[PATCH bpf-next 2/8] bpf: Disallow !kprobe_write_ctx progs tail-calling kprobe_write_ctx progs
From: Leon Hwang <hidden>
Date: 2026-02-24 15:41:49
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
uprobe programs that can modify pt_regs require different runtime
assumptions than pt_regs-read-only uprobe programs. Mixing both in
one prog_array can make owner expectations diverge from callee behavior.
Reject the combination of !kprobe_write_ctx progs with kprobe_write_ctx
progs in __bpf_prog_map_compatible() to address the issue.
Fixes: 7384893d970e ("bpf: Allow uprobe program to change context registers")
Signed-off-by: Leon Hwang <redacted>
---
include/linux/bpf.h | 7 ++++---
kernel/bpf/core.c | 3 +++
2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b78b53198a2e..2a2f6448a5fb 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h@@ -285,9 +285,10 @@ struct bpf_list_node_kern { */ struct bpf_map_owner { enum bpf_prog_type type; - bool jited; - bool xdp_has_frags; - bool sleepable; + u32 jited:1, + xdp_has_frags:1, + sleepable:1, + kprobe_write_ctx: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 3ece2da55625..f99a901b5e48 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c@@ -2402,6 +2402,7 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map, map->owner->jited = fp->jited; 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->expected_attach_type = fp->expected_attach_type; map->owner->attach_func_proto = aux->attach_func_proto; for_each_cgroup_storage_type(i) {
@@ -2415,6 +2416,8 @@ static bool __bpf_prog_map_compatible(struct bpf_map *map, map->owner->jited == fp->jited && map->owner->xdp_has_frags == aux->xdp_has_frags && map->owner->sleepable == fp->sleepable; + if (ret && (!map->owner->kprobe_write_ctx && aux->kprobe_write_ctx)) + ret = false; if (ret && map->map_type == BPF_MAP_TYPE_PROG_ARRAY && map->owner->expected_attach_type != fp->expected_attach_type)
--
2.52.0