#ifdef CONFIG_COMPAT
		if (is_compat_task())
			syscall = mode1_syscalls_32;
#endif
		do {
			if (*syscall == this_syscall)
				return 0;
		} while (*++syscall);
		exit_sig = SIGKILL;
		ret = SECCOMP_RET_KILL;
		break;
#ifdef CONFIG_SECCOMP_FILTER
	case SECCOMP_MODE_FILTER: {
		int data;
		struct pt_regs *regs = task_pt_regs(current);
		ret = seccomp_run_filters(this_syscall);
		data = ret & SECCOMP_RET_DATA;
		ret &= SECCOMP_RET_ACTION;
		switch (ret) {
		case SECCOMP_RET_ERRNO:
			/* Set the low-order 16-bits as a errno. */
			syscall_set_return_value(current, regs,
						 -data, 0);
			goto skip;
		case SECCOMP_RET_TRAP:
			/* Show the handler the original registers. */
			syscall_rollback(current, regs);
			/* Let the filter pass back 16 bits of data. */
			seccomp_send_sigsys(this_syscall, data);
			goto skip;
		case SECCOMP_RET_TRACE:
			/* Skip these calls if there is no tracer. */
			if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
				syscall_set_return_value(current, regs,
							 -ENOSYS, 0);
				goto skip;
			}
			/* Allow the BPF to provide the event message */
			ptrace_event(PTRACE_EVENT_SECCOMP, data);
			/*
			 * The delivery of a fatal signal during event
			 * notification may silently skip tracer notification.
			 * Terminating the task now avoids executing a system
			 * call that may not be intended.
			 */
			if (fatal_signal_pending(current))
				break;
			if (syscall_get_nr(current, regs) < 0)
				goto skip;  /* Explicit request to skip. */

			return 0;
		case SECCOMP_RET_ALLOW:
			return 0;
		case SECCOMP_RET_KILL:
		default:
			break;
		}
		exit_sig = SIGSYS;
		break;
	}
#endif
	default:
		BUG();
	}

#ifdef SECCOMP_DEBUG
	dump_stack();
#endif
	audit_seccomp(this_syscall, exit_sig, ret);
	do_exit(exit_sig);
#ifdef CONFIG_SECCOMP_FILTER
skip:
	audit_seccomp(this_syscall, exit_sig, ret);
#endif
	return -1;
}

long prctl_get_seccomp(void)
{
	return current->seccomp.mode;
}

/**
 * prctl_set_seccomp: configures current->seccomp.mode
 * @seccomp_mode: requested mode to use
 * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
 *
 * This function may be called repeatedly with a @seccomp_mode of
 * SECCOMP_MODE_FILTER to install additional filters.  Every filter
 * successfully installed will be evaluated (in reverse order) for each system
 * call the task makes.
 *
 * Once current->seccomp.mode is non-zero, it may not be changed.
 *
 * Returns 0 on success or -EINVAL on failure.
 */
long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
{
	long ret = -EINVAL;

	if (current->seccomp.mode &&
	    current->seccomp.mode != seccomp_mode)
		goto out;

	switch (seccomp_mode) {
	case SECCOMP_MODE_STRICT:
		ret = 0;
#ifdef TIF_NOTSC
		disable_TSC();
#endif
		break;
#ifdef CONFIG_SECCOMP_FILTER
	case SECCOMP_MODE_FILTER:
		ret = seccomp_attach_user_filter(filter);
		if (ret)
			goto out;
		break;
#endif
	default:
		goto out;
	}

	current->seccomp.mode = seccomp_mode;
	set_thread_flag(TIF_SECCOMP);
out:
	return ret;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/kernel/seccomp.c
	3	*
	4	* Copyright 2004-2005 Andrea Arcangeli <andrea@cpushare.com>
	5	*
e2cfabdf WD	6	* Copyright (C) 2012 Google, Inc.
	7	* Will Drewry <wad@chromium.org>
	8	*
	9	* This defines a simple but solid secure-computing facility.
	10	*
	11	* Mode 1 uses a fixed list of allowed system calls.
	12	* Mode 2 allows user-defined system call filters in the form
	13	* of Berkeley Packet Filters/Linux Socket Filters.
