SukiSU-Ultra/kernel/kernel_compat.c

#include <linux/version.h>
#include <linux/fs.h>
#include <linux/nsproxy.h>
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 10, 0)
#include <linux/sched/task.h>
#else
#include <linux/sched.h>
#endif
#include <linux/uaccess.h>
#include <linux/filter.h>
#include <linux/seccomp.h>
#include "klog.h" // IWYU pragma: keep
#include "kernel_compat.h"

#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) ||                           \
	defined(CONFIG_IS_HW_HISI) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
#include <linux/key.h>
#include <linux/errno.h>
#include <linux/cred.h>

extern int install_session_keyring_to_cred(struct cred *, struct key *);
struct key *init_session_keyring = NULL;
static inline int install_session_keyring(struct key *keyring)
{
	struct cred *new;
	int ret;

	new = prepare_creds();
	if (!new)
		return -ENOMEM;

	ret = install_session_keyring_to_cred(new, keyring);
	if (ret < 0) {
		abort_creds(new);
		return ret;
	}

	return commit_creds(new);
}
#endif

struct file *ksu_filp_open_compat(const char *filename, int flags, umode_t mode)
{
#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 10, 0) ||                           \
	defined(CONFIG_IS_HW_HISI) || defined(CONFIG_KSU_ALLOWLIST_WORKAROUND)
	if (init_session_keyring != NULL && !current_cred()->session_keyring &&
	    (current->flags & PF_WQ_WORKER)) {
		pr_info("installing init session keyring for older kernel\n");
		install_session_keyring(init_session_keyring);
	}
#endif
	return filp_open(filename, flags, mode);
}

ssize_t ksu_kernel_read_compat(struct file *p, void *buf, size_t count,
			       loff_t *pos)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 14, 0) ||                          \
	defined(KSU_OPTIONAL_KERNEL_READ)
	return kernel_read(p, buf, count, pos);
#else
	loff_t offset = pos ? *pos : 0;
	ssize_t result = kernel_read(p, offset, (char *)buf, count);
	if (pos && result > 0) {
		*pos = offset + result;
	}
	return result;
#endif
}

ssize_t ksu_kernel_write_compat(struct file *p, const void *buf, size_t count,
				loff_t *pos)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 14, 0) ||                          \
	defined(KSU_OPTIONAL_KERNEL_WRITE)
	return kernel_write(p, buf, count, pos);
#else
	loff_t offset = pos ? *pos : 0;
	ssize_t result = kernel_write(p, buf, count, offset);
	if (pos && result > 0) {
		*pos = offset + result;
	}
	return result;
#endif
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0) ||                           \
	defined(KSU_OPTIONAL_STRNCPY)
long ksu_strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
				   long count)
{
	return strncpy_from_user_nofault(dst, unsafe_addr, count);
}
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(5, 3, 0)
long ksu_strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
				   long count)
{
	return strncpy_from_unsafe_user(dst, unsafe_addr, count);
}
#else
// Copied from: https://elixir.bootlin.com/linux/v4.9.337/source/mm/maccess.c#L201
long ksu_strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
				   long count)
{
	mm_segment_t old_fs = get_fs();
	long ret;

	if (unlikely(count <= 0))
		return 0;

	set_fs(USER_DS);
	pagefault_disable();
	ret = strncpy_from_user(dst, unsafe_addr, count);
	pagefault_enable();
	set_fs(old_fs);

	if (ret >= count) {
		ret = count;
		dst[ret - 1] = '\0';
	} else if (ret > 0) {
		ret++;
	}

	return ret;
}
#endif

long ksu_strncpy_from_user_retry(char *dst, const void __user *unsafe_addr,
				 long count)
{
	long ret;

	ret = ksu_strncpy_from_user_nofault(dst, unsafe_addr, count);
	if (likely(ret >= 0))
		return ret;

	// we faulted! fallback to slow path
	if (unlikely(!ksu_access_ok(unsafe_addr, count))) {
#ifdef CONFIG_KSU_DEBUG
		pr_err("%s: faulted!\n", __func__);
#endif
		return -EFAULT;
	}

	// why we don't do like how strncpy_from_user_nofault?
	ret = strncpy_from_user(dst, unsafe_addr, count);

	if (ret >= count) {
		ret = count;
		dst[ret - 1] = '\0';
	} else if (likely(ret >= 0)) {
		ret++;
	}

	return ret;
}

long ksu_copy_from_user_nofault(void *dst, const void __user *src, size_t size)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 8, 0)
	return copy_from_user_nofault(dst, src, size);
#else
	// https://elixir.bootlin.com/linux/v5.8/source/mm/maccess.c#L205
	long ret = -EFAULT;
	mm_segment_t old_fs = get_fs();

	set_fs(USER_DS);
	// tweaked to use ksu_access_ok
	if (ksu_access_ok(src, size)) {
		pagefault_disable();
		ret = __copy_from_user_inatomic(dst, src, size);
		pagefault_enable();
	}
	set_fs(old_fs);

	if (ret)
		return -EFAULT;
	return 0;
#endif
}

#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 10, 0)

struct action_cache {
	DECLARE_BITMAP(allow_native, SECCOMP_ARCH_NATIVE_NR);
#ifdef SECCOMP_ARCH_COMPAT
	DECLARE_BITMAP(allow_compat, SECCOMP_ARCH_COMPAT_NR);
#endif
};

struct seccomp_filter {
	refcount_t refs;
	refcount_t users;
	bool log;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 1, 0)
	bool wait_killable_recv;
#endif
	struct action_cache cache;
	struct seccomp_filter *prev;
	struct bpf_prog *prog;
	struct notification *notif;
	struct mutex notify_lock;
	wait_queue_head_t wqh;
};

void ksu_seccomp_clear_cache(struct seccomp_filter *filter, int nr)
{
	if (!filter) {
		return;
	}

	if (nr >= 0 && nr < SECCOMP_ARCH_NATIVE_NR) {
		clear_bit(nr, filter->cache.allow_native);
	}

#ifdef SECCOMP_ARCH_COMPAT
	if (nr >= 0 && nr < SECCOMP_ARCH_COMPAT_NR) {
		clear_bit(nr, filter->cache.allow_compat);
	}
#endif
}

void ksu_seccomp_allow_cache(struct seccomp_filter *filter, int nr)
{
	if (!filter) {
		return;
	}

	if (nr >= 0 && nr < SECCOMP_ARCH_NATIVE_NR) {
		set_bit(nr, filter->cache.allow_native);
	}

#ifdef SECCOMP_ARCH_COMPAT
	if (nr >= 0 && nr < SECCOMP_ARCH_COMPAT_NR) {
		set_bit(nr, filter->cache.allow_compat);
	}
#endif
}

#endif