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Wed, 03 Jun 2026 09:22:25 -0700 (PDT) Received: from localhost ([2405:201:4027:a919:e2b2:8560:26ea:4d1]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2c164f85de1sm30328715ad.20.2026.06.03.09.22.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2026 09:22:25 -0700 (PDT) Date: Wed, 3 Jun 2026 21:52:23 +0530 From: Naveen Kumar Chaudhary To: mcgrof@kernel.org, petr.pavlu@suse.com, da.gomez@kernel.org, samitolvanen@google.com Cc: atomlin@atomlin.com, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] module: stats: add lockdep annotation for dup_failed_modules list traversal Message-ID: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" read_file_mod_stats() traverses dup_failed_modules with list_for_each_entry_rcu() while holding module_mutex, but does not pass the lockdep condition. This triggers a false-positive "RCU-list traversed in non-reader section" warning with CONFIG_PROVE_RCU_LIST=3Dy. The warning can be reproduced by: 1. Racing two loads of the same module to populate dup_failed_modules: insmod dummy.ko & insmod dummy.ko & 2. Reading the stats debugfs file: cat /sys/kernel/debug/modules/stats =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D WARNING: suspicious RCU usage 7.1.0-rc5-gae12a56ba16a #1 Not tainted ----------------------------- kernel/module/stats.c:385 RCU-list traversed in non-reader section!! other info that might help us debug this: rcu_scheduler_active =3D 2, debug_locks =3D 1 1 lock held by cat/128: #0: ffff80008288f7a8 (module_mutex){+.+.}-{4:4}, at: read_file_mod_stats+= 0x46c/0x5ec stack backtrace: CPU: 1 UID: 0 PID: 128 Comm: cat Kdump: loaded Not tainted 7.1.0-rc5-gae12= a56ba16a #1 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: show_stack+0x18/0x24 (C) __dump_stack+0x28/0x38 dump_stack_lvl+0x64/0x84 dump_stack+0x18/0x24 lockdep_rcu_suspicious+0x134/0x1d4 read_file_mod_stats+0x554/0x5ec full_proxy_read+0xe0/0x1ac vfs_read+0xd8/0x2b0 ksys_read+0x70/0xe4 __arm64_sys_read+0x1c/0x28 invoke_syscall+0x48/0xf8 el0_svc_common+0x8c/0xd8 do_el0_svc+0x1c/0x28 el0_svc+0x58/0x1d8 el0t_64_sync_handler+0x84/0x12c el0t_64_sync+0x198/0x19c The traversal is protected by module_mutex, so pass lockdep_is_held(&module_mutex) to inform the checker. Signed-off-by: Naveen Kumar Chaudhary --- kernel/module/stats.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/module/stats.c b/kernel/module/stats.c index 3a9672f93a8e..a62961acd8e3 100644 --- a/kernel/module/stats.c +++ b/kernel/module/stats.c @@ -382,7 +382,8 @@ static ssize_t read_file_mod_stats(struct file *file, c= har __user *user_buf, mutex_lock(&module_mutex); =20 =20 - list_for_each_entry_rcu(mod_fail, &dup_failed_modules, list) { + list_for_each_entry_rcu(mod_fail, &dup_failed_modules, list, + lockdep_is_held(&module_mutex)) { if (WARN_ON_ONCE(++count_failed >=3D MAX_FAILED_MOD_PRINT)) goto out_unlock; len +=3D scnprintf(buf + len, size - len, "%25s\t%15lu\t%25s\n", mod_fai= l->name, --=20 2.43.0