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authorMasami Hiramatsu (Google) <mhiramat@kernel.org>2023-12-01 14:53:56 +0900
committerMasami Hiramatsu (Google) <mhiramat@kernel.org>2023-12-01 14:53:56 +0900
commita1461f1fd6cfdc4b8917c9d4a91e92605d1f28dc (patch)
treecaed8315567be58b912560043e4dde9fe3214940
parentd839a656d0f3caca9f96e9bf912fd394ac6a11bc (diff)
rethook: Use __rcu pointer for rethook::handler
Since the rethook::handler is an RCU-maganged pointer so that it will notice readers the rethook is stopped (unregistered) or not, it should be an __rcu pointer and use appropriate functions to be accessed. This will use appropriate memory barrier when accessing it. OTOH, rethook::data is never changed, so we don't need to check it in get_kretprobe(). NOTE: To avoid sparse warning, rethook::handler is defined by a raw function pointer type with __rcu instead of rethook_handler_t. Link: https://lore.kernel.org/all/170126066201.398836.837498688669005979.stgit@devnote2/ Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook") Cc: stable@vger.kernel.org Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202311241808.rv9ceuAh-lkp@intel.com/ Tested-by: JP Kobryn <inwardvessel@gmail.com> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
-rw-r--r--include/linux/kprobes.h6
-rw-r--r--include/linux/rethook.h7
-rw-r--r--kernel/trace/rethook.c23
3 files changed, 22 insertions, 14 deletions
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 64672bace560..0ff44d6633e3 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -197,10 +197,8 @@ extern int arch_trampoline_kprobe(struct kprobe *p);
#ifdef CONFIG_KRETPROBE_ON_RETHOOK
static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
{
- RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
- "Kretprobe is accessed from instance under preemptive context");
-
- return (struct kretprobe *)READ_ONCE(ri->node.rethook->data);
+ /* rethook::data is non-changed field, so that you can access it freely. */
+ return (struct kretprobe *)ri->node.rethook->data;
}
static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
{
diff --git a/include/linux/rethook.h b/include/linux/rethook.h
index ce69b2b7bc35..ba60962805f6 100644
--- a/include/linux/rethook.h
+++ b/include/linux/rethook.h
@@ -28,7 +28,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long,
*/
struct rethook {
void *data;
- rethook_handler_t handler;
+ /*
+ * To avoid sparse warnings, this uses a raw function pointer with
+ * __rcu, instead of rethook_handler_t. But this must be same as
+ * rethook_handler_t.
+ */
+ void (__rcu *handler) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
struct objpool_head pool;
struct rcu_head rcu;
};
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index 6fd7d4ecbbc6..fa03094e9e69 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -48,7 +48,7 @@ static void rethook_free_rcu(struct rcu_head *head)
*/
void rethook_stop(struct rethook *rh)
{
- WRITE_ONCE(rh->handler, NULL);
+ rcu_assign_pointer(rh->handler, NULL);
}
/**
@@ -63,7 +63,7 @@ void rethook_stop(struct rethook *rh)
*/
void rethook_free(struct rethook *rh)
{
- WRITE_ONCE(rh->handler, NULL);
+ rethook_stop(rh);
call_rcu(&rh->rcu, rethook_free_rcu);
}
@@ -82,6 +82,12 @@ static int rethook_fini_pool(struct objpool_head *head, void *context)
return 0;
}
+static inline rethook_handler_t rethook_get_handler(struct rethook *rh)
+{
+ return (rethook_handler_t)rcu_dereference_check(rh->handler,
+ rcu_read_lock_any_held());
+}
+
/**
* rethook_alloc() - Allocate struct rethook.
* @data: a data to pass the @handler when hooking the return.
@@ -107,7 +113,7 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler,
return ERR_PTR(-ENOMEM);
rh->data = data;
- rh->handler = handler;
+ rcu_assign_pointer(rh->handler, handler);
/* initialize the objpool for rethook nodes */
if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh,
@@ -135,9 +141,10 @@ static void free_rethook_node_rcu(struct rcu_head *head)
*/
void rethook_recycle(struct rethook_node *node)
{
- lockdep_assert_preemption_disabled();
+ rethook_handler_t handler;
- if (likely(READ_ONCE(node->rethook->handler)))
+ handler = rethook_get_handler(node->rethook);
+ if (likely(handler))
objpool_push(node, &node->rethook->pool);
else
call_rcu(&node->rcu, free_rethook_node_rcu);
@@ -153,9 +160,7 @@ NOKPROBE_SYMBOL(rethook_recycle);
*/
struct rethook_node *rethook_try_get(struct rethook *rh)
{
- rethook_handler_t handler = READ_ONCE(rh->handler);
-
- lockdep_assert_preemption_disabled();
+ rethook_handler_t handler = rethook_get_handler(rh);
/* Check whether @rh is going to be freed. */
if (unlikely(!handler))
@@ -300,7 +305,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
rhn = container_of(first, struct rethook_node, llist);
if (WARN_ON_ONCE(rhn->frame != frame))
break;
- handler = READ_ONCE(rhn->rethook->handler);
+ handler = rethook_get_handler(rhn->rethook);
if (handler)
handler(rhn, rhn->rethook->data,
correct_ret_addr, regs);