Merge tag 'seccomp-next' of https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux into next-seccomp

add support for retrieving seccomp filter metadata (Tycho Andersen)

4 files changed, 94 insertions, 30 deletions

diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h
index 10f25f7e4304..c723a5c4e3ff 100644
--- 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 e3939e00980b..e46d82b91166 100644
--- 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 84b1367935e4..58291e9f3276 100644
--- 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 5f0dfb2abb8d..61bd9dc260c8 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -978,49 +978,68 @@ long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
 }
 
 #if defined(CONFIG_SECCOMP_FILTER) && defined(CONFIG_CHECKPOINT_RESTORE)
-long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
-                        void __user *data)
+static struct seccomp_filter *get_nth_filter(struct task_struct *task,
+                                             unsigned long filter_off)
 {
-        struct seccomp_filter *filter;
-        struct sock_fprog_kern *fprog;
-        long ret;
-        unsigned long count = 0;
-
-        if (!capable(CAP_SYS_ADMIN) ||
-            current->seccomp.mode != SECCOMP_MODE_DISABLED) {
-                return -EACCES;
-        }
+        struct seccomp_filter *orig, *filter;
+        unsigned long count;
 
+        /*
+         * Note: this is only correct because the caller should be the (ptrace)
+         * tracer of the task, otherwise lock_task_sighand is needed.
+         */
         spin_lock_irq(&task->sighand->siglock);
+
         if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
-                ret = -EINVAL;
-                goto out;
+                spin_unlock_irq(&task->sighand->siglock);
+                return ERR_PTR(-EINVAL);
         }
 
-        filter = task->seccomp.filter;
-        while (filter) {
-                filter = filter->prev;
+        orig = task->seccomp.filter;
+        __get_seccomp_filter(orig);
+        spin_unlock_irq(&task->sighand->siglock);
+
+        count = 0;
+        for (filter = orig; filter; filter = filter->prev)
                 count++;
-        }
 
         if (filter_off >= count) {
-                ret = -ENOENT;
+                filter = ERR_PTR(-ENOENT);
                 goto out;
         }
-        count -= filter_off;
 
-        filter = task->seccomp.filter;
-        while (filter && count > 1) {
-                filter = filter->prev;
+        count -= filter_off;
+        for (filter = orig; filter && count > 1; filter = filter->prev)
                 count--;
-        }
 
         if (WARN_ON(count != 1 || !filter)) {
-                /* The filter tree shouldn't shrink while we're using it. */
-                ret = -ENOENT;
+                filter = ERR_PTR(-ENOENT);
                 goto out;
         }
 
+        __get_seccomp_filter(filter);
+
+out:
+        __put_seccomp_filter(orig);
+        return filter;
+}
+
+long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
+                        void __user *data)
+{
+        struct seccomp_filter *filter;
+        struct sock_fprog_kern *fprog;
+        long ret;
+
+        if (!capable(CAP_SYS_ADMIN) ||
+            current->seccomp.mode != SECCOMP_MODE_DISABLED) {
+                return -EACCES;
+        }
+
+        filter = get_nth_filter(task, filter_off);
+        if (IS_ERR(filter))
+                return PTR_ERR(filter);
+
         fprog = filter->prog->orig_prog;
         if (!fprog) {
                 /* This must be a new non-cBPF filter, since we save
@@ -1035,17 +1054,44 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
         if (!data)
                 goto out;
 
-        __get_seccomp_filter(filter);
-        spin_unlock_irq(&task->sighand->siglock);
-
         if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog)))
                 ret = -EFAULT;
 
+out:
         __put_seccomp_filter(filter);
         return ret;
+}
 
-out:
-        spin_unlock_irq(&task->sighand->siglock);
+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