From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta1.migadu.com (out-179.mta1.migadu.com [95.215.58.179]) (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 E036276036 for ; Wed, 21 Aug 2024 18:45:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724265909; cv=none; b=AwiPMLkTwg4W4ONsDrm+iwsaO74efYnCrfoYlgrC8uI7s5BQ6Wid1sO9GBwicH6lkuZHZPTVrjFNsrEoXGNGYPwOLxDJunXTfdmSTEMfhBvZ97VMUr+aHIObmhs6TCwdw82O41T1c5gf40nBD7pbzKQfBJI+Na+NNfoewC1UY/o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724265909; c=relaxed/simple; bh=TX5s92+TVhuZMU9AZQyjIAcTZ2oRFVtucS+9h5RV9cM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YxOqxU6xTd+MqoRTkmoIvRcN1EZx5cGcKV/fXJXFqVKp9eL5n/zLQjsQw+a2+AyT5JZGicdzO7DAuOi/6/oR2xoLAeTE2mXxsGtSmH3jqeAyecsv+r7C3aNEiDV/Y9dEke187U0RIjFropqyX3b7xWt5e2X+37CjjMmGUskNt1s= 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=fWi6u5Oi; arc=none smtp.client-ip=95.215.58.179 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="fWi6u5Oi" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1724265904; 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=6xYdDGp9cZcugtgHBeqcbLyntEez0XWBUyxTHat7Hc8=; b=fWi6u5OiQ+Kqss7H6N0eyuu56xh6u+34e0xCWYECGBCxuRkTqNm+D7wcD0AhTWM8jiEXx0 v5s81aW8FcrLngLXE3thncpOMYUMc6YyayVg7hUBwm1v3id4LZJCTlbLfbm63i2KI7lWCd 4Kz9UHTNkxvcMBkewyXBCm1+XPX6Iiw= Date: Wed, 21 Aug 2024 11:44:52 -0700 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH net v4] bpf, net: Check cgroup_bpf_enabled() only once in do_sock_getsockopt() Content-Language: en-GB To: Tze-nan Wu , netdev@vger.kernel.org, bpf@vger.kernel.org, "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Matthias Brugger , AngeloGioacchino Del Regno , Stanislav Fomichev Cc: bobule.chang@mediatek.com, wsd_upstream@mediatek.com, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, Kuniyuki Iwashima , Yanghui Li , Cheng-Jui Wang , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , KP Singh , Hao Luo , Jiri Olsa , linux-arm-kernel@lists.infradead.org References: <20240821093016.2533-1-Tze-nan.Wu@mediatek.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20240821093016.2533-1-Tze-nan.Wu@mediatek.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 8/21/24 2:30 AM, Tze-nan Wu wrote: > The return value from `cgroup_bpf_enabled(CGROUP_GETSOCKOPT)` can change > between the invocations of `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN` and > `BPF_CGROUP_RUN_PROG_GETSOCKOPT`. > > If `cgroup_bpf_enabled(CGROUP_GETSOCKOPT)` changes from "false" to > "true" between the invocations of `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN` and > `BPF_CGROUP_RUN_PROG_GETSOCKOPT`, `BPF_CGROUP_RUN_PROG_GETSOCKOPT` will > receive an -EFAULT from `__cgroup_bpf_run_filter_getsockopt(max_optlen=0)` > due to `get_user()` was not reached in `BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN`. > > Scenario shown as below: > > `process A` `process B` > ----------- ------------ > BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN > enable CGROUP_GETSOCKOPT > BPF_CGROUP_RUN_PROG_GETSOCKOPT (-EFAULT) > > To prevent this, invoke `cgroup_bpf_enabled()` only once and cache the > result in a newly added local variable `enabled`. > Both `BPF_CGROUP_*` macros in `do_sock_getsockopt` will then check their > condition using the same `enabled` variable as the condition variable, > instead of using the return values from `cgroup_bpf_enabled` called by > themselves as the condition variable(which could yield different results). > This ensures that either both `BPF_CGROUP_*` macros pass the condition > or neither does. > > Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks") > Co-developed-by: Yanghui Li > Signed-off-by: Yanghui Li > Co-developed-by: Cheng-Jui Wang > Signed-off-by: Cheng-Jui Wang > Signed-off-by: Tze-nan Wu > --- > > Chagnes from v1 to v2: https://lore.kernel.org/all/20240819082513.27176-1-Tze-nan.Wu@mediatek.com/ > Instead of using cgroup_lock in the fastpath, invoke cgroup_bpf_enabled > only once