From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 1AF78415F23; Tue, 21 Jul 2026 22:09:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784671742; cv=none; b=crVSZWhbaL+BeLAE5pueuvF931Co+3+QTAelM+LK2Zk9+BV8pgOebyBsHqws125YwVjlAq0d6atev1UEJnHScgFsgEL/dA10WKoU5tZsEAB74iy+nhbhH7vH+Rzq2xnDj+PIGmxOzMPO/qzyGlFU2gjYxizdt9MaB8PDW34Acig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784671742; c=relaxed/simple; bh=M9Rkh8afBQUg58kYMqkjlWjOGhdNL5974KyZ3/PTAYY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=epktvrWa0xyL4RUZyQc6Bc7dHP/qqVGwvD+s0caQtZqWK/rGW2nlL045Uc5jH0RqfgnUpuE8of7XXmB5jmLt3AyQWwETpMgrrUu45KoZTJniA0Wskwg13a9loFR+R3s1Kkse7xNB2c87+lda3o3NYuq6WiwajEpmj57ozlpTzk8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JQz8MDhA; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JQz8MDhA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A795D1F00A3A; Tue, 21 Jul 2026 22:09:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784671741; bh=cBTfq6Y1C65zR/6dj60oUqshsrERMPCp9FzsvP5iTQg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JQz8MDhAP/b60GrxI6WaImdR4qficky5CnvFH1m9XpnZDZqvabtVWfykR5gaT7HKz fHTlHfvTUsJXBubLPJspr4F82j8V/VxTu80jpq8wEbr3NYC6f0xQUSJj8HK8umE4m2 gI8vlVqJdNrSGJf8S82BQAK4Y91aeYSjzaLtFNjM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Al Viro , Sasha Levin Subject: [PATCH 5.15 318/843] configfs: fix lockless traversals of ->s_children Date: Tue, 21 Jul 2026 17:19:13 +0200 Message-ID: <20260721152413.174440435@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152405.946368001@linuxfoundation.org> References: <20260721152405.946368001@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro [ Upstream commit 9b9e8bb81c41fd27e7b57a1c936fde140548535f ] Having the parent directory locked protects entries from removal by another thread, but it does *not* protect cursors from being moved around by lseek() - or freed, for that matter. Fixes: 6f6107640625 ("configfs: Introduce configfs_dirent_lock") Reviewed-by: Jan Kara Signed-off-by: Al Viro Signed-off-by: Sasha Levin --- fs/configfs/dir.c | 54 +++++++++++++++++++++++++++++++++++------------ 1 file changed, 41 insertions(+), 13 deletions(-) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index afe2b802eb3193..01c9d54833b300 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -225,15 +225,16 @@ static int configfs_dirent_exists(struct configfs_dirent *parent_sd, { struct configfs_dirent * sd; + spin_lock(&configfs_dirent_lock); list_for_each_entry(sd, &parent_sd->s_children, s_sibling) { if (sd->s_element) { - const unsigned char *existing = configfs_get_name(sd); - if (strcmp(existing, new)) - continue; - else + if (strcmp(configfs_get_name(sd), new) == 0) { + spin_unlock(&configfs_dirent_lock); return -EEXIST; + } } } + spin_unlock(&configfs_dirent_lock); return 0; } @@ -551,11 +552,28 @@ static void configfs_detach_rollback(struct dentry *dentry) configfs_detach_rollback(sd->s_dentry); } +/* + * Find the next non-cursor. configfs_dirent_lock held by caller. + */ +static struct configfs_dirent *next_dirent(struct configfs_dirent *parent, + struct configfs_dirent *last) +{ + struct configfs_dirent *s; + + s = list_prepare_entry(last, &parent->s_children, s_sibling); + + list_for_each_entry_continue(s, &parent->s_children, s_sibling) { + if (s->s_element) + return s; + } + return NULL; +} + static void detach_attrs(struct config_item * item) { struct dentry * dentry = dget(item->ci_dentry); - struct configfs_dirent * parent_sd; - struct configfs_dirent * sd, * tmp; + struct configfs_dirent *parent_sd; + struct configfs_dirent *sd, *next; if (!dentry) return; @@ -564,15 +582,19 @@ static void detach_attrs(struct config_item * item) dentry->d_name.name); parent_sd = dentry->d_fsdata; - list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) { - if (!sd->s_element || !(sd->s_type & CONFIGFS_NOT_PINNED)) + + spin_lock(&configfs_dirent_lock); + for (sd = next_dirent(parent_sd, NULL); sd; sd = next) { + next = next_dirent(parent_sd, sd); + if (!(sd->s_type & CONFIGFS_NOT_PINNED)) continue; - spin_lock(&configfs_dirent_lock); list_del_init(&sd->s_sibling); spin_unlock(&configfs_dirent_lock); configfs_drop_dentry(sd, dentry); configfs_put(sd); + spin_lock(&configfs_dirent_lock); } + spin_unlock(&configfs_dirent_lock); /** * Drop reference from dget() on entrance. @@ -621,18 +643,20 @@ static void detach_groups(struct config_group *group) struct dentry * dentry = dget(group->cg_item.ci_dentry); struct dentry *child; struct configfs_dirent *parent_sd; - struct configfs_dirent *sd, *tmp; + struct configfs_dirent *sd, *next; if (!dentry) return; parent_sd = dentry->d_fsdata; - list_for_each_entry_safe(sd, tmp, &parent_sd->s_children, s_sibling) { - if (!sd->s_element || - !(sd->s_type & CONFIGFS_USET_DEFAULT)) + spin_lock(&configfs_dirent_lock); + for (sd = next_dirent(parent_sd, NULL); sd; sd = next) { + next = next_dirent(parent_sd, sd); + if (!(sd->s_type & CONFIGFS_USET_DEFAULT)) continue; child = sd->s_dentry; + spin_unlock(&configfs_dirent_lock); inode_lock(d_inode(child)); @@ -644,7 +668,9 @@ static void detach_groups(struct config_group *group) d_delete(child); dput(child); + spin_lock(&configfs_dirent_lock); } + spin_unlock(&configfs_dirent_lock); /** * Drop reference from dget() on entrance. @@ -1096,6 +1122,7 @@ configfs_find_subsys_dentry(struct configfs_dirent *root_sd, struct configfs_dirent *p; struct configfs_dirent *ret = NULL; + spin_lock(&configfs_dirent_lock); list_for_each_entry(p, &root_sd->s_children, s_sibling) { if (p->s_type & CONFIGFS_DIR && p->s_element == subsys_item) { @@ -1103,6 +1130,7 @@ configfs_find_subsys_dentry(struct configfs_dirent *root_sd, break; } } + spin_unlock(&configfs_dirent_lock); return ret; } -- 2.53.0