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 87956286420; Wed, 8 Oct 2025 13:52:35 +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=1759931555; cv=none; b=lZ2TKCvu4/9XgpMAztX9Q5hBEgyb3K3DEo3BQwCxRr84HZreueXicQgKB05VxDB5adkrq+jMfhKVE4Cb/ouaGMUUHHyjktr2pVrlF2xNoSihaVDlbeciE92cM264L2IQ/NJkWu1Ek/bGt7akp8j8PrMf7IBrbCQZNTnSP0niZ60= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759931555; c=relaxed/simple; bh=+GHi5WhDcOXlMuzmlmOVyStTbe9T6QIfMAIF7O2fc6o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hmf0ACZQ4KvtUidltg9+I9kUd4NZx47/O350LJ3PivVjXthzFRAbUze7MrIqiNuunSlQdCu/zjVU/0p6HiyeCGIQyG7+LgEYIJZ3ltypaLOR9Z6+wb/4PfFUE2jWTTJLBnjotOO4Z2lVaGucRyMNLzvjiIzpehs/NdAYDLze0w4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=XZrbf5M1; 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="XZrbf5M1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6301DC4CEF4; Wed, 8 Oct 2025 13:52:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759931555; bh=+GHi5WhDcOXlMuzmlmOVyStTbe9T6QIfMAIF7O2fc6o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XZrbf5M1+IVFZ8wqFpQXRIDoAPhw35gN8cL4ZkRmWmZVd13go+ui3d8FHryW1cJ4w v4KN5qC/UZu1ctqhYZkXIJ2DTwMXNcROVmEKvfhMCLgDo7JHSaHJ5vDfq5UND+WtG0 3w8gA6+cOqhlbGeQztxU61Q7vBIdeyEPxq/n1+pInBi22NYnzUB95kAxUZsdr97HFJ BgR6Es8ehhB93ZJIJ0zQxcA6EKLkrl2A4C1JhYhCnLSF2vCK30MJDdKDJGWIYmvLTx SFEC/V7YZV5rAfvTW7V/ez47/S0zwoklEKsI7ZarphgpPYLw4CvapmNXORAzeui+KX PgLqrLC8gJsxA== From: Chuck Lever To: NeilBrown , Jeff Layton , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: , tianshuo han , stable@vger.kernel.org Subject: [PATCH v6 1/6] nfsd: fix refcount leak in nfsd_set_fh_dentry() Date: Wed, 8 Oct 2025 09:52:25 -0400 Message-ID: <20251008135230.2629-2-cel@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251008135230.2629-1-cel@kernel.org> References: <20251008135230.2629-1-cel@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: NeilBrown nfsd exports a "pseudo root filesystem" which is used by NFSv4 to find the various exported filesystems using LOOKUP requests from a known root filehandle. NFSv3 uses the MOUNT protocol to find those exported filesystems and so is not given access to the pseudo root filesystem. If a v3 (or v2) client uses a filehandle from that filesystem, nfsd_set_fh_dentry() will report an error, but still stores the export in "struct svc_fh" even though it also drops the reference (exp_put()). This means that when fh_put() is called an extra reference will be dropped which can lead to use-after-free and possible denial of service. Normal NFS usage will not provide a pseudo-root filehandle to a v3 client. This bug can only be triggered by the client synthesising an incorrect filehandle. To fix this we move the assignments to the svc_fh later, after all possible error cases have been detected. Reported-and-tested-by: tianshuo han Fixes: ef7f6c4904d0 ("nfsd: move V4ROOT version check to nfsd_set_fh_dentry()") Signed-off-by: NeilBrown Reviewed-by: Jeff Layton Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever --- fs/nfsd/nfsfh.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index 3eb724ec9566..ed85dd43da18 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -269,9 +269,6 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, dentry); } - fhp->fh_dentry = dentry; - fhp->fh_export = exp; - switch (fhp->fh_maxsize) { case NFS4_FHSIZE: if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR) @@ -293,6 +290,9 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, goto out; } + fhp->fh_dentry = dentry; + fhp->fh_export = exp; + return 0; out: exp_put(exp); -- 2.51.0