ptrace, seccomp: add support for retrieving seccomp metadata

With the new SECCOMP_FILTER_FLAG_LOG, we need to be able to extract these
flags for checkpoint restore, since they describe the state of a filter.

So, let's add PTRACE_SECCOMP_GET_METADATA, similar to ..._GET_FILTER, which
returns the metadata of the nth filter (right now, just the flags).
Hopefully this will be future proof, and new per-filter metadata can be
added to this struct.

Signed-off-by: Tycho Andersen <tycho@docker.com>
CC: Kees Cook <keescook@chromium.org>
CC: Andy Lutomirski <luto@amacapital.net>
CC: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 10f25f7e4304cc0330851a01ecd10353a4ad2ef6..c723a5c4e3ffdfc151fbf2e82c20a4c7ba7eeff7 100644 (file)
--- a/include/linux/seccomp.h
+++ b/include/linux/seccomp.h
@@ -95,11 +95,19 @@ static inline void get_seccomp_filter(struct task_struct *tsk)
 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
 extern long seccomp_get_filter(struct task_struct *task,
                               unsigned long filter_off, void __user *data);
+extern long seccomp_get_metadata(struct task_struct *task,
+                                unsigned long filter_off, void __user *data);
 #else
 static inline long seccomp_get_filter(struct task_struct *task,
                                      unsigned long n, void __user *data)
 {
        return -EINVAL;
 }
+static inline long seccomp_get_metadata(struct task_struct *task,
+                                       unsigned long filter_off,
+                                       void __user *data)
+{
+       return -EINVAL;
+}
 #endif /* CONFIG_SECCOMP_FILTER && CONFIG_CHECKPOINT_RESTORE */
 #endif /* _LINUX_SECCOMP_H */

diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index e3939e00980bb7976b0192a55581df2e8e005b15..e46d82b911669700662e5e4ec321b26db625f150 100644 (file)
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -66,6 +66,12 @@ struct ptrace_peeksiginfo_args {
 #define PTRACE_SETSIGMASK      0x420b
 
 #define PTRACE_SECCOMP_GET_FILTER      0x420c
+#define PTRACE_SECCOMP_GET_METADATA    0x420d
+
+struct seccomp_metadata {
+       unsigned long filter_off;       /* Input: which filter */
+       unsigned int flags;             /* Output: filter's flags */
+};
 
 /* Read signals from a shared (process wide) queue */
 #define PTRACE_PEEKSIGINFO_SHARED      (1 << 0)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 84b1367935e410f79770c06efadc20deb51346b3..58291e9f3276b23cff0f67e770f914cff02e9ba3 100644 (file)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -1092,6 +1092,10 @@ int ptrace_request(struct task_struct *child, long request,
                ret = seccomp_get_filter(child, addr, datavp);
                break;
 
+       case PTRACE_SECCOMP_GET_METADATA:
+               ret = seccomp_get_metadata(child, addr, datavp);
+               break;
+
        default:
                break;
        }

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 99bddaf790761988f5905a0d406aee286058c5f7..61bd9dc260c8ea6cc880e6f27bd552eb2e075586 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1061,6 +1061,39 @@ out:
        __put_seccomp_filter(filter);
        return ret;
 }
+
+long seccomp_get_metadata(struct task_struct *task,
+                         unsigned long size, void __user *data)
+{
+       long ret;
+       struct seccomp_filter *filter;
+       struct seccomp_metadata kmd = {};
+
+       if (!capable(CAP_SYS_ADMIN) ||
+           current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+               return -EACCES;
+       }
+
+       size = min_t(unsigned long, size, sizeof(kmd));
+
+       if (copy_from_user(&kmd, data, size))
+               return -EFAULT;
+
+       filter = get_nth_filter(task, kmd.filter_off);
+       if (IS_ERR(filter))
+               return PTR_ERR(filter);
+
+       memset(&kmd, 0, sizeof(kmd));
+       if (filter->log)
+               kmd.flags |= SECCOMP_FILTER_FLAG_LOG;
+
+       ret = size;
+       if (copy_to_user(data, &kmd, size))
+               ret = -EFAULT;
+
+       __put_seccomp_filter(filter);
+       return ret;
+}
 #endif
 
 #ifdef CONFIG_SYSCTL