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 EC79D4195AF for ; Thu, 9 Jul 2026 17:40:41 +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=1783618843; cv=none; b=MJNGcYedAYXtUE67ZrvC+B2mLpa1sQbhGs/m3JpSDWV5JFPVDwogQmEod7VJ7iAW/hl7/A4qu6PAfCd8jjTMI7aaO3NNWIbP7MwgV0DvjoE1Bdx4gyfJb01IahY+3IqQg2JrAyoBIJJrHuMM5UwShJQdxAI9DmBVBJnEkiumTTQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783618843; c=relaxed/simple; bh=TdjDz0QPIisYg2PRMpA6G2KXuaNaSDOKOQSW4HZKINQ=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=k1Mapr/luS0KkY0JQoT14nU+yhALr49HKRgorWPdvx8VX/E+heZS1qSw/2WMkBC4zogJjjn0EX9T5YNtYZXb/w28DyIFQTJQRX7z3qrKYOpfYE9QNi7mhs5C6XyB1rULnx9AN933aTIJ+r/9QjEGndVVEmnaRq4VSsscWX9eBhs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NIuW0SA2; 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="NIuW0SA2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 561A31F00A3E; Thu, 9 Jul 2026 17:40:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783618841; bh=q2/sBPW2xQmXWLCmo8oxZcbQDGqZmXMQvI1RUCljaq4=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=NIuW0SA2aLpFAVvKA5nzDsMerZxomyI9gue1Wtpun8glfjYSTGvZWvz5hcgsGm/g7 A12r/d92Rj9IpAnSBVp7RE6ebSh5I6QdFFDTY3rPStk+Os7qmTjKR1Yh68Aessvhvi iAU+j5voLYAA0d+pZJ0Z8wVKpn9XHJS3V9QIzzkgwpVObzQbg9HJT6ecc1DwB6muJi a0uWySvoUxSl4W5SysI+xJ41UxeMDqLIg3YXUiQzjs4h6PVH19CIq0lnI1xldMrFjX NIHfluBHluSedob0O+ZDlbI+nRvxY2s64Ad9SWwsXR1LGGlTjYFfeZ/3iKuO6MJKK0 uNE5XqnHXlKPQ== From: Chuck Lever Date: Thu, 09 Jul 2026 13:40:27 -0400 Subject: [PATCH v4 4/9] NFSD: Prevent client use-after-free during export state revocation Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260709-cel-v4-4-1d519d9be0cb@kernel.org> References: <20260709-cel-v4-0-1d519d9be0cb@kernel.org> In-Reply-To: <20260709-cel-v4-0-1d519d9be0cb@kernel.org> To: Jeff Layton , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, Chuck Lever X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=2102; i=cel@kernel.org; h=from:subject:message-id; bh=TdjDz0QPIisYg2PRMpA6G2KXuaNaSDOKOQSW4HZKINQ=; b=owEBbQKS/ZANAwAKATNqszNvZn+XAcsmYgBqT90V+LLeH3RzgI+Y5grsaGBPyZcpsqNKm/iV7 pkG0NEfh92JAjMEAAEKAB0WIQQosuWwEobfJDzyPv4zarMzb2Z/lwUCak/dFQAKCRAzarMzb2Z/ l/seEACAaPf7Wy5QCV7O+jnOETqURdhILCGemlN5UDSAdhF2jHt5rlt+bDS3naeqa/uAi/dEV6t WRQuYuGgdgtuVz3BGIZnWEUmvhY+1hgwRyeytDDuQ5Me+6wf7H1iIy3VLWATiswP474buR6Rl6B iC9zsVeZMUZc2XXc22Pqz6G6bL4Tyeh5AJwX0mL+/GoEqZQEn0EKHqbwmsuBZwkjov4Fo9sAY+6 JEZUOwMRTwaethD8uXI12p/34q8yOWzZWHf+0s6XOjnD8lOHDKz4qGtSkwZUy8fzvuyLLG4LPZ7 zErpul/sC0VBjPzXoMwmy5v3VNELuSDTJJwLpjRuyHr4S0ozHEVj5A3Uba1IXoP9yiNjvc/c4ud T+UFFHWDNVfVrIP5wNg3OSPz4DJRIEJH6VOH76E1vqRxADvwnpz6qgr0h9YUZ7TFJdC+1eHcx8s wAa5XiY1lWwrP/Yiz+YVmVbdYeyCGuk2voIWTiVpXxG8rlAJfA4hONseNzW2FAc8UzO1mHHeBY3 ycR9qKWGz8iqbYOn+IAMKUoLljXQNqz6WeMCs2ITOJ0dK28qm9ZAAwiAu3zbADhGlj2Oxc+Deq1 o1ZNBVupeRVhmmmoBO27+nYLRjweJmgxvNkwRt8X0LXRImXWWzHstkHjWPC9n0IiM/kZIaXbwRC cyV6TRNAoT9KSpA== X-Developer-Key: i=cel@kernel.org; a=openpgp; fpr=28B2E5B01286DF243CF23EFE336AB3336F667F97 nfsd4_revoke_export_states() has the same use-after-free as nfsd4_revoke_states(): it drops nn->client_lock across revoke_one_stid() and the following read of clp->cl_minorversion, but the stateid reference it holds does not pin the client. A teardown racing the dropped lock can free the client while revoke_one_stid() still dereferences it. exportfs -u drives this path through NFSD_CMD_UNLOCK_EXPORT, so an administrator removing an export can race a client expiry. Skip a client that is already expiring and otherwise pin it with cl_rpc_users under client_lock before dropping the lock, matching nfsd4_revoke_states(). Fixes: 2eac189bb059 ("NFSD: Add NFSD_CMD_UNLOCK_EXPORT netlink command") Reviewed-by: NeilBrown Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- fs/nfsd/nfs4state.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 565fa2ff5ba5..9de535a2a4bb 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -2055,10 +2055,14 @@ void nfsd4_revoke_export_states(struct nfsd_net *nn, const struct path *path) struct nfs4_client *clp; retry: list_for_each_entry(clp, head, cl_idhash) { - struct nfs4_stid *stid = find_one_export_stid( - clp, path, - sc_types); + struct nfs4_stid *stid; + + /* Skip or pin clp as in nfsd4_revoke_states(). */ + if (is_client_expired(clp)) + continue; + stid = find_one_export_stid(clp, path, sc_types); if (stid) { + atomic_inc(&clp->cl_rpc_users); spin_unlock(&nn->client_lock); revoke_one_stid(nn, clp, stid); nfs4_put_stid(stid); @@ -2066,6 +2070,9 @@ void nfsd4_revoke_export_states(struct nfsd_net *nn, const struct path *path) if (clp->cl_minorversion == 0) nn->nfs40_last_revoke = ktime_get_boottime_seconds(); + if (atomic_dec_and_test(&clp->cl_rpc_users) && + is_client_expired(clp)) + wake_up_all(&expiry_wq); goto retry; } } -- 2.54.0