From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 73537256C7E for ; Mon, 20 Oct 2025 17:29:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760981346; cv=none; b=VeH4ojQoRECjCwMZQwM45Zm42AwFBT8+nkCvrSQBt+MpOzdED2syCYaXVCXpzqQDKO1NuXEVpPeYEZsUNB4AU+w9EdyCIBo4cyeAhckagypF+FWAz+Cj7w/RMtBZx5rPmrpni9lAWJ2WZRRD53d2jAKGqb3AGG3FxCcdeEr76cI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760981346; c=relaxed/simple; bh=vXEDTyZpecp0OLhq8E+eHgqjd69iId5OfLVYWpsYI0s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BYwBfKXa0itVRliJM48+z2h9w+rVIZWkBkSeQPqwgRInFbHjhrBsAkWApRKodJyANNC9B3oDjmSqds1pvMAtvV2Y56MHa6/yzSYQA1SVoqhsmr6mTvFeg37sbOgqKCOKj7Wx5kKp0cj8swjHm8JG/Y0r2/KglaXHcd9FGIVUyYA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jiiCCs5I; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jiiCCs5I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 43BCFC116B1; Mon, 20 Oct 2025 17:29:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760981343; bh=vXEDTyZpecp0OLhq8E+eHgqjd69iId5OfLVYWpsYI0s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jiiCCs5I75E4gf5b28dLXgDetsGrPoyTsNZ1CnLDxdPwEHG5TpppJxwW+CdkIbkYC t632SwEUO55xTxMt+ZIg25TV5EW0rU57+WsV36eiJGig4ILN2DOJUVj9g4qdH7rKOo CZsksAiqmvGfxV4fzFTXP2ewPFWIbeCBdy3rJuvjfclXcNRLN+efSLhEjGeIDsBuvT xjOzFOAMIOb3xf+kvEOZ+5NCna73mdoTh/mknSH7yusWnKTNNa7tY95vzxphEImAo9 2QcJaBHVLv4VbXB0SBfWHCqTIXS1aA0LsQGDBgD2sSVQqOlz19j4XeHwCq6xfriO5s qRSlcGB5qnxSA== From: Sasha Levin To: stable@vger.kernel.org Cc: Jan Kara , syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com, Christian Brauner , Sasha Levin Subject: [PATCH 6.12.y 2/2] vfs: Don't leak disconnected dentries on umount Date: Mon, 20 Oct 2025 13:28:59 -0400 Message-ID: <20251020172900.1851256-2-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251020172900.1851256-1-sashal@kernel.org> References: <2025102038-hash-smashing-4b29@gregkh> <20251020172900.1851256-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jan Kara [ Upstream commit 56094ad3eaa21e6621396cc33811d8f72847a834 ] When user calls open_by_handle_at() on some inode that is not cached, we will create disconnected dentry for it. If such dentry is a directory, exportfs_decode_fh_raw() will then try to connect this dentry to the dentry tree through reconnect_path(). It may happen for various reasons (such as corrupted fs or race with rename) that the call to lookup_one_unlocked() in reconnect_one() will fail to find the dentry we are trying to reconnect and instead create a new dentry under the parent. Now this dentry will not be marked as disconnected although the parent still may well be disconnected (at least in case this inconsistency happened because the fs is corrupted and .. doesn't point to the real parent directory). This creates inconsistency in disconnected flags but AFAICS it was mostly harmless. At least until commit f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") which removed adding of most disconnected dentries to sb->s_anon list. Thus after this commit cleanup of disconnected dentries implicitely relies on the fact that dput() will immediately reclaim such dentries. However when some leaf dentry isn't marked as disconnected, as in the scenario described above, the reclaim doesn't happen and the dentries are "leaked". Memory reclaim can eventually reclaim them but otherwise they stay in memory and if umount comes first, we hit infamous "Busy inodes after unmount" bug. Make sure all dentries created under a disconnected parent are marked as disconnected as well. Reported-by: syzbot+1d79ebe5383fc016cf07@syzkaller.appspotmail.com Fixes: f1ee616214cb ("VFS: don't keep disconnected dentries on d_anon") CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Christian Brauner Signed-off-by: Sasha Levin --- fs/dcache.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/dcache.c b/fs/dcache.c index d81765352cf81..d7814142ba7db 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2486,6 +2486,8 @@ struct dentry *d_alloc_parallel(struct dentry *parent, spin_lock(&parent->d_lock); new->d_parent = dget_dlock(parent); hlist_add_head(&new->d_sib, &parent->d_children); + if (parent->d_flags & DCACHE_DISCONNECTED) + new->d_flags |= DCACHE_DISCONNECTED; spin_unlock(&parent->d_lock); retry: -- 2.51.0