1da177e4 LT	14	*/
1da177e4 LT	15
e2cfabdf	16	#include <linux/atomic.h>
85e7bac3	17	#include <linux/audit.h>
5b101740	18	#include <linux/compat.h>
e2cfabdf WD	19	#include <linux/sched.h>
e2cfabdf WD	20	#include <linux/seccomp.h>
1da177e4 LT	21
1da177e4 LT	22	/* #define SECCOMP_DEBUG 1 */
e2cfabdf WD	23
	24	#ifdef CONFIG_SECCOMP_FILTER
	25	#include <asm/syscall.h>
	26	#include <linux/filter.h>
fb0fadf9	27	#include <linux/ptrace.h>
e2cfabdf WD	28	#include <linux/security.h>
	29	#include <linux/slab.h>
	30	#include <linux/tracehook.h>
	31	#include <linux/uaccess.h>
	32
	33	/**
	34	* struct seccomp_filter - container for seccomp BPF programs
	35	*
	36	* @usage: reference count to manage the object lifetime.
	37	* get/put helpers should be used when accessing an instance
	38	* outside of a lifetime-guarded section. In general, this
	39	* is only needed for handling filters shared across tasks.
	40	* @prev: points to a previously installed, or inherited, filter
	41	* @len: the number of instructions in the program
	42	* @insns: the BPF program instructions to evaluate
	43	*
	44	* seccomp_filter objects are organized in a tree linked via the @prev
	45	* pointer. For any task, it appears to be a singly-linked list starting
	46	* with current->seccomp.filter, the most recently attached or inherited filter.
	47	* However, multiple filters may share a @prev node, by way of fork(), which
	48	* results in a unidirectional tree existing in memory. This is similar to
	49	* how namespaces work.
	50	*
	51	* seccomp_filter objects should never be modified after being attached
	52	* to a task_struct (other than @usage).
	53	*/
	54	struct seccomp_filter {
	55	atomic_t usage;
	56	struct seccomp_filter *prev;
	57	unsigned short len; /* Instruction count */
	58	struct sock_filter insns[];
	59	};
	60
	61	/* Limit any path through the tree to 256KB worth of instructions. */
	62	#define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter))
	63
e2cfabdf WD	64	/**
	65	* get_u32 - returns a u32 offset into data
	66	* @data: a unsigned 64 bit value
	67	* @index: 0 or 1 to return the first or second 32-bits
	68	*
	69	* This inline exists to hide the length of unsigned long. If a 32-bit
	70	* unsigned long is passed in, it will be extended and the top 32-bits will be
	71	* 0. If it is a 64-bit unsigned long, then whatever data is resident will be
	72	* properly returned.
	73	*
	74	* Endianness is explicitly ignored and left for BPF program authors to manage
	75	* as per the specific architecture.
	76	*/
	77	static inline u32 get_u32(u64 data, int index)
	78	{
	79	return ((u32 *)&data)[index];
	80	}
	81
	82	/* Helper for bpf_load below. */
	83	#define BPF_DATA(_name) offsetof(struct seccomp_data, _name)
	84	/**
	85	* bpf_load: checks and returns a pointer to the requested offset
	86	* @off: offset into struct seccomp_data to load from
	87	*
	88	* Returns the requested 32-bits of data.
	89	* seccomp_check_filter() should assure that @off is 32-bit aligned
	90	* and not out of bounds. Failure to do so is a BUG.
	91	*/
	92	u32 seccomp_bpf_load(int off)
	93	{
	94	struct pt_regs *regs = task_pt_regs(current);
	95	if (off == BPF_DATA(nr))
	96	return syscall_get_nr(current, regs);
	97	if (off == BPF_DATA(arch))
	98	return syscall_get_arch(current, regs);
	99	if (off >= BPF_DATA(args[0]) && off < BPF_DATA(args[6])) {
	100	unsigned long value;
	101	int arg = (off - BPF_DATA(args[0])) / sizeof(u64);
	102	int index = !!(off % sizeof(u64));
	103	syscall_get_arguments(current, regs, arg, 1, &value);
	104	return get_u32(value, index);
	105	}
	106	if (off == BPF_DATA(instruction_pointer))
	107	return get_u32(KSTK_EIP(current), 0);
	108	if (off == BPF_DATA(instruction_pointer) + sizeof(u32))
	109	return get_u32(KSTK_EIP(current), 1);
	110	/* seccomp_check_filter should make this impossible. */
	111	BUG();
	112	}
	113
	114	/**
	115	* seccomp_check_filter - verify seccomp filter code
	116	* @filter: filter to verify
	117	* @flen: length of filter
	118	*
	119	* Takes a previously checked filter (by sk_chk_filter) and
	120	* redirects all filter code that loads struct sk_buff data
	121	* and related data through seccomp_bpf_load. It also
	122	* enforces length and alignment checking of those loads.
