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authorAndrii Nakryiko <andrii@kernel.org>2023-02-16 05:59:52 +0100
committerDaniel Borkmann <daniel@iogearbox.net>2023-02-17 21:20:44 +0100
commitd384dce281ed1b504fae2e279507827638d56fa3 (patch)
tree18dd9f650dca039d06f89a28977c950a06a4404e /kernel/bpf
parentLoongArch, bpf: Use 4 instructions for function address in JIT (diff)
downloadlinux-d384dce281ed1b504fae2e279507827638d56fa3.tar.xz
linux-d384dce281ed1b504fae2e279507827638d56fa3.zip
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/bpf')
-rw-r--r--kernel/bpf/btf.c13
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;
}