Commit 25bfef43 authored Oct 09, 2019 by Ilya Maximets Committed by Alexei Starovoitov Oct 09, 2019

libbpf: Fix passing uninitialized bytes to setsockopt



'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: 10d30e30 ("libbpf: add flags to umem config")
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191009164929.17242-1-i.maximets@ovn.org

parent f1177102

tools/lib/bpf/xsk.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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;

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