	123	*
	124	* Returns 0 if the rule set is legal or -EINVAL if not.
	125	*/
	126	static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen)
	127	{
128	int pc;
129	for (pc = 0; pc < flen; pc++) {
130	struct sock_filter *ftest = &filter[pc];
131	u16 code = ftest->code;
132	u32 k = ftest->k;
133
134	switch (code) {
135	case BPF_S_LD_W_ABS:
136	ftest->code = BPF_S_ANC_SECCOMP_LD_W;
137	/* 32-bit aligned and not out of bounds. */
138	if (k >= sizeof(struct seccomp_data) \|\| k & 3)
139	return -EINVAL;
140	continue;
141	case BPF_S_LD_W_LEN:
142	ftest->code = BPF_S_LD_IMM;
143	ftest->k = sizeof(struct seccomp_data);
144	continue;
145	case BPF_S_LDX_W_LEN:
146	ftest->code = BPF_S_LDX_IMM;
147	ftest->k = sizeof(struct seccomp_data);
148	continue;
149	/* Explicitly include allowed calls. */
150	case BPF_S_RET_K:
151	case BPF_S_RET_A:
152	case BPF_S_ALU_ADD_K:
153	case BPF_S_ALU_ADD_X:
154	case BPF_S_ALU_SUB_K:
155	case BPF_S_ALU_SUB_X:
156	case BPF_S_ALU_MUL_K:
157	case BPF_S_ALU_MUL_X:
158	case BPF_S_ALU_DIV_X:
159	case BPF_S_ALU_AND_K:
160	case BPF_S_ALU_AND_X:
161	case BPF_S_ALU_OR_K:
162	case BPF_S_ALU_OR_X:
d1327479 NS	163	case BPF_S_ALU_XOR_K:
d1327479 NS	164	case BPF_S_ALU_XOR_X:
e2cfabdf WD	165	case BPF_S_ALU_LSH_K:
	166	case BPF_S_ALU_LSH_X:
	167	case BPF_S_ALU_RSH_K:
	168	case BPF_S_ALU_RSH_X:
	169	case BPF_S_ALU_NEG:
	170	case BPF_S_LD_IMM:
	171	case BPF_S_LDX_IMM:
	172	case BPF_S_MISC_TAX:
	173	case BPF_S_MISC_TXA:
	174	case BPF_S_ALU_DIV_K:
	175	case BPF_S_LD_MEM:
	176	case BPF_S_LDX_MEM:
	177	case BPF_S_ST:
	178	case BPF_S_STX:
	179	case BPF_S_JMP_JA:
	180	case BPF_S_JMP_JEQ_K:
	181	case BPF_S_JMP_JEQ_X:
	182	case BPF_S_JMP_JGE_K:
	183	case BPF_S_JMP_JGE_X:
	184	case BPF_S_JMP_JGT_K:
	185	case BPF_S_JMP_JGT_X:
	186	case BPF_S_JMP_JSET_K:
	187	case BPF_S_JMP_JSET_X:
	188	continue;
	189	default:
	190	return -EINVAL;
	191	}
	192	}
	193	return 0;
	194	}
	195
	196	/**
	197	* seccomp_run_filters - evaluates all seccomp filters against @syscall
	198	* @syscall: number of the current system call
	199	*
	200	* Returns valid seccomp BPF response codes.
