diff options
| author | Andrii Nakryiko <andrii@kernel.org> | 2023-02-16 07:59:52 +0300 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-02-17 23:20:44 +0300 |
| commit | d384dce281ed1b504fae2e279507827638d56fa3 (patch) | |
| tree | 18dd9f650dca039d06f89a28977c950a06a4404e /kernel | |
| parent | 64f50f6575721ef03d001e907455cbe3baa2a5b1 (diff) | |
| download | linux-d384dce281ed1b504fae2e279507827638d56fa3.tar.xz | |
bpf: Fix global subprog context argument resolution logic
KPROBE program's user-facing context type is defined as typedef
bpf_user_pt_regs_t. This leads to a problem when trying to passing
kprobe/uprobe/usdt context argument into global subprog, as kernel
always strip away mods and typedefs of user-supplied type, but takes
expected type from bpf_ctx_convert as is, which causes mismatch.
Current way to work around this is to define a fake struct with the same
name as expected typedef:
struct bpf_user_pt_regs_t {};
__noinline my_global_subprog(struct bpf_user_pt_regs_t *ctx) { ... }
This patch fixes the issue by resolving expected type, if it's not
a struct. It still leaves the above work-around working for backwards
compatibility.
Fixes: 91cc1a99740e ("bpf: Annotate context types")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230216045954.3002473-2-andrii@kernel.org
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/btf.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 6582735ef1fc..fa22ec79ac0e 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5669,6 +5669,7 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf, if (!ctx_struct) /* should not happen */ return NULL; +again: ctx_tname = btf_name_by_offset(btf_vmlinux, ctx_struct->name_off); if (!ctx_tname) { /* should not happen */ @@ -5682,8 +5683,16 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf, * int socket_filter_bpf_prog(struct __sk_buff *skb) * { // no fields of skb are ever used } */ - if (strcmp(ctx_tname, tname)) - return NULL; + if (strcmp(ctx_tname, tname)) { + /* bpf_user_pt_regs_t is a typedef, so resolve it to + * underlying struct and check name again + */ + if (!btf_type_is_modifier(ctx_struct)) + return NULL; + while (btf_type_is_modifier(ctx_struct)) + ctx_struct = btf_type_by_id(btf_vmlinux, ctx_struct->type); + goto again; + } return ctx_type; } |