From patchwork Fri Nov 24 16:25:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Johannes Berg X-Patchwork-Id: 13467943 X-Patchwork-Delegate: johannes@sipsolutions.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=sipsolutions.net header.i=@sipsolutions.net header.b="eplHiX6Z" Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:242:246e::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEB3D19A6; Fri, 24 Nov 2023 08:35:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Content-Type:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=eUQSivaM/C3sgIYV/55zPnV1kMbFsOGZiai+sGa+jDY=; t=1700843718; x=1702053318; b=eplHiX6ZMYIt11LKuIlWEPvXql5NNzBtK2Qbe3nAL30vIGt FwyzxUPM43QQVDRpK5rOtubghhSH5orccxvy4bO30sNFYVr3FRo6gEh+RLgXqF+JmygXOabWp9aji GtNi+yykJNzgnhM3ysbd7YOcVdz1ANXHQNTPxQ91C5s934QrL7SKN6ezcaq+T/73gIJIiFx8dVrZQ ylpxnbTXDUpkSTYbqrkecDjd/p5AHJmS2flrv6a69kcyLKkvahc1e0p4m3l4XkNrqr/YroUpi2nil D/+u1vUE0e2O0twKy7C3KVmyXzAx3/kLvucZN02tB1jDypmrLFajK/96of2N1YZA==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.97) (envelope-from ) id 1r6Z9A-00000002fA8-0Xch; Fri, 24 Nov 2023 17:35:16 +0100 From: Johannes Berg To: linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Johannes Berg Subject: [PATCH v2 2/6] debugfs: annotate debugfs handlers vs. removal with lockdep Date: Fri, 24 Nov 2023 17:25:25 +0100 Message-ID: <20231124172522.0442774abc66.Ia70a49792c448867fd61b0234e1da507b0f75086@changeid> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231124162522.16344-7-johannes@sipsolutions.net> References: <20231124162522.16344-7-johannes@sipsolutions.net> Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Johannes Berg When you take a lock in a debugfs handler but also try to remove the debugfs file under that lock, things can deadlock since the removal has to wait for all users to finish. Add lockdep annotations in debugfs_file_get()/_put() to catch such issues. Signed-off-by: Johannes Berg Acked-by: Greg Kroah-Hartman --- fs/debugfs/file.c | 10 ++++++++++ fs/debugfs/inode.c | 12 ++++++++++++ fs/debugfs/internal.h | 6 ++++++ 3 files changed, 28 insertions(+) diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c index e00189aebbf4..3eff92450fd5 100644 --- a/fs/debugfs/file.c +++ b/fs/debugfs/file.c @@ -108,6 +108,12 @@ int debugfs_file_get(struct dentry *dentry) kfree(fsd); fsd = READ_ONCE(dentry->d_fsdata); } +#ifdef CONFIG_LOCKDEP + fsd->lock_name = kasprintf(GFP_KERNEL, "debugfs:%pd", dentry); + lockdep_register_key(&fsd->key); + lockdep_init_map(&fsd->lockdep_map, fsd->lock_name ?: "debugfs", + &fsd->key, 0); +#endif } /* @@ -124,6 +130,8 @@ int debugfs_file_get(struct dentry *dentry) if (!refcount_inc_not_zero(&fsd->active_users)) return -EIO; + lock_map_acquire_read(&fsd->lockdep_map); + return 0; } EXPORT_SYMBOL_GPL(debugfs_file_get); @@ -141,6 +149,8 @@ void debugfs_file_put(struct dentry *dentry) { struct debugfs_fsdata *fsd = READ_ONCE(dentry->d_fsdata); + lock_map_release(&fsd->lockdep_map); + if (refcount_dec_and_test(&fsd->active_users)) complete(&fsd->active_users_drained); } diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index dcde4199a625..80f4f000dcc1 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -241,6 +241,14 @@ static void debugfs_release_dentry(struct dentry *dentry) if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT) return; + /* check it wasn't a dir (no fsdata) or automount (no real_fops) */ + if (fsd && fsd->real_fops) { +#ifdef CONFIG_LOCKDEP + lockdep_unregister_key(&fsd->key); + kfree(fsd->lock_name); +#endif + } + kfree(fsd); } @@ -744,6 +752,10 @@ static void __debugfs_file_removed(struct dentry *dentry) fsd = READ_ONCE(dentry->d_fsdata); if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT) return; + + lock_map_acquire(&fsd->lockdep_map); + lock_map_release(&fsd->lockdep_map); + if (!refcount_dec_and_test(&fsd->active_users)) wait_for_completion(&fsd->active_users_drained); } diff --git a/fs/debugfs/internal.h b/fs/debugfs/internal.h index f7c489b5a368..c7d61cfc97d2 100644 --- a/fs/debugfs/internal.h +++ b/fs/debugfs/internal.h @@ -7,6 +7,7 @@ #ifndef _DEBUGFS_INTERNAL_H_ #define _DEBUGFS_INTERNAL_H_ +#include struct file_operations; @@ -23,6 +24,11 @@ struct debugfs_fsdata { struct { refcount_t active_users; struct completion active_users_drained; +#ifdef CONFIG_LOCKDEP + struct lockdep_map lockdep_map; + struct lock_class_key key; + char *lock_name; +#endif }; }; };