	201	*/
	202	static u32 seccomp_run_filters(int syscall)
	203	{
	204	struct seccomp_filter *f;
acf3b2c7 WD	205	u32 ret = SECCOMP_RET_ALLOW;
	206
	207	/* Ensure unexpected behavior doesn't result in failing open. */
	208	if (WARN_ON(current->seccomp.filter == NULL))
	209	return SECCOMP_RET_KILL;
	210
e2cfabdf WD	211	/*
e2cfabdf WD	212	* All filters in the list are evaluated and the lowest BPF return
acf3b2c7	213	* value always takes priority (ignoring the DATA).
e2cfabdf WD	214	*/
e2cfabdf WD	215	for (f = current->seccomp.filter; f; f = f->prev) {
acf3b2c7 WD	216	u32 cur_ret = sk_run_filter(NULL, f->insns);
	217	if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
	218	ret = cur_ret;
e2cfabdf WD	219	}
	220	return ret;
	221	}
	222
	223	/**
	224	* seccomp_attach_filter: Attaches a seccomp filter to current.
	225	* @fprog: BPF program to install
	226	*
	227	* Returns 0 on success or an errno on failure.
	228	*/
	229	static long seccomp_attach_filter(struct sock_fprog *fprog)
	230	{
	231	struct seccomp_filter *filter;
	232	unsigned long fp_size = fprog->len * sizeof(struct sock_filter);
	233	unsigned long total_insns = fprog->len;
	234	long ret;
	235
	236	if (fprog->len == 0 \|\| fprog->len > BPF_MAXINSNS)
	237	return -EINVAL;
	238
	239	for (filter = current->seccomp.filter; filter; filter = filter->prev)
	240	total_insns += filter->len + 4; /* include a 4 instr penalty */
	241	if (total_insns > MAX_INSNS_PER_PATH)
	242	return -ENOMEM;
	243
	244	/*
	245	* Installing a seccomp filter requires that the task have
	246	* CAP_SYS_ADMIN in its namespace or be running with no_new_privs.
	247	* This avoids scenarios where unprivileged tasks can affect the
	248	* behavior of privileged children.
	249	*/
	250	if (!current->no_new_privs &&
	251	security_capable_noaudit(current_cred(), current_user_ns(),
	252	CAP_SYS_ADMIN) != 0)
	253	return -EACCES;
	254
	255	/* Allocate a new seccomp_filter */
	256	filter = kzalloc(sizeof(struct seccomp_filter) + fp_size,
	257	GFP_KERNEL\|__GFP_NOWARN);
	258	if (!filter)
	259	return -ENOMEM;
	260	atomic_set(&filter->usage, 1);
	261	filter->len = fprog->len;
	262
	263	/* Copy the instructions from fprog. */
	264	ret = -EFAULT;
	265	if (copy_from_user(filter->insns, fprog->filter, fp_size))
	266	goto fail;
	267
	268	/* Check and rewrite the fprog via the skb checker */
	269	ret = sk_chk_filter(filter->insns, filter->len);
	270	if (ret)
	271	goto fail;
	272
	273	/* Check and rewrite the fprog for seccomp use */
	274	ret = seccomp_check_filter(filter->insns, filter->len);
	275	if (ret)
	276	goto fail;
	277
	278	/*
	279	* If there is an existing filter, make it the prev and don't drop its
	280	* task reference.
	281	*/
	282	filter->prev = current->seccomp.filter;
283	current->seccomp.filter = filter;
284	return 0;
285	fail:
286	kfree(filter);
287	return ret;
288	}
289
290	/**
291	* seccomp_attach_user_filter - attaches a user-supplied sock_fprog
292	* @user_filter: pointer to the user data containing a sock_fprog.
293	*
294	* Returns 0 on success and non-zero otherwise.
295	*/
296	long seccomp_attach_user_filter(char __user *user_filter)
297	{
298	struct sock_fprog fprog;
299	long ret = -EFAULT;
300
301	#ifdef CONFIG_COMPAT
302	if (is_compat_task()) {
303	struct compat_sock_fprog fprog32;
304	if (copy_from_user(&fprog32, user_filter, sizeof(fprog32)))
305	goto out;
306	fprog.len = fprog32.len;
307	fprog.filter = compat_ptr(fprog32.filter);
308	} else /* falls through to the if below. */
309	#endif
310	if (copy_from_user(&fprog, user_filter, sizeof(fprog)))
311	goto out;
312	ret = seccomp_attach_filter(&fprog);
313	out:
314	return ret;
315	}
316
317	/* get_seccomp_filter - increments the reference count of the filter on @tsk */
318	void get_seccomp_filter(struct task_struct *tsk)
319	{
320	struct seccomp_filter *orig = tsk->seccomp.filter;
321	if (!orig)
322	return;
323	/* Reference count is bounded by the number of total processes. */
324	atomic_inc(&orig->usage);
325	}
326
327	/* put_seccomp_filter - decrements the ref count of tsk->seccomp.filter */
328	void put_seccomp_filter(struct task_struct *tsk)
329	{
330	struct seccomp_filter *orig = tsk->seccomp.filter;
331	/* Clean up single-reference branches iteratively. */
332	while (orig && atomic_dec_and_test(&orig->usage)) {
333	struct seccomp_filter *freeme = orig;
334	orig = orig->prev;
335	kfree(freeme);
336	}
337	}
bb6ea430 WD	338
	339	/**
	340	* seccomp_send_sigsys - signals the task to allow in-process syscall emulation
	341	* @syscall: syscall number to send to userland
	342	* @reason: filter-supplied reason code to send to userland (via si_errno)
	343	*
	344	* Forces a SIGSYS with a code of SYS_SECCOMP and related sigsys info.
