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 5B4CE4D0CD6 for ; Wed, 16 Sep 2026 16:47:39 +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=1789577275; cv=none; b=LTBdDrnv7kXI522sQdXfA8a8/htwZgmZ1YuKBz38ApXx8+mhTo6YpeeKxdLPr3OCWgTmBp1RLPOY24BvJ3enD3XBpmbOdWyxFF14ZkLNubHoB+UChqbP7wmaxcYKWaBvquGNzpFQW0oCCCQBBt0xskZd43Jiz1DzEOJmkekXTLc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789577275; c=relaxed/simple; bh=kNm7Nz196puQMkmVhm0OxCWNrw864lLADrF1Pp3iq2g=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=ovsE786t6nJ1Jxm4Jiz1QPP8OGe0sDthOL4ttp6ocZ82cri1pErBE+fTxua0d4xVnnbhOnOtu8QEYouWMpmhb3yJcYnpKkB/zj3TQq9hyS0xSFD24ZUbKgyMTx8fu/JUl21SFaGkkPsSIR37/XTR0EH32fjlE5eGtxP5HPTvaZM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ukcRkhqG; 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="ukcRkhqG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF2FC1F00898; Wed, 16 Sep 2026 16:47:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789577259; bh=cHy6NRGXSXGb1WHdXIU9+CCEVfCO5bD4tCjpAchBcto=; h=Subject:To:Cc:From:Date; b=ukcRkhqGdSL2ovvKuT9qxjZkEnq4rSMtgDXBjiJSApL2uD+MrL5tUNCOCPGG1IqZe p+5edVfQ6UCQFIfAJ09X0hZ+OidQwJmuYGpMhiY2X5zPm//1iH/wMONW76WF/lqimQ QG5hskpBjUywEIP+RfH1ZpjcQ1gQGiA9lzCt1vqQ= Subject: FAILED: patch "[PATCH] smb: client: pin DFS superblock in iterator callback" failed to apply to 5.15-stable tree To: kmehltretter@gmail.com,pc@manguebit.org Cc: From: Date: Wed, 16 Sep 2026 17:41:44 +0100 Message-ID: <2026091644-acid-unclasp-cda8@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 5.15-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-5.15.y git checkout FETCH_HEAD git cherry-pick -x d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818 # git commit -s git send-email --to '' --in-reply-to '2026091644-acid-unclasp-cda8@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d806d5a85dcbe2a0f181b2f0f9f61ddfbefa1818 Mon Sep 17 00:00:00 2001 From: Karl Mehltretter Date: Wed, 2 Sep 2026 20:28:14 +0200 Subject: [PATCH] smb: client: pin DFS superblock in iterator callback tcon_super_cb() stores a raw superblock pointer, but __cifs_get_super() takes its active reference only after iterate_supers_type() has dropped s_umount and its passive reference. Concurrent DFS automount expiry can therefore free the superblock before cifs_sb_active() uses it. A deterministic KASAN test reproduces the race as: BUG: KASAN: slab-use-after-free in cifs_sb_active+0x77/0x80 The same test passes with this change applied. Take the active reference in the callback while iterate_supers_type() still holds s_umount shared. cifs_put_tcp_super() remains the matching release. Fixes: bacd704a95ad ("cifs: handle prefix paths in reconnect") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Karl Mehltretter Signed-off-by: Paulo Alcantara diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c index 46e1382e8e04..d4db3f91a91f 100644 --- a/fs/smb/client/misc.c +++ b/fs/smb/client/misc.c @@ -891,8 +891,14 @@ static void tcon_super_cb(struct super_block *sb, void *arg) t1->ses->dfs_root_ses == t2->ses->dfs_root_ses) && t1->ses->server == t2->ses->server && t2->origin_fullpath && - dfs_src_pathname_equal(t2->origin_fullpath, t1->origin_fullpath)) + dfs_src_pathname_equal(t2->origin_fullpath, t1->origin_fullpath)) { + /* + * Take the active reference while iterate_supers_type() still + * holds s_umount shared. + */ + cifs_sb_active(sb); sd->sb = sb; + } spin_unlock(&t2->tc_lock); } @@ -909,15 +915,8 @@ static struct super_block *__cifs_get_super(void (*f)(struct super_block *, void for (; *fs_type; fs_type++) { iterate_supers_type(*fs_type, f, &sd); - if (sd.sb) { - /* - * Grab an active reference in order to prevent automounts (DFS links) - * of expiring and then freeing up our cifs superblock pointer while - * we're doing failover. - */ - cifs_sb_active(sd.sb); + if (sd.sb) return sd.sb; - } } pr_warn_once("%s: could not find dfs superblock\n", __func__); return ERR_PTR(-EINVAL);