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

[Ilya Maximets]

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@xxxxxxx>
> > ---
> >
> > 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:

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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:

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Best regards, Ilya Maximets.