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-rw-r--r--kernel/exit.c72
1 files changed, 72 insertions, 0 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 908e7a33e..02360ec3b 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -62,12 +62,59 @@
#include <linux/random.h>
#include <linux/rcuwait.h>
#include <linux/compat.h>
+#include <linux/sysfs.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
#include <asm/pgtable.h>
#include <asm/mmu_context.h>
+/*
+ * The default value should be high enough to not crash a system that randomly
+ * crashes its kernel from time to time, but low enough to at least not permit
+ * overflowing 32-bit refcounts or the ldsem writer count.
+ */
+static unsigned int oops_limit = 10000;
+
+#ifdef CONFIG_SYSCTL
+static struct ctl_table kern_exit_table[] = {
+ {
+ .procname = "oops_limit",
+ .data = &oops_limit,
+ .maxlen = sizeof(oops_limit),
+ .mode = 0644,
+ .proc_handler = proc_douintvec,
+ },
+ { }
+};
+
+static __init int kernel_exit_sysctls_init(void)
+{
+ register_sysctl_init("kernel", kern_exit_table);
+ return 0;
+}
+late_initcall(kernel_exit_sysctls_init);
+#endif
+
+static atomic_t oops_count = ATOMIC_INIT(0);
+
+#ifdef CONFIG_SYSFS
+static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *page)
+{
+ return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
+}
+
+static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
+
+static __init int kernel_exit_sysfs_init(void)
+{
+ sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
+ return 0;
+}
+late_initcall(kernel_exit_sysfs_init);
+#endif
+
static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
@@ -922,6 +969,31 @@ void __noreturn do_exit(long code)
}
EXPORT_SYMBOL_GPL(do_exit);
+void __noreturn make_task_dead(int signr)
+{
+ /*
+ * Take the task off the cpu after something catastrophic has
+ * happened.
+ */
+ unsigned int limit;
+
+ /*
+ * Every time the system oopses, if the oops happens while a reference
+ * to an object was held, the reference leaks.
+ * If the oops doesn't also leak memory, repeated oopsing can cause
+ * reference counters to wrap around (if they're not using refcount_t).
+ * This means that repeated oopsing can make unexploitable-looking bugs
+ * exploitable through repeated oopsing.
+ * To make sure this can't happen, place an upper bound on how often the
+ * kernel may oops without panic().
+ */
+ limit = READ_ONCE(oops_limit);
+ if (atomic_inc_return(&oops_count) >= limit && limit)
+ panic("Oopsed too often (kernel.oops_limit is %d)", limit);
+
+ do_exit(signr);
+}
+
void complete_and_exit(struct completion *comp, long code)
{
if (comp)