and cache the value in the newly added variable `enabled`. > `BPF_CGROUP_*` macros in do_sock_getsockopt can then both check their > condition with the new variable `enable`, ensuring that either they both > passing the condition or both do not. > > Chagnes from v2 to v3: https://lore.kernel.org/all/20240819155627.1367-1-Tze-nan.Wu@mediatek.com/ > Hide cgroup_bpf_enabled in the macro, and some modifications to adapt > the coding style. > > Chagnes from v3 to v4: https://lore.kernel.org/all/20240820092942.16654-1-Tze-nan.Wu@mediatek.com/ > Add bpf tag to subject, and Fixes tag in body. > > --- > include/linux/bpf-cgroup.h | 15 ++++++++------- > net/socket.c | 5 +++-- > 2 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h > index fb3c3e7181e6..5afa2ac76aae 100644 > --- a/include/linux/bpf-cgroup.h > +++ b/include/linux/bpf-cgroup.h > @@ -390,20 +390,20 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk, > __ret; \ > }) > > -#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen) \ > +#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, enabled) \ > ({ \ > int __ret = 0; \ > - if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT)) \ > + enabled = cgroup_bpf_enabled(CGROUP_GETSOCKOPT); \ > + if (enabled) \ > copy_from_sockptr(&__ret, optlen, sizeof(int)); \ > __ret; \ > }) > > #define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, optlen, \ > - max_optlen, retval) \ > + max_optlen, retval, enabled) \ > ({ \ > int __ret = retval; \ > - if (cgroup_bpf_enabled(CGROUP_GETSOCKOPT) && \ > - cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT)) \ > + if (enabled && cgroup_bpf_sock_enabled(sock, CGROUP_GETSOCKOPT)) \ > if (!(sock)->sk_prot->bpf_bypass_getsockopt || \ > !INDIRECT_CALL_INET_1((sock)->sk_prot->bpf_bypass_getsockopt, \ > tcp_bpf_bypass_getsockopt, \ > @@ -518,9 +518,10 @@ static inline int bpf_percpu_cgroup_storage_update(struct bpf_map *map, > #define BPF_CGROUP_RUN_PROG_SOCK_OPS(sock_ops) ({ 0; }) > #define BPF_CGROUP_RUN_PROG_DEVICE_CGROUP(atype, major, minor, access) ({ 0; }) > #define BPF_CGROUP_RUN_PROG_SYSCTL(head,table,write,buf,count,pos) ({ 0; }) > -#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen) ({ 0; }) > +#define BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, enabled) ({ 0; }) > #define BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock, level, optname, optval, \ > - optlen, max_optlen, retval) ({ retval; }) > + optlen, max_optlen, retval, \ > + enabled) ({ retval; }) > #define BPF_CGROUP_RUN_PROG_GETSOCKOPT_KERN(sock, level, optname, optval, \ > optlen, retval) ({ retval; }) > #define BPF_CGROUP_RUN_PROG_SETSOCKOPT(sock, level, optname, optval, optlen, \ > diff --git a/net/socket.c b/net/socket.c > index fcbdd5bc47ac..0b465dc8a789 100644 > --- a/net/socket.c > +++ b/net/socket.c > @@ -2363,6 +2363,7 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level, > int optname, sockptr_t optval, sockptr_t optlen) > { > int max_optlen __maybe_unused; > + bool enabled __maybe_unused; > const struct proto_ops *ops; > int err; > > @@ -2371,7 +2372,7 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level, > return err; > > if (!compat) > - max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen); > + max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, enabled); Here, 'enabled' is actually assigned with a value in the macro. I am not sure whether this is a common practice or not. At least from macro, it is not clear about this. Maybe we can do max_optlen = BPF_CGROUP_GETSOCKOPT_MAX_OPTLEN(optlen, &enabled); The &enabled signals that its value could change. And indeed the macro will store the proper value to &enabled properly. Just my 2 cents. > > ops = READ_ONCE(sock->ops); > if (level == SOL_SOCKET) { > @@ -2390,7 +2391,7 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level, > if (!compat) > err = BPF_CGROUP_RUN_PROG_GETSOCKOPT(sock->sk, level, optname, > optval, optlen, max_optlen, > - err); > + err, enabled); > > return err; > }