For program types that don't have named context type name (e.g., BPF
iterator programs or tracepoint programs), ctx_tname will be a non-NULL
empty string. For such programs it shouldn't be possible to have
PTR_TO_CTX argument for global subprogs based on type name alone.
arg:ctx tag is the only way to have PTR_TO_CTX passed into global
subprog for such program types.
Fix this loop hole, which currently would assume PTR_TO_CTX whenever
user uses a pointer to anonymous struct as an argument to their global
subprogs. This happens in practice with the following (quite common, in
practice) approach:
typedef struct { /* anonymous */
int x;
} my_type_t;
int my_subprog(my_type_t *arg) { ... }
User's intent is to have PTR_TO_MEM argument for `arg`, but verifier
will complain about expecting PTR_TO_CTX.
Fixes: 91cc1a99740e ("bpf: Annotate context types")
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
kernel/bpf/btf.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 8e06d29961f1..d6021290caba 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5725,6 +5725,9 @@ btf_get_prog_ctx_type(struct bpf_verifier_log *log, const struct btf *btf,
bpf_log(log, "Please fix kernel include/linux/bpf_types.h\n");
return NULL;
}
+ /* program types without named context types work only with arg:ctx tag */
+ if (ctx_tname[0] == '\0')
+ return NULL;
/* only compare that prog's ctx type name is the same as
* kernel expects. No need to compare field by field.
* It's ok for bpf prog to do:
--
2.39.3
