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bpf_redirect_map not working after tail call
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Sebastiano Miano
Dear all,
We have noticed that the bpf_redirect_map returns an error when it is called after a tail call. The xdp_redirect_map program (under sample/bpf) works fine, but if we modify it as shown in the following diff, it doesn't work anymore. I have debugged it with the xdp_monitor application and the error returned is EFAULT. Is this a known issue? Am I doing something wrong? Thanks, Sebastiano P.S. I have tested the program with the latest bpf-next kernel. ------------ diff --git a/samples/bpf/xdp_redirect_map_kern.c b/samples/bpf/xdp_redirect_map_kern.c index 740a529..bf1275a 100644 --- a/samples/bpf/xdp_redirect_map_kern.c +++ b/samples/bpf/xdp_redirect_map_kern.c @@ -36,6 +36,13 @@ struct bpf_map_def SEC("maps") rxcnt = { .max_entries = 1, }; +struct bpf_map_def SEC("maps") prog_table = { + .type = BPF_MAP_TYPE_PROG_ARRAY, + .key_size = sizeof(int), + .value_size = sizeof(int), + .max_entries = 32, +}; + static void swap_src_dst_mac(void *data) { unsigned short *p = data; @@ -89,4 +96,15 @@ int xdp_redirect_dummy_prog(struct xdp_md *ctx) return XDP_PASS; } +/* Entry point */ +SEC("xdp_redirect_entry_point") +int xdp_redirect_entry_point_prog(struct xdp_md *ctx) +{ + //char fmt[] = "xdp_redirect_entry_point\n"; + //bpf_trace_printk(fmt, sizeof(fmt)); + bpf_tail_call(ctx, &prog_table, 0); + // Tail call failed + return XDP_DROP; +} + char _license[] SEC("license") = "GPL"; diff --git a/samples/bpf/xdp_redirect_map_user.c b/samples/bpf/xdp_redirect_map_user.c index 4445e76..b2d2059 100644 --- a/samples/bpf/xdp_redirect_map_user.c +++ b/samples/bpf/xdp_redirect_map_user.c @@ -120,7 +120,13 @@ int main(int argc, char **argv) return 1; } - if (bpf_set_link_xdp_fd(ifindex_in, prog_fd[0], xdp_flags) < 0) { + ret = bpf_map_update_elem(map_fd[2], &key, &prog_fd[0], 0); + if (ret) { + perror("bpf_update_elem"); + goto out; + } + + if (bpf_set_link_xdp_fd(ifindex_in, prog_fd[2], xdp_flags) < 0) { printf("ERROR: link set xdp fd failed on %d\n", ifindex_in); return 1; } |
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On Fri, 1 Jun 2018 14:15:58 +0200
Sebastiano Miano via iovisor-dev <iovisor-dev@...> wrote: Dear all,Argh, this is likely an issue/bug due to the check xdp_map_invalid(), that was introduced in commit 7c3001313396 ("bpf: fix ri->map_owner pointer on bpf_prog_realloc"). To Daniel, I don't know how to solve this, could you give some advice? static inline bool xdp_map_invalid(const struct bpf_prog *xdp_prog, unsigned long aux) { return (unsigned long)xdp_prog->aux != aux; } static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, struct bpf_prog *xdp_prog) { struct redirect_info *ri = this_cpu_ptr(&redirect_info); unsigned long map_owner = ri->map_owner; struct bpf_map *map = ri->map; u32 index = ri->ifindex; void *fwd = NULL; int err; [...] if (unlikely(xdp_map_invalid(xdp_prog, map_owner))) { err = -EFAULT; map = NULL; goto err; } [...] P.S. I have tested the program with the latest bpf-next kernel. -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer |
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Daniel Borkmann
On 06/04/2018 01:04 PM, Jesper Dangaard Brouer via iovisor-dev wrote:
On Fri, 1 Jun 2018 14:15:58 +0200Argh, I see the issue. Working on a fix after checking the syzkaller reports. Thanks for the report! |
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