[PATCH bpf-next 3/8] bpf: Disallow !call_get_func_ip progs tail-calling call_get_func_ip progs

[Leon Hwang]

Trampoline-based tracing programs that call bpf_get_func_ip() rely on
func_ip stored on stack. Mixing them with tracing programs that do not
share this requirement creates asymmetric expectations in tail calls.

Reject the combination of !call_get_func_ip progs with call_get_func_ip
progs in __bpf_prog_map_compatible() to address the issue.

Fixes: 1e37392cccde ("bpf: Enable BPF_TRAMP_F_IP_ARG for trampolines with 
call_get_func_ip")
Signed-off-by: Leon Hwang <leon.hw...@linux.dev>
---
 include/linux/bpf.h | 3 ++-
 kernel/bpf/core.c   | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2a2f6448a5fb..65793fd146c5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -288,7 +288,8 @@ struct bpf_map_owner {
        u32 jited:1,
            xdp_has_frags:1,
            sleepable:1,
-           kprobe_write_ctx:1;
+           kprobe_write_ctx:1,
+           call_get_func_ip:1;
        u64 storage_cookie[MAX_BPF_CGROUP_STORAGE_TYPE];
        const struct btf_type *attach_func_proto;
        enum bpf_attach_type expected_attach_type;
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index f99a901b5e48..01fce3fba0be 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2403,6 +2403,7 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map,
                map->owner->xdp_has_frags = aux->xdp_has_frags;
                map->owner->sleepable = fp->sleepable;
                map->owner->kprobe_write_ctx = aux->kprobe_write_ctx;
+               map->owner->call_get_func_ip = fp->call_get_func_ip;
                map->owner->expected_attach_type = fp->expected_attach_type;
                map->owner->attach_func_proto = aux->attach_func_proto;
                for_each_cgroup_storage_type(i) {
@@ -2418,6 +2419,9 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map,
                      map->owner->sleepable == fp->sleepable;
                if (ret && (!map->owner->kprobe_write_ctx && 
aux->kprobe_write_ctx))
                        ret = false;
+               if (ret && (!map->owner->call_get_func_ip && 
fp->call_get_func_ip &&
+                           prog_type == BPF_PROG_TYPE_TRACING))
+                       ret = false;
                if (ret &&
                    map->map_type == BPF_MAP_TYPE_PROG_ARRAY &&
                    map->owner->expected_attach_type != 
fp->expected_attach_type)
-- 
2.52.0