The following commit has been merged into the core/entry branch of tip:
Commit-ID: 3f67987cdc09778e75098f9f5168832f8f8e1f1c
Gitweb: https://git.kernel.org/tip/3f67987cdc09778e75098f9f5168832f8f8e1f1c
Author: Gregory Price <gourry.memverge@xxxxxxxxx>
AuthorDate: Fri, 07 Apr 2023 13:18:33 -04:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Sun, 16 Apr 2023 14:23:07 +02:00
ptrace: Provide set/get interface for syscall user dispatch
The syscall user dispatch configuration can only be set by the task itself,
but lacks a ptrace set/get interface which makes it impossible to implement
checkpoint/restore for it.
Add the required ptrace requests and the get/set functions in the syscall
user dispatch code to make that possible.
Signed-off-by: Gregory Price <gregory.price@xxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230407171834.3558-4-gregory.price@xxxxxxxxxxxx
---
Documentation/admin-guide/syscall-user-dispatch.rst | 4 +-
include/linux/syscall_user_dispatch.h | 18 +++++-
include/uapi/linux/ptrace.h | 30 +++++++++-
kernel/entry/syscall_user_dispatch.c | 40 ++++++++++++-
kernel/ptrace.c | 9 +++-
5 files changed, 101 insertions(+)
diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Documentation/admin-guide/syscall-user-dispatch.rst
index 6031495..e3cfffe 100644
--- a/Documentation/admin-guide/syscall-user-dispatch.rst
+++ b/Documentation/admin-guide/syscall-user-dispatch.rst
@@ -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
--------------
diff --git a/include/linux/syscall_user_dispatch.h b/include/linux/syscall_user_dispatch.h
index a0ae443..641ca88 100644
--- a/include/linux/syscall_user_dispatch.h
+++ b/include/linux/syscall_user_dispatch.h
@@ -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 */
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index 195ae64..72c038f 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.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.
diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c
index 7f2add4..5340c5a 100644
--- a/kernel/entry/syscall_user_dispatch.c
+++ b/kernel/entry/syscall_user_dispatch.c
@@ -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>
@@ -122,3 +123,42 @@ int set_syscall_user_dispatch(unsigned long mode, unsigned long offset,
{
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
+ 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);
+}
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 0786450..443057b 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -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;
}
|