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Miller" , Jonathan Lemon , Andrii Nakryiko Subject: Re: [PATCH bpf v2] libbpf: fix passing uninitialized bytes to setsockopt Message-ID: <20191012232437.2xpi5mmmv7mxz3yy@ast-mbp.dhcp.thefacebook.com> References: <5da24d48.1c69fb81.a3069.c817SMTPIN_ADDED_BROKEN@mx.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5da24d48.1c69fb81.a3069.c817SMTPIN_ADDED_BROKEN@mx.google.com> User-Agent: NeoMutt/20180223 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 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 > --- > > 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?