@@ -73,6 +73,10 @@ thread-wide, without the need to invoke the kernel directly. selector
can be set to SYSCALL_DISPATCH_FILTER_ALLOW or SYSCALL_DISPATCH_FILTER_BLOCK.
Any other value should terminate the program with a SIGSYS.
+Additionally, a tasks syscall user dispatch configuration can be peeked
+and poked via the PTRACE_(GET|SET)_SYSCALL_USER_DISPATCH_CONFIG ptrace
+requests. This is useful for checkpoint/restart software.
+
Security Notes
--------------
@@ -22,6 +22,12 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
#define clear_syscall_work_syscall_user_dispatch(tsk) \
clear_task_syscall_work(tsk, SYSCALL_USER_DISPATCH)
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+ void __user *data);
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+ void __user *data);
+
#else
struct syscall_user_dispatch {};
@@ -35,6 +41,18 @@ static inline void clear_syscall_work_syscall_user_dispatch(struct task_struct *
{
}
+static inline int syscall_user_dispatch_get_config(struct task_struct *task,
+ unsigned long size, void __user *data)
+{
+ return -EINVAL;
+}
+
+static inline int syscall_user_dispatch_set_config(struct task_struct *task,
+ unsigned long size, void __user *data)
+{
+ return -EINVAL;
+}
+
#endif /* CONFIG_GENERIC_ENTRY */
#endif /* _SYSCALL_USER_DISPATCH_H */
@@ -112,6 +112,36 @@ struct ptrace_rseq_configuration {
__u32 pad;
};
+#define PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG 0x4210
+#define PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG 0x4211
+
+/*
+ * struct ptrace_sud_config - Per-task configuration for Syscall User Dispatch
+ * @mode: One of PR_SYS_DISPATCH_ON or PR_SYS_DISPATCH_OFF
+ * @selector: Tracees user virtual address of SUD selector
+ * @offset: SUD exclusion area (virtual address)
+ * @len: Length of SUD exclusion area
+ *
+ * Used to get/set the syscall user dispatch configuration for a tracee.
+ * Selector is optional (may be NULL), and if invalid will produce
+ * a SIGSEGV in the tracee upon first access.
+ *
+ * If mode is PR_SYS_DISPATCH_ON, syscall dispatch will be enabled. If
+ * PR_SYS_DISPATCH_OFF, syscall dispatch will be disabled and all other
+ * parameters must be 0. The value in *selector (if not null), also determines
+ * whether syscall dispatch will occur.
+ *
+ * The Syscall User Dispatch Exclusion area described by offset/len is the
+ * virtual address space from which syscalls will not produce a user
+ * dispatch.
+ */
+struct ptrace_sud_config {
+ __u64 mode;
+ __u64 selector;
+ __u64 offset;
+ __u64 len;
+};
+
/*
* These values are stored in task->ptrace_message
* by ptrace_stop to describe the current syscall-stop.
@@ -4,6 +4,7 @@
*/
#include <linux/sched.h>
#include <linux/prctl.h>
+#include <linux/ptrace.h>
#include <linux/syscall_user_dispatch.h>
#include <linux/uaccess.h>
#include <linux/signal.h>
@@ -68,8 +69,9 @@ bool syscall_user_dispatch(struct pt_regs *regs)
return true;
}
-int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
- unsigned long len, char __user *selector)
+static int task_set_syscall_user_dispatch(struct task_struct *task, unsigned long mode,
+ unsigned long offset, unsigned long len,
+ char __user *selector)
{
switch (mode) {
case PR_SYS_DISPATCH_OFF:
@@ -86,7 +88,16 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
if (offset && offset + len <= offset)
return -EINVAL;
- if (selector && !access_ok(selector, sizeof(*selector)))
+ /*
+ * access_ok() will clear memory tags for tagged addresses
+ * if current has memory tagging enabled.
+
+ * To enable a tracer to set a tracees selector the
+ * selector address must be untagged for access_ok(),
+ * otherwise an untagged tracer will always fail to set a
+ * tagged tracees selector.
