From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (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 237862FE3A for ; Wed, 8 Nov 2023 23:11:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XzcAwJ5O" Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [IPv6:2001:41d0:1004:224b::b2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E7F72593 for ; Wed, 8 Nov 2023 15:11:44 -0800 (PST) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1699485101; 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=R382c0XDJR7dje3E6emnn6V+72FnVb0FvYJk9VxWZBE=; b=XzcAwJ5Oz12bx6xspzmVTl75p+m/5hfN6+u1VZdP02NITn2EVUc/O+cVtCHKuYj2rtMPqD LJVeTFMwAiW/+oc5+IGheau+Nzq/V431U9bFs5XnnpRxJtpglKEDRMK02KdTPlQYJQHTiX cttuNWBXLXC5LpvZqXOhiFnl7X3Ww88= Date: Wed, 8 Nov 2023 15:11:33 -0800 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf 01/11] bpf: Check rcu_read_lock_trace_held() before calling bpf map helpers Content-Language: en-US To: Hou Tao Cc: Alexei Starovoitov , Andrii Nakryiko , Song Liu , Hao Luo , Yonghong Song , Daniel Borkmann , KP Singh , Stanislav Fomichev , Jiri Olsa , John Fastabend , houtao1@huawei.com, bpf@vger.kernel.org References: <20231107140702.1891778-1-houtao@huaweicloud.com> <20231107140702.1891778-2-houtao@huaweicloud.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Martin KaFai Lau In-Reply-To: <20231107140702.1891778-2-houtao@huaweicloud.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 11/7/23 6:06 AM, Hou Tao wrote: > From: Hou Tao > > These three bpf_map_{lookup,update,delete}_elem() helpers are also > available for sleepable bpf program, so add the corresponding lock > assertion for sleepable bpf program, otherwise the following warning > will be reported when a sleepable bpf program manipulates bpf map under > interpreter mode (aka bpf_jit_enable=0): > > WARNING: CPU: 3 PID: 4985 at kernel/bpf/helpers.c:40 ...... > CPU: 3 PID: 4985 Comm: test_progs Not tainted 6.6.0+ #2 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) ...... > RIP: 0010:bpf_map_lookup_elem+0x54/0x60 > ...... > Call Trace: > > ? __warn+0xa5/0x240 > ? bpf_map_lookup_elem+0x54/0x60 > ? report_bug+0x1ba/0x1f0 > ? handle_bug+0x40/0x80 > ? exc_invalid_op+0x18/0x50 > ? asm_exc_invalid_op+0x1b/0x20 > ? __pfx_bpf_map_lookup_elem+0x10/0x10 > ? rcu_lockdep_current_cpu_online+0x65/0xb0 > ? rcu_is_watching+0x23/0x50 > ? bpf_map_lookup_elem+0x54/0x60 > ? __pfx_bpf_map_lookup_elem+0x10/0x10 > ___bpf_prog_run+0x513/0x3b70 > __bpf_prog_run32+0x9d/0xd0 > ? __bpf_prog_enter_sleepable_recur+0xad/0x120 > ? __bpf_prog_enter_sleepable_recur+0x3e/0x120 > bpf_trampoline_6442580665+0x4d/0x1000 > __x64_sys_getpgid+0x5/0x30 > ? do_syscall_64+0x36/0xb0 > entry_SYSCALL_64_after_hwframe+0x6e/0x76 > > > Signed-off-by: Hou Tao > --- > kernel/bpf/helpers.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 56b0c1f678ee7..f43038931935e 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -32,12 +32,13 @@ > * > * Different map implementations will rely on rcu in map methods > * lookup/update/delete, therefore eBPF programs must run under rcu lock > - * if program is allowed to access maps, so check rcu_read_lock_held in > - * all three functions. > + * if program is allowed to access maps, so check rcu_read_lock_held() or > + * rcu_read_lock_trace_held() in all three functions. > */ > BPF_CALL_2(bpf_map_lookup_elem, struct bpf_map *, map, void *, key) > { > - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); > + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && > + !rcu_read_lock_bh_held()); > return (unsigned long) map->ops->map_lookup_elem(map, key); > } > > @@ -53,7 +54,8 @@ const struct bpf_func_proto bpf_map_lookup_elem_proto = { > BPF_CALL_4(bpf_map_update_elem, struct bpf_map *, map, void *, key, > void *, value, u64, flags) > { > - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); > + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && > + !rcu_read_lock_bh_held()); > return map->ops->map_update_elem(map, key, value, flags); > } > > @@ -70,7 +72,8 @@ const struct bpf_func_proto bpf_map_update_elem_proto = { > > BPF_CALL_2(bpf_map_delete_elem, struct bpf_map *, map, void *, key) > { > - WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_bh_held()); > + WARN_ON_ONCE(!rcu_read_lock_held() && !rcu_read_lock_trace_held() && > + !rcu_read_lock_bh_held()); Should these WARN_ON_ONCE be removed from the helpers instead? For catching error purpose, the ops->map_{lookup,update,delete}_elem are inlined for the jitted case which I believe is the bpf-CI setting also. Meaning the above change won't help to catch error in the common normal case. > return map->ops->map_delete_elem(map, key); > } >