From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 96F24C4332F for ; Mon, 6 Nov 2023 23:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233580AbjKFXQQ (ORCPT ); Mon, 6 Nov 2023 18:16:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233586AbjKFXP4 (ORCPT ); Mon, 6 Nov 2023 18:15:56 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B99A1FC2; Mon, 6 Nov 2023 15:15:19 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0294C433CB; Mon, 6 Nov 2023 23:15:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1699312519; bh=Y5x5PN6koJMJwin07OwvGRNEt+WpRL1R7/y9Q1VCHhs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dn76nDhSQCwItZnp+q/4qI5+UkFeIg+3URTvdn1AKwWmkWIYC2jh/ljPT4d+1lMv3 d+S9dSygmmt9Xi1lOU91JwAWJGJ7DXEjJQvP+kyQgBv6xtF4PtFNXNUQHgExcoYg6B TRzS2WLW9HTymmjEAonxLciBMKPUHjQqUKmaaE97+sMKCgKiF69lCSY2ob49INd3y1 JsbXCQMzeOGeBv1kCz/RrL073ClsN0CPcf0LOEVwPlRo2qkVl+PYOKm49otIPGPtAu hL2C/R/04FSMyWRAV3GzvUQwcrAqfpjDcBkfDBgh8z6UNc720SbDL2zYPGh5fSdqZ9 Fz9WjKICACwaw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Zhen Lei , "Paul E . McKenney" , Frederic Weisbecker , Sasha Levin , quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, boqun.feng@gmail.com, jiangshanlai@gmail.com, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 6.5 02/13] rcu: Dump memory object info if callback function is invalid Date: Mon, 6 Nov 2023 18:14:55 -0500 Message-ID: <20231106231514.3735077-2-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106231514.3735077-1-sashal@kernel.org> References: <20231106231514.3735077-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.5.10 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Zhen Lei [ Upstream commit 2cbc482d325ee58001472c4359b311958c4efdd1 ] When a structure containing an RCU callback rhp is (incorrectly) freed and reallocated after rhp is passed to call_rcu(), it is not unusual for rhp->func to be set to NULL. This defeats the debugging prints used by __call_rcu_common() in kernels built with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y, which expect to identify the offending code using the identity of this function. And in kernels build without CONFIG_DEBUG_OBJECTS_RCU_HEAD=y, things are even worse, as can be seen from this splat: Unable to handle kernel NULL pointer dereference at virtual address 0 ... ... PC is at 0x0 LR is at rcu_do_batch+0x1c0/0x3b8 ... ... (rcu_do_batch) from (rcu_core+0x1d4/0x284) (rcu_core) from (__do_softirq+0x24c/0x344) (__do_softirq) from (__irq_exit_rcu+0x64/0x108) (__irq_exit_rcu) from (irq_exit+0x8/0x10) (irq_exit) from (__handle_domain_irq+0x74/0x9c) (__handle_domain_irq) from (gic_handle_irq+0x8c/0x98) (gic_handle_irq) from (__irq_svc+0x5c/0x94) (__irq_svc) from (arch_cpu_idle+0x20/0x3c) (arch_cpu_idle) from (default_idle_call+0x4c/0x78) (default_idle_call) from (do_idle+0xf8/0x150) (do_idle) from (cpu_startup_entry+0x18/0x20) (cpu_startup_entry) from (0xc01530) This commit therefore adds calls to mem_dump_obj(rhp) to output some information, for example: slab kmalloc-256 start ffff410c45019900 pointer offset 0 size 256 This provides the rough size of the memory block and the offset of the rcu_head structure, which as least provides at least a few clues to help locate the problem. If the problem is reproducible, additional slab debugging can be enabled, for example, CONFIG_DEBUG_SLAB=y, which can provide significantly more information. Signed-off-by: Zhen Lei Signed-off-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Signed-off-by: Sasha Levin --- kernel/rcu/rcu.h | 7 +++++++ kernel/rcu/srcutiny.c | 1 + kernel/rcu/srcutree.c | 1 + kernel/rcu/tasks.h | 1 + kernel/rcu/tiny.c | 1 + kernel/rcu/tree.c | 1 + 6 files changed, 12 insertions(+) diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 98c1544cf572b..7ae3496b0b58d 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -10,6 +10,7 @@ #ifndef __LINUX_RCU_H #define __LINUX_RCU_H +#include #include /* @@ -248,6 +249,12 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head) } #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ +static inline void debug_rcu_head_callback(struct rcu_head *rhp) +{ + if (unlikely(!rhp->func)) + kmem_dump_obj(rhp); +} + extern int rcu_cpu_stall_suppress_at_boot; static inline bool rcu_stall_is_suppressed_at_boot(void) diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 336af24e0fe35..c38e5933a5d69 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -138,6 +138,7 @@ void srcu_drive_gp(struct work_struct *wp) while (lh) { rhp = lh; lh = lh->next; + debug_rcu_head_callback(rhp); local_bh_disable(); rhp->func(rhp); local_bh_enable(); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 20d7a238d675a..b3e9bc3b60f0b 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1708,6 +1708,7 @@ static void srcu_invoke_callbacks(struct work_struct *work) rhp = rcu_cblist_dequeue(&ready_cbs); for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) { debug_rcu_head_unqueue(rhp); + debug_rcu_head_callback(rhp); local_bh_disable(); rhp->func(rhp); local_bh_enable(); diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index b770add3f8430..b64d45cdea9c4 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -493,6 +493,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); len = rcl.len; for (rhp = rcu_cblist_dequeue(&rcl); rhp; rhp = rcu_cblist_dequeue(&rcl)) { + debug_rcu_head_callback(rhp); local_bh_disable(); rhp->func(rhp); local_bh_enable(); diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 42f7589e51e09..fec804b790803 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -97,6 +97,7 @@ static inline bool rcu_reclaim_tiny(struct rcu_head *head) trace_rcu_invoke_callback("", head); f = head->func; + debug_rcu_head_callback(head); WRITE_ONCE(head->func, (rcu_callback_t)0L); f(head); rcu_lock_release(&rcu_callback_map); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 1449cb69a0e0e..9b9ebe6205b93 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2131,6 +2131,7 @@ static void rcu_do_batch(struct rcu_data *rdp) trace_rcu_invoke_callback(rcu_state.name, rhp); f = rhp->func; + debug_rcu_head_callback(rhp); WRITE_ONCE(rhp->func, (rcu_callback_t)0L); f(rhp); -- 2.42.0