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Subject[PATCH 09/11] jump label: jump_label_text_reserved() to reserve our jump points
Add a jump_label_text_reserved(void *start, void *end), so that other
pieces of code that want to modify kernel text, can first verify that
jump label has not reserved the instruction.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
---
arch/x86/kernel/kprobes.c | 3 +-
include/linux/jump_label.h | 6 +++
kernel/jump_label.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
kernel/kprobes.c | 3 +-
4 files changed, 93 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index f2f56c0..7a7343b 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -1202,7 +1202,8 @@ static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)
}
/* Check whether the address range is reserved */
if (ftrace_text_reserved(src, src + len - 1) ||
- alternatives_text_reserved(src, src + len - 1))
+ alternatives_text_reserved(src, src + len - 1) ||
+ jump_label_text_reserved(src, src + len - 1))
return -EBUSY;

return len;
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 7de278d..2464348 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -30,6 +30,7 @@ extern void arch_jump_label_transform(struct jump_entry *entry,
extern const u8 *arch_get_jump_label_nop(void);

extern void jump_label_update(const char *name, enum jump_label_type type);
+extern int jump_label_text_reserved(void *start, void *end);

extern void apply_jump_label_nops(struct module *mod);

@@ -64,6 +65,11 @@ static inline int apply_jump_label_nops(struct module *mod)
return 0;
}

+static inline int jump_label_text_reserved(void *start, void *end)
+{
+ return 0;
+}
+
#endif

#endif
diff --git a/kernel/jump_label.c b/kernel/jump_label.c
index 1db7a63..f44c792 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -182,6 +182,89 @@ void jump_label_update(const char *name, enum jump_label_type type)
mutex_unlock(&jump_label_mutex);
}

+static int addr_conflict(struct jump_entry *entry, void *start, void *end)
+{
+ if (entry->code <= (unsigned long)end &&
+ entry->code + IDEAL_NOP_SIZE_5 > (unsigned long)start)
+ return 1;
+
+ return 0;
+}
+
+#ifdef CONFIG_MODULES
+
+static int module_conflict(void *start, void *end)
+{
+ struct hlist_head *head;
+ struct hlist_node *node, *node_next, *module_node, *module_node_next;
+ struct jump_label_entry *e;
+ struct jump_label_module_entry *e_module;
+ struct jump_entry *iter;
+ int i, count;
+ int conflict = 0;
+
+ for (i = 0; i < JUMP_LABEL_TABLE_SIZE; i++) {
+ head = &jump_label_table[i];
+ hlist_for_each_entry_safe(e, node, node_next, head, hlist) {
+ hlist_for_each_entry_safe(e_module, module_node,
+ module_node_next,
+ &(e->modules), hlist) {
+ count = e_module->nr_entries;
+ iter = e_module->table;
+ while (count--) {
+ if (addr_conflict(iter, start, end)) {
+ conflict = 1;
+ goto out;
+ }
+ iter++;
+ }
+ }
+ }
+ }
+out:
+ return conflict;
+}
+
+#endif
+
+/***
+ * jump_label_text_reserved - check if addr range is reserved
+ * @start: start text addr
+ * @end: end text addr
+ *
+ * checks if the text addr located between @start and @end
+ * overlaps with any of the jump label patch addresses. Code
+ * that wants to modify kernel text should first verify that
+ * it does not overlap with any of the jump label addresses.
+ *
+ * returns 1 if there is an overlap, 0 otherwise
+ */
+int jump_label_text_reserved(void *start, void *end)
+{
+ struct jump_entry *iter;
+ struct jump_entry *iter_start = __start___jump_table;
+ struct jump_entry *iter_stop = __start___jump_table;
+ int conflict = 0;
+
+ mutex_lock(&jump_label_mutex);
+ iter = iter_start;
+ while (iter < iter_stop) {
+ if (addr_conflict(iter, start, end)) {
+ conflict = 1;
+ goto out;
+ }
+ iter++;
+ }
+
+ /* now check modules */
+#ifdef CONFIG_MODULES
+ conflict = module_conflict(start, end);
+#endif
+out:
+ mutex_unlock(&jump_label_mutex);
+ return conflict;
+}
+
static int init_jump_label(void)
{
int ret;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 0ed46f3..e866e04 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1141,7 +1141,8 @@ int __kprobes register_kprobe(struct kprobe *p)
preempt_disable();
if (!kernel_text_address((unsigned long) p->addr) ||
in_kprobes_functions((unsigned long) p->addr) ||
- ftrace_text_reserved(p->addr, p->addr)) {
+ ftrace_text_reserved(p->addr, p->addr) ||
+ jump_label_text_reserved(p->addr, p->addr)) {
preempt_enable();
return -EINVAL;
}
--
1.7.0.1


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