Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt

From: Ilya Maximets <i.maximets@ovn.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Ilya Maximets <i.maximets@ovn.org>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S . Miller" <davem@davemloft.net>,
	Jonathan Lemon <jonathan.lemon@gmail.com>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt
Date: Sun, 13 Oct 2019 12:17:47 +0200	[thread overview]
Message-ID: <c338b2fd-8e0d-885d-5895-317d20800815@ovn.org> (raw)
In-Reply-To: <20191012232437.2xpi5mmmv7mxz3yy@ast-mbp.dhcp.thefacebook.com>

On 13.10.2019 1:24, Alexei Starovoitov wrote:
> On Wed, Oct 09, 2019 at 06:49:29PM +0200, Ilya Maximets wrote:
>> 'struct xdp_umem_reg' has 4 bytes of padding at the end that makes
>> valgrind complain about passing uninitialized stack memory to the
>> syscall:
>>
>>    Syscall param socketcall.setsockopt() points to uninitialised byte(s)
>>      at 0x4E7AB7E: setsockopt (in /usr/lib64/libc-2.29.so)
>>      by 0x4BDE035: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:172)
>>    Uninitialised value was created by a stack allocation
>>      at 0x4BDDEBA: xsk_umem__create@@LIBBPF_0.0.4 (xsk.c:140)
>>
>> Padding bytes appeared after introducing of a new 'flags' field.
>> memset() is required to clear them.
>>
>> Fixes: 10d30e301732 ("libbpf: add flags to umem config")
>> Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
>> ---
>>
>> Version 2:
>>    * Struct initializer replaced with explicit memset(). [Andrii]
>>
>>   tools/lib/bpf/xsk.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
>> index a902838f9fcc..9d5348086203 100644
>> --- a/tools/lib/bpf/xsk.c
>> +++ b/tools/lib/bpf/xsk.c
>> @@ -163,6 +163,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area,
>>   	umem->umem_area = umem_area;
>>   	xsk_set_umem_config(&umem->config, usr_config);
>>   
>> +	memset(&mr, 0, sizeof(mr));
>>   	mr.addr = (uintptr_t)umem_area;
>>   	mr.len = size;
>>   	mr.chunk_size = umem->config.frame_size;
> 
> This was already applied. Why did you resend?
> 

Sorry, it wasn't me.  Looking at the mail delivery chain:

There is some strange server listssympa-test.colorado.edu.
Looks like someone in colorado.edu is testing stuff on production server.

The simplified delivery chain looks like this:

Me -> relay6-d.mail.gandi.net -> vger.kernel.org -> mx.colorado.edu ->
mail.protection.outlook.com -> namprd03.prod.outlook.com ->
listssympa-test.colorado.edu -> spool.mail.gandi.net -> Me again!

Best regards, Ilya Maximets.