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-rw-r--r--kernel/entry/syscall_user_dispatch.c108
1 files changed, 108 insertions, 0 deletions
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
new file mode 100644
index 000000000..0b6379adf
--- /dev/null
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Collabora Ltd.
+ */
+#include <linux/sched.h>
+#include <linux/prctl.h>
+#include <linux/syscall_user_dispatch.h>
+#include <linux/uaccess.h>
+#include <linux/signal.h>
+#include <linux/elf.h>
+
+#include <linux/sched/signal.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/syscall.h>
+
+#include "common.h"
+
+static void trigger_sigsys(struct pt_regs *regs)
+{
+ struct kernel_siginfo info;
+
+ clear_siginfo(&info);
+ info.si_signo = SIGSYS;
+ info.si_code = SYS_USER_DISPATCH;
+ info.si_call_addr = (void __user *)KSTK_EIP(current);
+ info.si_errno = 0;
+ info.si_arch = syscall_get_arch(current);
+ info.si_syscall = syscall_get_nr(current, regs);
+
+ force_sig_info(&info);
+}
+
+bool syscall_user_dispatch(struct pt_regs *regs)
+{
+ struct syscall_user_dispatch *sd = &current->syscall_dispatch;
+ char state;
+
+ if (likely(instruction_pointer(regs) - sd->offset < sd->len))
+ return false;
+
+ if (unlikely(arch_syscall_is_vdso_sigreturn(regs)))
+ return false;
+
+ if (likely(sd->selector)) {
+ /*
+ * access_ok() is performed once, at prctl time, when
+ * the selector is loaded by userspace.
+ */
+ if (unlikely(__get_user(state, sd->selector))) {
+ force_exit_sig(SIGSEGV);
+ return true;
+ }
+
+ if (likely(state == SYSCALL_DISPATCH_FILTER_ALLOW))
+ return false;
+
+ if (state != SYSCALL_DISPATCH_FILTER_BLOCK) {
+ force_exit_sig(SIGSYS);
+ return true;
+ }
+ }
+
+ sd->on_dispatch = true;
+ syscall_rollback(current, regs);
+ trigger_sigsys(regs);
+
+ return true;
+}
+
+int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
+ unsigned long len, char __user *selector)
+{
+ switch (mode) {
+ case PR_SYS_DISPATCH_OFF:
+ if (offset || len || selector)
+ return -EINVAL;
+ break;
+ case PR_SYS_DISPATCH_ON:
+ /*
+ * Validate the direct dispatcher region just for basic
+ * sanity against overflow and a 0-sized dispatcher
+ * region. If the user is able to submit a syscall from
+ * an address, that address is obviously valid.
+ */
+ if (offset && offset + len <= offset)
+ return -EINVAL;
+
+ if (selector && !access_ok(selector, sizeof(*selector)))
+ return -EFAULT;
+
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ current->syscall_dispatch.selector = selector;
+ current->syscall_dispatch.offset = offset;
+ current->syscall_dispatch.len = len;
+ current->syscall_dispatch.on_dispatch = false;
+
+ if (mode == PR_SYS_DISPATCH_ON)
+ set_syscall_work(SYSCALL_USER_DISPATCH);
+ else
+ clear_syscall_work(SYSCALL_USER_DISPATCH);
+
+ return 0;
+}