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 56814448B85 for ; Wed, 16 Sep 2026 08:07:58 +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=1789546086; cv=none; b=Ceo8A4WK7E9m/3Ykm25VaPq1yxEB4B1mCyYTGvq9+Y+wJnXpmpd9NfAKkkrlKtxSfljKl3gz9+LuK7GYCpZcG37COdJPgfjljgHSN4gJzHY2vjzHSeNMOwe4j7VpIigMUE/31VOTelomdW++nyKuxMBYodR83OkyljzJr6LyES8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789546086; c=relaxed/simple; bh=oPEhpeOsvAd/wFZNKb0o76ilTbZYcxo1nGa0qMbgsOw=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=UjexFG0KUtR6N7VOsMDDGHrzq+WogxTWTuRG4aMcu8Bzd3ghOsPmT0f3BJHrjEbQfDzYLqrKxZRNMxTxhJ9sjC/HVV5DR5wpinY9nuQESLJPhtEgEbrwMnSCmmmlUCfhTz9m0Hp6Cq4UDw2WIangXg27gHouy1fRT10tvE0k0h8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=W01XUI04; 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="W01XUI04" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 768391F00899; Wed, 16 Sep 2026 08:07:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789546074; bh=vIJE9b1yIQvofVNGFuFPO48bghGk6accFRtmlyNdkAs=; h=Subject:To:Cc:From:Date; b=W01XUI04umALUAw8aksWFPetHiDicX+Mvzv78t5XMMifzloDWwnXRYzqLTfNfyfAM GHw7C0Vyg1XGSMqzRRawGcZ/v/IDsW5PrJHi+vW2QmdkKC2TURWDtdfAqrA/50aucO 5TbZe+XBFeG7wXksSQzy/dZJ6SaQfseZlz8cAnQI= Subject: FAILED: patch "[PATCH] configfs: pin the symlink target's dirent instead of chasing" failed to apply to 5.10-stable tree To: vasilisalmpanis@gmail.com,leitao@debian.org Cc: From: Date: Wed, 16 Sep 2026 09:05:45 +0100 Message-ID: <2026091645-grappling-craziness-559e@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x a7c1290eef60711c10289c056ad32ed1f2b47b12 # git commit -s git send-email --to '' --in-reply-to '2026091645-grappling-craziness-559e@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From a7c1290eef60711c10289c056ad32ed1f2b47b12 Mon Sep 17 00:00:00 2001 From: Vasileios Almpanis Date: Thu, 30 Jul 2026 11:30:24 +0200 Subject: [PATCH] configfs: pin the symlink target's dirent instead of chasing ->ci_dentry create_link() reads the target's configfs_dirent from item->ci_dentry->d_fsdata, relying on the item reference taken by get_target(). That reference pins the item, not its dentry: the dentry is pinned by DCACHE_PERSISTENT, which configfs_remove_dir() releases via simple_rmdir() while the item is still alive. A symlink racing with rmdir of its target can therefore find ->ci_dentry freed and its dirent released, triggering WARN_ON(!atomic_read(&sd->s_count)) in configfs_get(). Take the dirent in get_target() as well, under ->d_lock and atomically with the item reference, and pass it down to create_link(). A hashed dentry has not been killed yet, so its ->d_fsdata reference keeps the dirent alive there. Cc: stable@vger.kernel.org Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Signed-off-by: Vasileios Almpanis Tested-by: Breno Leitao Reviewed-by: Breno Leitao Link: https://patch.msgid.link/20260730093435.195441-2-vasilisalmpanis@gmail.com Signed-off-by: Breno Leitao diff --git a/fs/configfs/symlink.c b/fs/configfs/symlink.c index 31eb28b27309..3b31c714400f 100644 --- a/fs/configfs/symlink.c +++ b/fs/configfs/symlink.c @@ -76,9 +76,9 @@ static int configfs_get_target_path(struct config_item *item, static int create_link(struct config_item *parent_item, struct config_item *item, + struct configfs_dirent *target_sd, struct dentry *dentry) { - struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata; char *body; int ret; @@ -115,6 +115,7 @@ static int create_link(struct config_item *parent_item, static int get_target(const char *symname, struct config_item **target, + struct configfs_dirent **target_sd, struct super_block *sb) { struct path path __free(path_put) = {}; @@ -125,7 +126,20 @@ static int get_target(const char *symname, struct config_item **target, return ret; if (path.dentry->d_sb != sb) return -EPERM; - *target = configfs_get_config_item(path.dentry); + /* + * A hashed dentry guarantees that neither the item nor the dirent + * have been released yet, as removals unhash before dropping. + * Grab both references here. An item reference alone would not keep + * ->ci_dentry alive. + */ + spin_lock(&path.dentry->d_lock); + if (!d_unhashed(path.dentry)) { + struct configfs_dirent *sd = path.dentry->d_fsdata; + + *target = config_item_get(sd->s_element); + *target_sd = configfs_get(sd); + } + spin_unlock(&path.dentry->d_lock); if (!*target) return -ENOENT; return 0; @@ -139,6 +153,7 @@ int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir, struct configfs_dirent *sd; struct config_item *parent_item; struct config_item *target_item = NULL; + struct configfs_dirent *target_sd = NULL; const struct config_item_type *type; sd = dentry->d_parent->d_fsdata; @@ -182,7 +197,7 @@ int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir, * AV, a thoroughly annoyed bastard. */ inode_unlock(dir); - ret = get_target(symname, &target_item, dentry->d_sb); + ret = get_target(symname, &target_item, &target_sd, dentry->d_sb); inode_lock(dir); if (ret) goto out_put; @@ -196,13 +211,14 @@ int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir, ret = type->ct_item_ops->allow_link(parent_item, target_item); if (!ret) { mutex_lock(&configfs_symlink_mutex); - ret = create_link(parent_item, target_item, dentry); + ret = create_link(parent_item, target_item, target_sd, dentry); mutex_unlock(&configfs_symlink_mutex); if (ret && type->ct_item_ops->drop_link) type->ct_item_ops->drop_link(parent_item, target_item); } + configfs_put(target_sd); config_item_put(target_item); out_put: