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 EA7293FA5E6 for ; Wed, 16 Sep 2026 08:08:14 +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=1789546099; cv=none; b=K51oYHxGyQn0u8RMBlFYG6rEST0fZTrOodG218NzLfs2wyaMxcDaFfobQCVANmp7mjcCzvNa1glhW17L7fwxvZjpa4xXEeIUXDatw6uUwllJrSKVrsV1/gfWnYv1a3U0xlwlGMU7onhLC11B1mtzha7BH7OxyMnHSwtSXx6AWTU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789546099; c=relaxed/simple; bh=CTiivJUbnWamNAkT80iRPiicHysQQ1OOKhnUTGrCOOs=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=maZ4Yf2DI067TIoKY8/55jxFomqOwTnenXCJDhG3vx2mPAOmz81DKdf3LH/79acjy6i+ZzfmyCw3wqYT2SQwJ0K7sR5L2xpxtPY3QsrIz4LJcJ9UHGn7HkPO3ab3NzWOgsy7VPcfYca0V1CEvPyarIFMxvCPwoRbiMnibdxZs0s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mzusc1J8; 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="mzusc1J8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEF6F1F0089B; Wed, 16 Sep 2026 08:07:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789546090; bh=Q50e4Wn7/q6yA5KiWfVDkP7oTi0jZYnvdxrepuwM4xo=; h=Subject:To:Cc:From:Date; b=mzusc1J8SRM5DA31nGYM+GPhUoIBvd4iiBIJS785mFGMZmyRYi5ts6fQOLWMe9s5H eCYkFkn9G4+KYCRqsWuKTqvdrmNg0ps9mop1iA/W4Q9CS0kkFOISNSohnEh+K0LLJ+ 09/k6CXTO+BWHoXrvooi8nYtKIVLMf/KAHQ1miIg= Subject: FAILED: patch "[PATCH] configfs: unhash the dentry before dropping the item in rmdir" failed to apply to 6.18-stable tree To: vasilisalmpanis@gmail.com,leitao@debian.org Cc: From: Date: Wed, 16 Sep 2026 09:05:56 +0100 Message-ID: <2026091656-showman-zit-60ac@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 6.18-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-6.18.y git checkout FETCH_HEAD git cherry-pick -x f06c2d26d1999d37e93299db0ecead04ca7d0b9f # git commit -s git send-email --to '' --in-reply-to '2026091656-showman-zit-60ac@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From f06c2d26d1999d37e93299db0ecead04ca7d0b9f Mon Sep 17 00:00:00 2001 From: Vasileios Almpanis Date: Thu, 30 Jul 2026 11:30:25 +0200 Subject: [PATCH] configfs: unhash the dentry before dropping the item in rmdir configfs_get_config_item() treats a hashed dentry as proof that sd->s_element is a live config_item. configfs_rmdir() breaks that: simple_rmdir() leaves the dentry hashed, the last reference to the item is dropped right after, and the dentry is only unhashed by d_delete() once ->rmdir() has returned. configfs_symlink() resolves its target holding no lock on it, so get_target() can land in that window: BUG: KASAN: slab-use-after-free in config_item_get+0x26/0x90 get_target fs/configfs/symlink.c:128 [inline] configfs_symlink+0x4ab/0x1030 fs/configfs/symlink.c:185 Unhash in configfs_remove_dir(), while the item is still guaranteed to be there. A reference obtained just before that stays harmless, as create_link() rechecks CONFIGFS_USET_DROPPING, already set by configfs_detach_prep(). Both configfs_unregister_subsystem() paths d_drop() after detaching, so this only makes rmdir match them. Reported-by: syzbot+6b16e3d085833cbf3e25@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6b16e3d085833cbf3e25 Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Cc: stable@vger.kernel.org Signed-off-by: Vasileios Almpanis Tested-by: Breno Leitao Reviewed-by: Breno Leitao Link: https://patch.msgid.link/20260730093435.195441-3-vasilisalmpanis@gmail.com Signed-off-by: Breno Leitao diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 3c88f13f1ca2..eda80c2a2d38 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -416,6 +416,15 @@ static void configfs_remove_dir(struct dentry *d) if (d_really_is_positive(d)) { if (unlikely(simple_rmdir(d_inode(parent), d))) pr_warn("remove_dir (%pd): attributes remain", d); + else + /* + * configfs_get_config_item() takes a hashed dentry as + * proof that ->s_element is still alive. Our caller + * is about to drop the last reference to the item and + * the VFS will not unhash until after we return, so + * unhash it here. + */ + d_drop(d); } pr_debug(" o %pd removing done (%d)\n", d, d_count(d));