	345	*/
	346	static void seccomp_send_sigsys(int syscall, int reason)
	347	{
	348	struct siginfo info;
	349	memset(&info, 0, sizeof(info));
	350	info.si_signo = SIGSYS;
	351	info.si_code = SYS_SECCOMP;
	352	info.si_call_addr = (void __user *)KSTK_EIP(current);
	353	info.si_errno = reason;
	354	info.si_arch = syscall_get_arch(current, task_pt_regs(current));
	355	info.si_syscall = syscall;
	356	force_sig_info(SIGSYS, &info, current);
	357	}
e2cfabdf	358	#endif /* CONFIG_SECCOMP_FILTER */
1da177e4 LT	359
	360	/*
	361	* Secure computing mode 1 allows only read/write/exit/sigreturn.
	362	* To be fully secure this must be combined with rlimit
	363	* to limit the stack allocations too.
	364	*/
	365	static int mode1_syscalls[] = {
	366	__NR_seccomp_read, __NR_seccomp_write, __NR_seccomp_exit, __NR_seccomp_sigreturn,
	367	0, /* null terminated */
	368	};
	369
5b101740	370	#ifdef CONFIG_COMPAT
1da177e4 LT	371	static int mode1_syscalls_32[] = {
	372	__NR_seccomp_read_32, __NR_seccomp_write_32, __NR_seccomp_exit_32, __NR_seccomp_sigreturn_32,
	373	0, /* null terminated */
	374	};
	375	#endif
	376
acf3b2c7	377	int __secure_computing(int this_syscall)
1da177e4 LT	378	{
1da177e4 LT	379	int mode = current->seccomp.mode;
e2cfabdf WD	380	int exit_sig = 0;
e2cfabdf WD	381	int *syscall;
8156b451	382	u32 ret;
1da177e4 LT	383
1da177e4 LT	384	switch (mode) {
e2cfabdf	385	case SECCOMP_MODE_STRICT:
1da177e4	386	syscall = mode1_syscalls;
5b101740 RM	387	#ifdef CONFIG_COMPAT
5b101740 RM	388	if (is_compat_task())
1da177e4 LT	389	syscall = mode1_syscalls_32;
	390	#endif
	391	do {
	392	if (*syscall == this_syscall)
acf3b2c7	393	return 0;
1da177e4	394	} while (*++syscall);
e2cfabdf	395	exit_sig = SIGKILL;
8156b451	396	ret = SECCOMP_RET_KILL;
1da177e4	397	break;
e2cfabdf	398	#ifdef CONFIG_SECCOMP_FILTER
8156b451 WD	399	case SECCOMP_MODE_FILTER: {
8156b451 WD	400	int data;
87b526d3	401	struct pt_regs *regs = task_pt_regs(current);
acf3b2c7 WD	402	ret = seccomp_run_filters(this_syscall);
acf3b2c7 WD	403	data = ret & SECCOMP_RET_DATA;
8156b451 WD	404	ret &= SECCOMP_RET_ACTION;
8156b451 WD	405	switch (ret) {
acf3b2c7 WD	406	case SECCOMP_RET_ERRNO:
acf3b2c7 WD	407	/* Set the low-order 16-bits as a errno. */
87b526d3	408	syscall_set_return_value(current, regs,
acf3b2c7 WD	409	-data, 0);
acf3b2c7 WD	410	goto skip;
bb6ea430 WD	411	case SECCOMP_RET_TRAP:
bb6ea430 WD	412	/* Show the handler the original registers. */
87b526d3	413	syscall_rollback(current, regs);
bb6ea430 WD	414	/* Let the filter pass back 16 bits of data. */
	415	seccomp_send_sigsys(this_syscall, data);
	416	goto skip;
fb0fadf9 WD	417	case SECCOMP_RET_TRACE:
fb0fadf9 WD	418	/* Skip these calls if there is no tracer. */
87b526d3 AL	419	if (!ptrace_event_enabled(current, PTRACE_EVENT_SECCOMP)) {
	420	syscall_set_return_value(current, regs,
	421	-ENOSYS, 0);
fb0fadf9	422	goto skip;
87b526d3	423	}
fb0fadf9 WD	424	/* Allow the BPF to provide the event message */
	425	ptrace_event(PTRACE_EVENT_SECCOMP, data);
	426	/*
	427	* The delivery of a fatal signal during event
	428	* notification may silently skip tracer notification.
