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 C01FD51991E for ; Wed, 16 Sep 2026 14:39:34 +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=1789569576; cv=none; b=nySrH3QK2ISA5acRp+VJkNIjtMbj694ne8drGk0FQQiEMWROcaoYunR3Xw/2ntoGwAsSNjfUDWXD3L/2yfi1WivYZNWsIADb2i7U4QhkrC53kwLaeGuQXcxHIK1XuWejoJi8aGp7poytE0TzclhgTlwp0Inl5wAjZdie3cQOmZc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789569576; c=relaxed/simple; bh=/WhVugQKzh4InElXkfFP1+K0vcBOYsl86Q9Bj8i24hU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DTH3/0jYCnqT1UBvD5Sh+B+BWjd4/oxs1t9KdtCQJXFSKkC+0X+x2AqBaU0KJ8hUoDhGoCY5vUxUm/XJaZ/32wraqbdNeb2Ao1MCUFA/eKzz18eWxD81MEbZyjIRpvFRNOCG54Mcd+KtavCcMxE5SXgnB+3ms1qFZ8id6/MxsCE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KG/H4lJa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KG/H4lJa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D63491F000FF; Wed, 16 Sep 2026 14:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789569574; bh=PJZohl60zYZe9/g8t0WAKBeogPff7xZPLl9OJ9ZF+fE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=KG/H4lJaBNIcBgMcfRiUcOD79/LfPysNHIiLW/QEI9b+eOmIHgBh6Ilak7rczeMZD ZKhR1qZteuQeBCm1nt0jzcUWxGLN5DjC76IoTggQoEXRPgExDV5b+mrsXzcFzHUZDR Xze0x30FBQywsZ6E+C2glYF+Dh55uPgN1qM3taJRGH8sEyRTyI9SZBnBV//LBvHyAi ZiW7aHpwg3R36ZV956++A6QqqQ4OZWMzQZq4DiD3+alH2anV8hYcwSV5j7HFq/Z74/ v9Teg/Ld/0/ZvJe77v3PU+9A4H+YXo3WklnyduTbShEzNvFP3gAiCKBshQCABWQLfK xUG5Zm5Fr6Fag== From: Sasha Levin To: stable@vger.kernel.org Cc: Vasileios Almpanis , syzbot+6b16e3d085833cbf3e25@syzkaller.appspotmail.com, Breno Leitao , Sasha Levin Subject: [PATCH 6.18.y] configfs: unhash the dentry before dropping the item in rmdir Date: Wed, 16 Sep 2026 10:39:32 -0400 Message-ID: <20260916143932.3493496-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026091656-showman-zit-60ac@gregkh> References: <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-Transfer-Encoding: 8bit From: Vasileios Almpanis [ Upstream commit f06c2d26d1999d37e93299db0ecead04ca7d0b9f ] 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 [ adapted the configfs_remove_dir() change to the older remove_dir() helper. ] Signed-off-by: Sasha Levin --- fs/configfs/dir.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 68203952766e6..181de3ba835a5 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -401,8 +401,17 @@ static void remove_dir(struct dentry * d) configfs_remove_dirent(d); - if (d_really_is_positive(d)) - simple_rmdir(d_inode(parent),d); + if (d_really_is_positive(d)) { + if (!simple_rmdir(d_inode(parent), d)) + /* + * 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)); -- 2.53.0