This is a note to let you know that I've just added the patch titled bpf: Fix global subprog context argument resolution logic to the 6.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-fix-global-subprog-context-argument-resolution-l.patch and it can be found in the queue-6.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 3f26a34f5b5a0fc9b988fa7ce9149a390295c5c6 Author: Andrii Nakryiko <andrii@xxxxxxxxxx> Date: Wed Feb 15 20:59:52 2023 -0800 bpf: Fix global subprog context argument resolution logic [ Upstream commit d384dce281ed1b504fae2e279507827638d56fa3 ] 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@xxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx> Link: https://lore.kernel.org/bpf/20230216045954.3002473-2-andrii@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b7017cae6fd1e..530e200fbc477 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -5573,6 +5573,7 @@ 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 */ @@ -5586,8 +5587,16 @@ 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; }