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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id qh16-20020a0562144c1000b005dd8b93457bsm3938206qvb.19.2023.03.28.09.48.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Mar 2023 09:48:48 -0700 (PDT) From: Gregory Price X-Google-Original-From: Gregory Price To: linux-kernel@vger.kernel.org Cc: linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, oleg@redhat.com, avagin@gmail.com, peterz@infradead.org, luto@kernel.org, krisman@collabora.com, tglx@linutronix.de, corbet@lwn.net, shuah@kernel.org, catalin.marinas@arm.com, arnd@arndb.de, will@kernel.org, mark.rutland@arm.com, tongtiangen@huawei.com, robin.murphy@arm.com, Gregory Price Subject: [PATCH v14 3/4] ptrace,syscall_user_dispatch: checkpoint/restore support for SUD Date: Tue, 28 Mar 2023 12:48:12 -0400 Message-Id: <20230328164811.2451-4-gregory.price@memverge.com> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230328164811.2451-1-gregory.price@memverge.com> References: <20230328164811.2451-1-gregory.price@memverge.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Implement ptrace getter/setter interface for syscall user dispatch. These prctl settings are presently write-only, making it impossible to implement transparent checkpoint/restore via software like CRIU. 'on_dispatch' field is not exposed because it is a kernel-internal only field that cannot be 'true' when returning to userland. Signed-off-by: Gregory Price Reviewed-by: Oleg Nesterov --- .../admin-guide/syscall-user-dispatch.rst | 4 ++ include/linux/syscall_user_dispatch.h | 18 ++++++++ include/uapi/linux/ptrace.h | 29 +++++++++++++ kernel/entry/syscall_user_dispatch.c | 42 +++++++++++++++++++ kernel/ptrace.c | 9 ++++ 5 files changed, 102 insertions(+) diff --git a/Documentation/admin-guide/syscall-user-dispatch.rst b/Documentation/admin-guide/syscall-user-dispatch.rst index 60314953c728..f7648c08297e 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 task's 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..1e77b02344c3 100644 --- a/include/uapi/linux/ptrace.h +++ b/include/uapi/linux/ptrace.h @@ -112,6 +112,35 @@ 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 SUD + * @mode: One of PR_SYS_DISPATCH_ON or PR_SYS_DISPATCH_OFF + * @selector: Tracee's 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 tracee. + * process. 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 SUD 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 a0624c3cda75..af49c44fdc67 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 @@ -113,3 +114,44 @@ 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) +{ + int rc; + struct ptrace_sud_config cfg; + + if (size != sizeof(cfg)) + return -EINVAL; + + if (copy_from_user(&cfg, data, sizeof(cfg))) + return -EFAULT; + + rc = task_set_syscall_user_dispatch(task, cfg.mode, cfg.offset, cfg.len, + (char __user *)(uintptr_t)cfg.selector); + return rc; +} diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 54482193e1ed..d99376532b56 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; } -- 2.39.1