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libbpf: fix attach of prog with multiple sections 

When BPF programs which consists of multiple executable sections via
iproute2+libbpf (configured with LIBBPF_FORCE=on), we noticed that a
wrong section can be attached to a device. E.g.:

    # tc qdisc replace dev lxc_health clsact
    # tc filter replace dev lxc_health ingress prio 1 \
        handle 1 bpf da obj bpf_lxc.o sec from-container
    # tc filter show dev lxc_health ingress filter protocol all
        pref 1 bpf chain 0 filter protocol all pref 1 bpf chain 0
        handle 0x1 bpf_lxc.o:[__send_drop_notify] <-- WRONG SECTION
        direct-action not_in_hw id 38 tag 7d891814eda6809e jited

After taking a closer look into load_bpf_object() in lib/bpf_libbpf.c,
we noticed that the filter used in the program iterator does not check
whether a program section name matches a requested section name
(cfg->section). This can lead to a wrong prog FD being used to attach
the program.

Fixes: 6d61a2b557 ("lib: add libbpf support")
Signed-off-by: Martynas Pumputis <m@lambda.lt>
Acked-by: Hangbin Liu <haliu@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
This commit is contained in:
Martynas Pumputis 2021-07-05 14:43:07 +02:00 committed by Stephen Hemminger
parent 02c06ffc13
commit 83d4d61bc9
1 changed files with 6 additions and 3 deletions
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9
lib/bpf_libbpf.c
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@ -268,10 +268,12 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
}
bpf_object__for_each_program(p, obj) {
bool prog_to_attach = !prog && cfg->section &&
!strcmp(get_bpf_program__section_name(p), cfg->section);
/* Only load the programs that will either be subsequently
* attached or inserted into a tail call map */
if (find_legacy_tail_calls(p, obj) < 0 && cfg->section &&
strcmp(get_bpf_program__section_name(p), cfg->section)) {
if (find_legacy_tail_calls(p, obj) < 0 && !prog_to_attach) {
ret = bpf_program__set_autoload(p, false);
if (ret)
return -EINVAL;
@ -280,7 +282,8 @@ static int load_bpf_object(struct bpf_cfg_in *cfg)
bpf_program__set_type(p, cfg->type);
bpf_program__set_ifindex(p, cfg->ifindex);
if (!prog)
if (prog_to_attach)
prog = p;
}