Extracts the common check/assign logic, and separates the two mode
setting paths to make things more readable with fewer #ifdefs within
function bodies.
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
kernel/seccomp.c | 124 +++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 85 insertions(+), 39 deletions(-)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 8ab0b7116ed8..1fb162e8b032 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -193,7 +193,29 @@ static u32 seccomp_run_filters(int syscall)
}
return ret;
}
+#endif /* CONFIG_SECCOMP_FILTER */
+static inline bool seccomp_check_mode(struct task_struct *task,
+ unsigned long seccomp_mode)
+{
+ BUG_ON(!spin_is_locked(&task->sighand->siglock));
+
+ if (task->seccomp.mode && task->seccomp.mode != seccomp_mode)
+ return false;
+
+ return true;
+}
+
+static inline void seccomp_assign_mode(struct task_struct *task,
+ unsigned long seccomp_mode)
+{
+ BUG_ON(!spin_is_locked(&task->sighand->siglock));
+
+ task->seccomp.mode = seccomp_mode;
+ set_tsk_thread_flag(task, TIF_SECCOMP);
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
/**
* seccomp_prepare_filter: Prepares a seccomp filter for use.
* @fprog: BPF program to install
@@ -500,69 +522,86 @@ long prctl_get_seccomp(void)
}
/**
- * seccomp_set_mode: internal function for setting seccomp mode
- * @seccomp_mode: requested mode to use
- * @filter: optional struct sock_fprog for use with SECCOMP_MODE_FILTER
+ * seccomp_set_mode_strict: internal function for setting strict seccomp
*
- * This function may be called repeatedly with a @seccomp_mode of
- * SECCOMP_MODE_FILTER to install additional filters. Every filter
- * successfully installed will be evaluated (in reverse order) for each system
- * call the task makes.
+ * Once current->seccomp.mode is non-zero, it may not be changed.
+ *
+ * Returns 0 on success or -EINVAL on failure.
+ */
+static long seccomp_set_mode_strict(void)
+{
+ const unsigned long seccomp_mode = SECCOMP_MODE_STRICT;
+ unsigned long irqflags;
+ int ret = -EINVAL;
+
+ if (unlikely(!lock_task_sighand(current, &irqflags)))
+ return -EINVAL;
+
+ if (!seccomp_check_mode(current, seccomp_mode))
+ goto out;
+
+#ifdef TIF_NOTSC
+ disable_TSC();
+#endif
+ seccomp_assign_mode(current, seccomp_mode);
+ ret = 0;
+
+out:
+ unlock_task_sighand(current, &irqflags);
+
+ return ret;
+}
+
+#ifdef CONFIG_SECCOMP_FILTER
+/**
+ * seccomp_set_mode_filter: internal function for setting seccomp filter
+ * @filter: struct sock_fprog containing filter
+ *
+ * This function may be called repeatedly to install additional filters.
+ * Every filter successfully installed will be evaluated (in reverse order)
+ * for each system call the task makes.
*
* Once current->seccomp.mode is non-zero, it may not be changed.
*
* Returns 0 on success or -EINVAL on failure.
*/
-static long seccomp_set_mode(unsigned long seccomp_mode, char __user *filter)
+static long seccomp_set_mode_filter(char __user *filter)
{
+ const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
struct seccomp_filter *prepared = NULL;
unsigned long irqflags;
long ret = -EINVAL;
-#ifdef CONFIG_SECCOMP_FILTER
- /* Prepare the new filter outside of the seccomp lock. */
- if (seccomp_mode == SECCOMP_MODE_FILTER) {
- prepared = seccomp_prepare_user_filter(filter);
- if (IS_ERR(prepared))
- return PTR_ERR(prepared);
- }
-#endif
+ /* Prepare the new filter outside of any locking. */
+ prepared = seccomp_prepare_user_filter(filter);
+ if (IS_ERR(prepared))
+ return PTR_ERR(prepared);
if (unlikely(!lock_task_sighand(current, &irqflags)))
goto out_free;
- if (current->seccomp.mode &&
- current->seccomp.mode != seccomp_mode)
+ if (!seccomp_check_mode(current, seccomp_mode))
goto out;
- switch (seccomp_mode) {
- case SECCOMP_MODE_STRICT:
- ret = 0;
-#ifdef TIF_NOTSC
- disable_TSC();
-#endif
- break;
-#ifdef CONFIG_SECCOMP_FILTER
- case SECCOMP_MODE_FILTER:
- ret = seccomp_attach_filter(prepared);
- if (ret)
- goto out;
- /* Do not free the successfully attached filter. */
- prepared = NULL;
- break;
-#endif
- default:
+ ret = seccomp_attach_filter(prepared);
+ if (ret)
goto out;
- }
+ /* Do not free the successfully attached filter. */
+ prepared = NULL;
- current->seccomp.mode = seccomp_mode;
- set_thread_flag(TIF_SECCOMP);
+ seccomp_assign_mode(current, seccomp_mode);
out:
unlock_task_sighand(current, &irqflags);
out_free:
seccomp_filter_free(prepared);
return ret;
}
+#else
+static inline long seccomp_set_mode_filter(char __user *filter)
+{
+ return -EINVAL;
+}
+#endif
/**
* prctl_set_seccomp: configures current->seccomp.mode
@@ -573,5 +612,12 @@ out_free:
*/
long prctl_set_seccomp(unsigned long seccomp_mode, char __user *filter)
{
- return seccomp_set_mode(seccomp_mode, filter);
+ switch (seccomp_mode) {
+ case SECCOMP_MODE_STRICT:
+ return seccomp_set_mode_strict();
+ case SECCOMP_MODE_FILTER:
+ return seccomp_set_mode_filter(filter);
+ default:
+ return -EINVAL;
+ }
}
--
1.7.9.5
--
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