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 ADD9A35EF1 for ; Mon, 4 Dec 2023 20:33:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="aFcbtPt2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B74E1C433C9; Mon, 4 Dec 2023 20:33:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1701722034; bh=qT22ZsEWOC48EvN1HHyJMi0wyTmmI5d9R9nP+L0thow=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aFcbtPt2zljluXLdHQYUWtZt9CR0MMxNI3nvpeJsozG3eQ3juSr/MRGk2fmIrQm7Z v5AO5ujWjJZKk3olxfoKb7K0LtyJQAsIXFT5otVfNoVsVUAF+9x+Rt1Z2SB7egWT16 rMOC8RW6unsR04Jy6uk0wbqdOsoSMmBhgbaBtAfIiROAvAefjEJdDSH4BIX0v/cLwq myUZ074aNHp4bneyV/5Jkd1iU0vNi+ws4/5loO3MxWg0EtmGHKuhaebi/wwbLhO40X FECt8JBuB0yJIYw/MnF50f4olOKYW9nhwxGUYLuaIIqxujKTluYcxObuStIZBwOuV6 RCWNmeGCQgf1Q== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Johannes Berg , Greg Kroah-Hartman , Sasha Levin Subject: [PATCH AUTOSEL 6.6 15/32] debugfs: annotate debugfs handlers vs. removal with lockdep Date: Mon, 4 Dec 2023 15:32:35 -0500 Message-ID: <20231204203317.2092321-15-sashal@kernel.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231204203317.2092321-1-sashal@kernel.org> References: <20231204203317.2092321-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.6.4 Content-Transfer-Encoding: 8bit From: Johannes Berg [ Upstream commit f4acfcd4deb158b96595250cc332901b282d15b0 ] 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. Acked-by: Greg Kroah-Hartman Signed-off-by: Johannes Berg Signed-off-by: Sasha Levin --- 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 e40229c47fe58..bd9e6284d0a82 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 dcde4199a625d..80f4f000dcc13 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 f7c489b5a368c..c7d61cfc97d26 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 }; }; }; -- 2.42.0