From a19a62e56478ba4afadfa7df94d0819542b7ccf8 Mon Sep 17 00:00:00 2001 From: Jesper Dangaard Brouer Date: Wed, 1 Feb 2023 18:31:55 +0100 Subject: [PATCH] selftests/bpf: xdp_hw_metadata cleanup cause segfault Using xdp_hw_metadata I experince Segmentation fault after seeing "detaching bpf program....". On my system the segfault happened when accessing bpf_obj->skeleton in xdp_hw_metadata__destroy(bpf_obj) call. That doesn't make any sense as this memory have not been freed by program at this point in time. Prior to calling xdp_hw_metadata__destroy(bpf_obj) the function close_xsk() is called for each RX-queue xsk. The real bug lays in close_xsk() that unmap via munmap() the wrong memory pointer. The call xsk_umem__delete(xsk->umem) will free xsk->umem, thus the call to munmap(xsk->umem, UMEM_SIZE) will have unpredictable behavior. And man page explain subsequent references to these pages will generate SIGSEGV. Unmapping xsk->umem_area instead removes the segfault. Fixes: 297a3f124155 ("selftests/bpf: Simple program to dump XDP RX metadata") Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann Acked-by: Stanislav Fomichev Link: https://lore.kernel.org/bpf/167527271533.937063.5717065138099679142.stgit@firesoul --- tools/testing/selftests/bpf/xdp_hw_metadata.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c index 3823b1c..438083e3 100644 --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c @@ -121,7 +121,7 @@ static void close_xsk(struct xsk *xsk) xsk_umem__delete(xsk->umem); if (xsk->socket) xsk_socket__delete(xsk->socket); - munmap(xsk->umem, UMEM_SIZE); + munmap(xsk->umem_area, UMEM_SIZE); } static void refill_rx(struct xsk *xsk, __u64 addr) -- 2.7.4