	429	* Terminating the task now avoids executing a system
	430	* call that may not be intended.
	431	*/
	432	if (fatal_signal_pending(current))
	433	break;
87b526d3 AL	434	if (syscall_get_nr(current, regs) < 0)
	435	goto skip; /* Explicit request to skip. */
	436
fb0fadf9	437	return 0;
acf3b2c7 WD	438	case SECCOMP_RET_ALLOW:
	439	return 0;
	440	case SECCOMP_RET_KILL:
	441	default:
	442	break;
	443	}
e2cfabdf WD	444	exit_sig = SIGSYS;
e2cfabdf WD	445	break;
8156b451	446	}
e2cfabdf	447	#endif
1da177e4 LT	448	default:
	449	BUG();
	450	}
	451
	452	#ifdef SECCOMP_DEBUG
	453	dump_stack();
	454	#endif
acf3b2c7	455	audit_seccomp(this_syscall, exit_sig, ret);
e2cfabdf	456	do_exit(exit_sig);
8156b451	457	#ifdef CONFIG_SECCOMP_FILTER
acf3b2c7 WD	458	skip:
acf3b2c7 WD	459	audit_seccomp(this_syscall, exit_sig, ret);
8156b451	460	#endif
acf3b2c7	461	return -1;
1da177e4	462	}
1d9d02fe AA	463
	464	long prctl_get_seccomp(void)
	465	{
	466	return current->seccomp.mode;
	467	}
	468
e2cfabdf WD	469	/**
	470	* prctl_set_seccomp: configures current->seccomp.mode
	471	* @seccomp_mode: requested mode to use
	472	* @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
	473	*
	474	* This function may be called repeatedly with a @seccomp_mode of
	475	* SECCOMP_MODE_FILTER to install additional filters. Every filter
	476	* successfully installed will be evaluated (in reverse order) for each system
	477	* call the task makes.
	478	*
	479	* Once current->seccomp.mode is non-zero, it may not be changed.
	480	*
	481	* Returns 0 on success or -EINVAL on failure.
	482	*/
	483	long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
1d9d02fe	484	{
e2cfabdf	485	long ret = -EINVAL;
1d9d02fe	486
e2cfabdf WD	487	if (current->seccomp.mode &&
e2cfabdf WD	488	current->seccomp.mode != seccomp_mode)
1d9d02fe AA	489	goto out;
1d9d02fe AA	490
e2cfabdf WD	491	switch (seccomp_mode) {
	492	case SECCOMP_MODE_STRICT:
	493	ret = 0;
cf99abac AA	494	#ifdef TIF_NOTSC
	495	disable_TSC();
	496	#endif
e2cfabdf WD	497	break;
	498	#ifdef CONFIG_SECCOMP_FILTER
	499	case SECCOMP_MODE_FILTER:
	500	ret = seccomp_attach_user_filter(filter);
	501	if (ret)
	502	goto out;
	503	break;
	504	#endif
	505	default:
	506	goto out;
1d9d02fe AA	507	}
1d9d02fe AA	508
e2cfabdf WD	509	current->seccomp.mode = seccomp_mode;
	510	set_thread_flag(TIF_SECCOMP);
	511	out:
1d9d02fe AA	512	return ret;
1d9d02fe AA	513	}