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 5D97419E971; Mon, 23 Dec 2024 16:14:17 +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=1734970459; cv=none; b=kcEr/DSmTHrCDZhdmSYw4bEd7HqydENQUQxwsBXrL2NIQC8TC1k4D+M1Xp42jCyBiQGeAJ1rUhjjPYWIdVXaVLECaf27oRyTuK1cPTETUv5D55/iMJkLIIwe4E+clV6etJ+cyrgKT43aGoHbArc9l6k3sTLQBDkktlyh1b3c77Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734970459; c=relaxed/simple; bh=EVMpODJmp+BhVTl7mbK+MbS8Zrj2U1T7WXSSxPOD7kY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Lb3Fswreg2i//13/ulxW7WdlCSFzNCK4jX35ZCYpcsxtmDULeeJ78noKOxoutJuM+fPsgdKWnNncpsS4pkvv6y1SfQQJ1Fcg2msK20fbRmPGS18U8xGxPPaK8p32I4Jm2hKQMnyEU947gsGUiCxaS2QoMWDQdBraTuIcWDB+Zkg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nb280PrE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nb280PrE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2EC3BC4CED3; Mon, 23 Dec 2024 16:14:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734970457; bh=EVMpODJmp+BhVTl7mbK+MbS8Zrj2U1T7WXSSxPOD7kY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nb280PrECcjRBFVZdwMbs2Q/AqC3k1imm4jvuBpwF6J5hdpN3Mu2bEZ2ZeJD0iGmg quRIxCtnsmE9qmJfeo7fYSEW++d7JtjG25TutCDUHGVVmh1DJ5dzAnrC+0qg1TGyU4 QbgOoT65aGk6qRsFlSTE/8tLdOTJBKtNLy+W/RQ4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dexuan Cui , Michael Kelley , Wei Liu Subject: [PATCH 6.6 089/116] Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet Date: Mon, 23 Dec 2024 16:59:19 +0100 Message-ID: <20241223155403.024604153@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241223155359.534468176@linuxfoundation.org> References: <20241223155359.534468176@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Kelley commit 07a756a49f4b4290b49ea46e089cbe6f79ff8d26 upstream. If the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is fully initialized, we can hit the panic below: hv_utils: Registering HyperV Utility Driver hv_vmbus: registering driver hv_utils ... BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1 RIP: 0010:hv_pkt_iter_first+0x12/0xd0 Call Trace: ... vmbus_recvpacket hv_kvp_onchannelcallback vmbus_on_event tasklet_action_common tasklet_action handle_softirqs irq_exit_rcu sysvec_hyperv_stimer0 asm_sysvec_hyperv_stimer0 ... kvp_register_done hvt_op_read vfs_read ksys_read __x64_sys_read This can happen because the KVP/VSS channel callback can be invoked even before the channel is fully opened: 1) as soon as hv_kvp_init() -> hvutil_transport_init() creates /dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and register itself to the driver by writing a message KVP_OP_REGISTER1 to the file (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and reading the file for the driver's response, which is handled by hvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done(). 2) the problem with kvp_register_done() is that it can cause the channel callback to be called even before the channel is fully opened, and when the channel callback is starting to run, util_probe()-> vmbus_open() may have not initialized the ringbuffer yet, so the callback can hit the panic of NULL pointer dereference. To reproduce the panic consistently, we can add a "ssleep(10)" for KVP in __vmbus_open(), just before the first hv_ringbuffer_init(), and then we unload and reload the driver hv_utils, and run the daemon manually within the 10 seconds. Fix the panic by reordering the steps in util_probe() so the char dev entry used by the KVP or VSS daemon is not created until after vmbus_open() has completed. This reordering prevents the race condition from happening. Reported-by: Dexuan Cui Fixes: e0fa3e5e7df6 ("Drivers: hv: utils: fix a race on userspace daemons registration") Cc: stable@vger.kernel.org Signed-off-by: Michael Kelley Acked-by: Wei Liu Link: https://lore.kernel.org/r/20241106154247.2271-3-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20241106154247.2271-3-mhklinux@outlook.com> Signed-off-by: Greg Kroah-Hartman --- drivers/hv/hv_kvp.c | 6 ++++++ drivers/hv/hv_snapshot.c | 6 ++++++ drivers/hv/hv_util.c | 9 +++++++++ drivers/hv/hyperv_vmbus.h | 2 ++ include/linux/hyperv.h | 1 + 5 files changed, 24 insertions(+) --- a/drivers/hv/hv_kvp.c +++ b/drivers/hv/hv_kvp.c @@ -767,6 +767,12 @@ hv_kvp_init(struct hv_util_service *srv) */ kvp_transaction.state = HVUTIL_DEVICE_INIT; + return 0; +} + +int +hv_kvp_init_transport(void) +{ hvt = hvutil_transport_init(kvp_devname, CN_KVP_IDX, CN_KVP_VAL, kvp_on_msg, kvp_on_reset); if (!hvt) --- a/drivers/hv/hv_snapshot.c +++ b/drivers/hv/hv_snapshot.c @@ -388,6 +388,12 @@ hv_vss_init(struct hv_util_service *srv) */ vss_transaction.state = HVUTIL_DEVICE_INIT; + return 0; +} + +int +hv_vss_init_transport(void) +{ hvt = hvutil_transport_init(vss_devname, CN_VSS_IDX, CN_VSS_VAL, vss_on_msg, vss_on_reset); if (!hvt) { --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -141,6 +141,7 @@ static struct hv_util_service util_heart static struct hv_util_service util_kvp = { .util_cb = hv_kvp_onchannelcallback, .util_init = hv_kvp_init, + .util_init_transport = hv_kvp_init_transport, .util_pre_suspend = hv_kvp_pre_suspend, .util_pre_resume = hv_kvp_pre_resume, .util_deinit = hv_kvp_deinit, @@ -149,6 +150,7 @@ static struct hv_util_service util_kvp = static struct hv_util_service util_vss = { .util_cb = hv_vss_onchannelcallback, .util_init = hv_vss_init, + .util_init_transport = hv_vss_init_transport, .util_pre_suspend = hv_vss_pre_suspend, .util_pre_resume = hv_vss_pre_resume, .util_deinit = hv_vss_deinit, @@ -592,6 +594,13 @@ static int util_probe(struct hv_device * if (ret) goto error; + if (srv->util_init_transport) { + ret = srv->util_init_transport(); + if (ret) { + vmbus_close(dev->channel); + goto error; + } + } return 0; error: --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -370,12 +370,14 @@ void vmbus_on_event(unsigned long data); void vmbus_on_msg_dpc(unsigned long data); int hv_kvp_init(struct hv_util_service *srv); +int hv_kvp_init_transport(void); void hv_kvp_deinit(void); int hv_kvp_pre_suspend(void); int hv_kvp_pre_resume(void); void hv_kvp_onchannelcallback(void *context); int hv_vss_init(struct hv_util_service *srv); +int hv_vss_init_transport(void); void hv_vss_deinit(void); int hv_vss_pre_suspend(void); int hv_vss_pre_resume(void); --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1561,6 +1561,7 @@ struct hv_util_service { void *channel; void (*util_cb)(void *); int (*util_init)(struct hv_util_service *); + int (*util_init_transport)(void); void (*util_deinit)(void); int (*util_pre_suspend)(void); int (*util_pre_resume)(void);