From 3f67987cdc09778e75098f9f5168832f8f8e1f1c Mon Sep 17 00:00:00 2001 From: Gregory Price Date: Fri, 7 Apr 2023 13:18:33 -0400 Subject: [PATCH] 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 Signed-off-by: Thomas Gleixner Reviewed-by: Oleg Nesterov Link: https://lore.kernel.org/r/20230407171834.3558-4-gregory.price@memverge.com --- .../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 60314953c728..e3cfffef5a63 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 a0ae443fb7df..641ca8880995 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 195ae64a8c87..72c038fc71d0 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 7f2add43672d..5340c5aa89e7 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -4,6 +4,7 @@ */ #include #include +#include #include #include #include @@ -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 0786450074c1..443057bee87c 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -32,6 +32,7 @@ #include #include #include +#include #include /* 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; }