From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta0.migadu.com (out-176.mta0.migadu.com [91.218.175.176]) (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 5BB1D6A349 for ; Tue, 6 Feb 2024 14:10:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707228616; cv=none; b=TDXZSppjQ0/E9jUY7fpkRTI56lf2KwnDith6n3O8Nq9VLNDaBkoKHcvkwsa4+hzOKJjEGii2/wUx3P2I8sP6uXupdf9vdHHc3thrCSdJKJXeu9e9UTnOeBUvIQjcbUixYL2tR28uCCh9R1etSNbvDjsR0n40niGGdmZhpNih1Hk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707228616; c=relaxed/simple; bh=cZeQl+T2HhEdGamQaRbIIa2pc/7wCTGf87gW2IW+1sI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=m/AluZbV687gm8U7vH0sLt2zmYgQ6HzC0vz5bAmTBE0LgEtY6iQMGpiB6hEtneo/OlwHqgxJdpC/fw/PjoCIlyt8Jl34E1QALjfA1g0Jy853m8hUvfvJmZeTW9srpT5hIYTpn2nT6ZzeKBkxGhMQ9eh/JgcJuCcx7BvLHbtUU0g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=erznLLVv; arc=none smtp.client-ip=91.218.175.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="erznLLVv" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1707228612; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2iB64trQ9tMkLCadbXXhUKodOl8BVJTxT7fnE2qC/6I=; b=erznLLVvMSxVXTzh+lT+1nvzrsu2SG9SpcbxDaXlly0mk1gTeVFotSL8Ojj0G7nAXPAlzz Es46SAu6k5PSm05jMr9PkU4+dL2jOJEe7tCPjsiJeoNoor/VDdTFRpE6SqNVrLCUjuT4QA TuxMWoNWG3jgHhdDFdNCZrdg8QjJvp4= Date: Tue, 6 Feb 2024 14:10:05 +0000 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [patch net] dpll: fix possible deadlock during netlink dump operation Content-Language: en-US To: Jiri Pirko , netdev@vger.kernel.org Cc: arkadiusz.kubalewski@intel.com References: <20240206125145.354557-1-jiri@resnulli.us> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Vadim Fedorenko In-Reply-To: <20240206125145.354557-1-jiri@resnulli.us> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 06/02/2024 12:51, Jiri Pirko wrote: > From: Jiri Pirko > > Recently, I've been hitting following deadlock warning during dpll pin > dump: > > [52804.637962] ====================================================== > [52804.638536] WARNING: possible circular locking dependency detected > [52804.639111] 6.8.0-rc2jiri+ #1 Not tainted > [52804.639529] ------------------------------------------------------ > [52804.640104] python3/2984 is trying to acquire lock: > [52804.640581] ffff88810e642678 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}, at: netlink_dump+0xb3/0x780 > [52804.641417] > but task is already holding lock: > [52804.642010] ffffffff83bde4c8 (dpll_lock){+.+.}-{3:3}, at: dpll_lock_dumpit+0x13/0x20 > [52804.642747] > which lock already depends on the new lock. > > [52804.643551] > the existing dependency chain (in reverse order) is: > [52804.644259] > -> #1 (dpll_lock){+.+.}-{3:3}: > [52804.644836] lock_acquire+0x174/0x3e0 > [52804.645271] __mutex_lock+0x119/0x1150 > [52804.645723] dpll_lock_dumpit+0x13/0x20 > [52804.646169] genl_start+0x266/0x320 > [52804.646578] __netlink_dump_start+0x321/0x450 > [52804.647056] genl_family_rcv_msg_dumpit+0x155/0x1e0 > [52804.647575] genl_rcv_msg+0x1ed/0x3b0 > [52804.648001] netlink_rcv_skb+0xdc/0x210 > [52804.648440] genl_rcv+0x24/0x40 > [52804.648831] netlink_unicast+0x2f1/0x490 > [52804.649290] netlink_sendmsg+0x36d/0x660 > [52804.649742] __sock_sendmsg+0x73/0xc0 > [52804.650165] __sys_sendto+0x184/0x210 > [52804.650597] __x64_sys_sendto+0x72/0x80 > [52804.651045] do_syscall_64+0x6f/0x140 > [52804.651474] entry_SYSCALL_64_after_hwframe+0x46/0x4e > [52804.652001] > -> #0 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}: > [52804.652650] check_prev_add+0x1ae/0x1280 > [52804.653107] __lock_acquire+0x1ed3/0x29a0 > [52804.653559] lock_acquire+0x174/0x3e0 > [52804.653984] __mutex_lock+0x119/0x1150 > [52804.654423] netlink_dump+0xb3/0x780 > [52804.654845] __netlink_dump_start+0x389/0x450 > [52804.655321] genl_family_rcv_msg_dumpit+0x155/0x1e0 > [52804.655842] genl_rcv_msg+0x1ed/0x3b0 > [52804.656272] netlink_rcv_skb+0xdc/0x210 > [52804.656721] genl_rcv+0x24/0x40 > [52804.657119] netlink_unicast+0x2f1/0x490 > [52804.657570] netlink_sendmsg+0x36d/0x660 > [52804.658022] __sock_sendmsg+0x73/0xc0 > [52804.658450] __sys_sendto+0x184/0x210 > [52804.658877] __x64_sys_sendto+0x72/0x80 > [52804.659322] do_syscall_64+0x6f/0x140 > [52804.659752] entry_SYSCALL_64_after_hwframe+0x46/0x4e > [52804.660281] > other info that might help us debug this: > > [52804.661077] Possible unsafe locking scenario: > > [52804.661671] CPU0 CPU1 > [52804.662129] ---- ---- > [52804.662577] lock(dpll_lock); > [52804.662924] lock(nlk_cb_mutex-GENERIC); > [52804.663538] lock(dpll_lock); > [52804.664073] lock(nlk_cb_mutex-GENERIC); > [52804.664490] > > The issue as follows: __netlink_dump_start() calls control->start(cb) > with nlk->cb_mutex held. In control->start(cb) the dpll_lock is taken. > Then nlk->cb_mutex is released and taken again in netlink_dump(), while > dpll_lock still being held. That leads to ABBA deadlock when another > CPU races with the same operation. > > Fix this by moving dpll_lock taking into dumpit() callback which ensures > correct lock taking order. > > Fixes: 9d71b54b65b1 ("dpll: netlink: Add DPLL framework base functions") > Signed-off-by: Jiri Pirko Good catch, thanks! Reviewed-by: Vadim Fedorenko > --- > drivers/dpll/dpll_netlink.c | 20 ++++++-------------- > drivers/dpll/dpll_nl.c | 4 ---- > 2 files changed, 6 insertions(+), 18 deletions(-) > > diff --git a/drivers/dpll/dpll_netlink.c b/drivers/dpll/dpll_netlink.c > index 314bb3775465..4ca9ad16cd95 100644 > --- a/drivers/dpll/dpll_netlink.c > +++ b/drivers/dpll/dpll_netlink.c > @@ -1199,6 +1199,7 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > unsigned long i; > int ret = 0; > > + mutex_lock(&dpll_lock); > xa_for_each_marked_start(&dpll_pin_xa, i, pin, DPLL_REGISTERED, > ctx->idx) { > if (!dpll_pin_available(pin)) > @@ -1218,6 +1219,8 @@ int dpll_nl_pin_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > } > genlmsg_end(skb, hdr); > } > + mutex_unlock(&dpll_lock); > + > if (ret == -EMSGSIZE) { > ctx->idx = i; > return skb->len; > @@ -1373,6 +1376,7 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > unsigned long i; > int ret = 0; > > + mutex_lock(&dpll_lock); > xa_for_each_marked_start(&dpll_device_xa, i, dpll, DPLL_REGISTERED, > ctx->idx) { > hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, > @@ -1389,6 +1393,8 @@ int dpll_nl_device_get_dumpit(struct sk_buff *skb, struct netlink_callback *cb) > } > genlmsg_end(skb, hdr); > } > + mutex_unlock(&dpll_lock); > + > if (ret == -EMSGSIZE) { > ctx->idx = i; > return skb->len; > @@ -1439,20 +1445,6 @@ dpll_unlock_doit(const struct genl_split_ops *ops, struct sk_buff *skb, > mutex_unlock(&dpll_lock); > } > > -int dpll_lock_dumpit(struct netlink_callback *cb) > -{ > - mutex_lock(&dpll_lock); > - > - return 0; > -} > - > -int dpll_unlock_dumpit(struct netlink_callback *cb) > -{ > - mutex_unlock(&dpll_lock); > - > - return 0; > -} > - > int dpll_pin_pre_doit(const struct genl_split_ops *ops, struct sk_buff *skb, > struct genl_info *info) > { > diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c > index eaee5be7aa64..1e95f5397cfc 100644 > --- a/drivers/dpll/dpll_nl.c > +++ b/drivers/dpll/dpll_nl.c > @@ -95,9 +95,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { > }, > { > .cmd = DPLL_CMD_DEVICE_GET, > - .start = dpll_lock_dumpit, > .dumpit = dpll_nl_device_get_dumpit, > - .done = dpll_unlock_dumpit, > .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP, > }, > { > @@ -129,9 +127,7 @@ static const struct genl_split_ops dpll_nl_ops[] = { > }, > { > .cmd = DPLL_CMD_PIN_GET, > - .start = dpll_lock_dumpit, > .dumpit = dpll_nl_pin_get_dumpit, > - .done = dpll_unlock_dumpit, > .policy = dpll_pin_get_dump_nl_policy, > .maxattr = DPLL_A_PIN_ID, > .flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DUMP,