On 09.10.2019 18:29, Andrii Nakryiko wrote:
On Wed, Oct 9, 2019 at 8:43 AM Ilya Maximets <i.maximets@xxxxxxx> 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. Fixes: 10d30e301732 ("libbpf: add flags to umem config") Signed-off-by: Ilya Maximets <i.maximets@xxxxxxx> --- tools/lib/bpf/xsk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c index a902838f9fcc..26d9db783560 100644 --- a/tools/lib/bpf/xsk.c +++ b/tools/lib/bpf/xsk.c @@ -139,7 +139,7 @@ int xsk_umem__create_v0_0_4(struct xsk_umem **umem_ptr, void *umem_area, const struct xsk_umem_config *usr_config) { struct xdp_mmap_offsets off; - struct xdp_umem_reg mr; + struct xdp_umem_reg mr = {};well, guess what, even with this explicit initialization, padding is not guaranteed to be initialized (and it's sometimes is not in practice, I ran into such problems), only since C11 standard it is specified that padding is also zero-initialized. You have to do memset to 0.
OK. Sure. I'll send v2.
struct xsk_umem *umem; socklen_t optlen; void *map; -- 2.17.1