+ */
+ if (selector && !access_ok(untagged_addr(selector), sizeof(*selector)))
return -EFAULT;
break;
@@ -94,15 +105,60 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
return -EINVAL;
}
- current->syscall_dispatch.selector = selector;
- current->syscall_dispatch.offset = offset;
- current->syscall_dispatch.len = len;
- current->syscall_dispatch.on_dispatch = false;
+ task->syscall_dispatch.selector = selector;
+ task->syscall_dispatch.offset = offset;
+ task->syscall_dispatch.len = len;
+ task->syscall_dispatch.on_dispatch = false;
if (mode == PR_SYS_DISPATCH_ON)
- set_syscall_work(SYSCALL_USER_DISPATCH);
+ set_task_syscall_work(task, SYSCALL_USER_DISPATCH);
+ else
+ clear_task_syscall_work(task, SYSCALL_USER_DISPATCH);
+
+ return 0;
+}
+
+int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
+ unsigned long len, char __user *selector)
+{
+ return task_set_syscall_user_dispatch(current, mode, offset, len, selector);
+}
+
+int syscall_user_dispatch_get_config(struct task_struct *task, unsigned long size,
+ void __user *data)
+{
+ struct syscall_user_dispatch *sd = &task->syscall_dispatch;
+ struct ptrace_sud_config cfg;
+
+ if (size != sizeof(cfg))
+ return -EINVAL;
+
+ if (test_task_syscall_work(task, SYSCALL_USER_DISPATCH))
+ cfg.mode = PR_SYS_DISPATCH_ON;
else
- clear_syscall_work(SYSCALL_USER_DISPATCH);
+ cfg.mode = PR_SYS_DISPATCH_OFF;
+
+ cfg.offset = sd->offset;
+ cfg.len = sd->len;
+ cfg.selector = (__u64)(uintptr_t)sd->selector;
+
+ if (copy_to_user(data, &cfg, sizeof(cfg)))
+ return -EFAULT;
return 0;
}
+
+int syscall_user_dispatch_set_config(struct task_struct *task, unsigned long size,
+ void __user *data)
+{
+ struct ptrace_sud_config cfg;
+
+ if (size != sizeof(cfg))
+ return -EINVAL;
+
+ if (copy_from_user(&cfg, data, sizeof(cfg)))
+ return -EFAULT;
+
+ return task_set_syscall_user_dispatch(task, cfg.mode, cfg.offset, cfg.len,
+ (char __user *)(uintptr_t)cfg.selector);
+}
@@ -32,6 +32,7 @@
#include <linux/compat.h>
#include <linux/sched/signal.h>
#include <linux/minmax.h>
+#include <linux/syscall_user_dispatch.h>
#include <asm/syscall.h> /* for syscall_get_* */
@@ -1259,6 +1260,14 @@ int ptrace_request(struct task_struct *child, long request,
break;
#endif
+ case PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG:
+ ret = syscall_user_dispatch_set_config(child, addr, datavp);
+ break;
+
+ case PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG:
+ ret = syscall_user_dispatch_get_config(child, addr, datavp);
+ break;
+
default:
break;
}
@@ -1,4 +1,5 @@
# SPDX-License-Identifier: GPL-2.0-only
get_syscall_info
+get_set_sud
peeksiginfo
vmaccess
@@ -1,6 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
CFLAGS += -std=c99 -pthread -Wall $(KHDR_INCLUDES)
-TEST_GEN_PROGS := get_syscall_info peeksiginfo vmaccess
+TEST_GEN_PROGS := get_syscall_info peeksiginfo vmaccess get_set_sud
include ../lib.mk
new file mode 100644
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE
+#include "../kselftest_harness.h"
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <sys/syscall.h>
+#include <sys/prctl.h>
+
+#include "linux/ptrace.h"
+
+static int sys_ptrace(int request, pid_t pid, void *addr, void *data)
+{
+ return syscall(SYS_ptrace, request, pid, addr, data);
+}
+
+TEST(get_set_sud)
+{
+ struct ptrace_sud_config config;
+ pid_t child;
+ int ret = 0;
+ int status;
+
+ child = fork();
+ ASSERT_GE(child, 0);
+ if (child == 0) {
+ ASSERT_EQ(0, sys_ptrace(PTRACE_TRACEME, 0, 0, 0)) {
+ TH_LOG("PTRACE_TRACEME: %m");
+ }
+ kill(getpid(), SIGSTOP);
+ _exit(1);
+ }
+
+ waitpid(child, &status, 0);
+
+ memset(&config, 0xff, sizeof(config));
+ config.mode = PR_SYS_DISPATCH_ON;
+
+ ret = sys_ptrace(PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG, child,
+ (void *)sizeof(config), &config);
+
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(config.mode, PR_SYS_DISPATCH_OFF);
+ ASSERT_EQ(config.selector, 0);
+ ASSERT_EQ(config.offset, 0);
+ ASSERT_EQ(config.len, 0);
+
+ config.mode = PR_SYS_DISPATCH_ON;
+ config.selector = 0;
+ config.offset = 0x400000;
+ config.len = 0x1000;
+
+ ret = sys_ptrace(PTRACE_SET_SYSCALL_USER_DISPATCH_CONFIG, child,
+ (void *)sizeof(config), &config);
+
+ ASSERT_EQ(ret, 0);
+
+ memset(&config, 1, sizeof(config));
+ ret = sys_ptrace(PTRACE_GET_SYSCALL_USER_DISPATCH_CONFIG, child,
+ (void *)sizeof(config), &config);
+
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(config.mode, PR_SYS_DISPATCH_ON);
+ ASSERT_EQ(config.selector, 0);
+ ASSERT_EQ(config.offset, 0x400000);
+ ASSERT_EQ(config.len, 0x1000);
+
+ kill(child, SIGKILL);
+}
+
+TEST_HARNESS_MAIN