From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5D03717DB for ; Wed, 6 Dec 2023 01:55:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z+4YMDzx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E109C433C7; Wed, 6 Dec 2023 01:55:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701827731; bh=XplUz52PVtPLqenCuiP070I9f3WGAbiIV7pE6xo4Ovc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Z+4YMDzxii/2PI81EAlllSy6zxjtyJmHmAY7sDJh8e5oQAbdldsViFCBMQEFXprob lCAw0mLvdTosdERK8AYAI5n2GUsPaw606fUgxq8EwBGe537vNQ9ZLnuTqPa7qvQJmn sZ5EvnHaZGer1AzG++x1bDNtLXdst4AuItQN3dxwgg+MBkSMlTTs9WEGetpr9j3SFT ldSF1QSgsSwfIs71UVS6elLVvFdBhkQbgkYaxinNo5I922+nOtqDs5tALFafrj/yp7 wDO4KD6nmH41ep1Ucw8as3p2sFBsvNflV9ekYu/rHgE1Ws7syKDY1e7/mtAKHfUV5T vOh0+JVpJfrxw== From: mhiramat@kernel.org To: stable@vger.kernel.org Cc: "Masami Hiramatsu (Google)" , kernel test robot , JP Kobryn Subject: [PATCH 6.1.y] rethook: Use __rcu pointer for rethook::handler Date: Wed, 6 Dec 2023 10:55:26 +0900 Message-ID: <20231206015526.39044-1-mhiramat@kernel.org> X-Mailer: git-send-email 2.43.0.rc2.451.g8631bc7472-goog In-Reply-To: <2023120321-emboss-bunion-bf59@gregkh> References: <2023120321-emboss-bunion-bf59@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Masami Hiramatsu (Google)" 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 Closes: https://lore.kernel.org/oe-kbuild-all/202311241808.rv9ceuAh-lkp@intel.com/ Tested-by: JP Kobryn Signed-off-by: Masami Hiramatsu (Google) (cherry picked from commit a1461f1fd6cfdc4b8917c9d4a91e92605d1f28dc) --- include/linux/kprobes.h | 6 ++---- include/linux/rethook.h | 7 ++++++- kernel/trace/rethook.c | 23 ++++++++++++++--------- 3 files changed, 22 insertions(+), 14 deletions(-) diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 85a64cb95d75..38a774287bde 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -202,10 +202,8 @@ 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 bdbe6717f45a..a00963f33bc1 100644 --- a/include/linux/rethook.h +++ b/include/linux/rethook.h @@ -29,7 +29,12 @@ typedef void (*rethook_handler_t) (struct rethook_node *, void *, struct pt_regs */ 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 *, struct pt_regs *); struct freelist_head pool; refcount_t ref; struct rcu_head rcu; diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index 468006cce7ca..3686626b52c5 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -63,7 +63,7 @@ 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); } /** @@ -78,11 +78,17 @@ 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); } +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. @@ -102,7 +108,7 @@ struct rethook *rethook_alloc(void *data, rethook_handler_t handler) } rh->data = data; - rh->handler = handler; + rcu_assign_pointer(rh->handler, handler); rh->pool.head = NULL; refcount_set(&rh->ref, 1); @@ -142,9 +148,10 @@ 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)) freelist_add(&node->freelist, &node->rethook->pool); else call_rcu(&node->rcu, free_rethook_node_rcu); @@ -160,11 +167,9 @@ NOKPROBE_SYMBOL(rethook_recycle); */ struct rethook_node *rethook_try_get(struct rethook *rh) { - rethook_handler_t handler = READ_ONCE(rh->handler); + rethook_handler_t handler = rethook_get_handler(rh); struct freelist_node *fn; - lockdep_assert_preemption_disabled(); - /* Check whether @rh is going to be freed. */ if (unlikely(!handler)) return NULL; @@ -312,7 +317,7 @@ 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, regs); -- 2.43.0.rc2.451.g8631bc7472-goog