diff options
| author | Yuan Chen <chenyuan@kylinos.cn> | 2026-09-24 10:37:36 +0800 |
|---|---|---|
| committer | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2026-09-24 10:50:17 +0200 |
| commit | c43c348a84460b003fa757dd43d8c89848ae220d (patch) | |
| tree | 3ee6516be2ed5e86cd94a631e6aff8c265ceede2 /include/linux | |
| parent | 24629aac43d2884109ae47a993fd51b504e2b09b (diff) | |
bpf: Keep target extended until its last freplace link detaches
The is_extended / prog_array_member_cnt protocol introduced by commit
d6083f040d5d ("bpf: Prevent tailcall infinite loop caused by freplace")
keeps a prog extended by a freplace program out of prog_array maps, and
vice versa: once a tail call re-enters an extended subprogram, its
tail_call_cnt resets on every execution and the loop never terminates.
But is_extended is a plain boolean, while one target prog can carry
several freplace links at the same time, one on its entry and one on a
global subprogram. __bpf_trampoline_unlink_prog() cleared is_extended
whenever *any* freplace link detached, so detaching one of two links
re-armed the unbounded loop through the remaining one.
Replace the is_extended boolean with a count of the freplace links
attached to each target prog, so the target stays extended until its
last link detaches. Also rename bpf_freplace_check_tgt_prog() to
bpf_freplace_link_tgt_prog(), as the helper has never been a pure
check: it reserves the target prog on success.
Fixes: d6083f040d5d ("bpf: Prevent tailcall infinite loop caused by freplace")
Signed-off-by: Yuan Chen <chenyuan@kylinos.cn>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20260924023737.1140521-2-chenyuan_fl@163.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/bpf.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 9525d3ecd923..1e1ce2afe2ed 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1833,7 +1833,6 @@ struct bpf_prog_aux { bool xdp_has_frags; bool exception_cb; bool exception_boundary; - bool is_extended; /* true if extended by freplace program */ bool jits_use_priv_stack; bool priv_stack_requested; bool changes_pkt_data; @@ -1845,7 +1844,7 @@ struct bpf_prog_aux { u8 verdict; } sig; u64 prog_array_member_cnt; /* counts how many times as member of prog_array */ - struct mutex ext_mutex; /* mutex for is_extended and prog_array_member_cnt */ + struct mutex ext_mutex; /* mutex for freplace_link_cnt and prog_array_member_cnt */ struct bpf_arena *arena; void (*recursion_detected)(struct bpf_prog *prog); /* callback if recursion is detected */ /* BTF_KIND_FUNC_PROTO for valid attach_btf_id */ @@ -1877,6 +1876,7 @@ struct bpf_prog_aux { char name[BPF_OBJ_NAME_LEN]; u64 (*bpf_exception_cb)(u64 cookie, u64 sp, u64 bp, u64, u64); u16 stack_arg_sp_adjust; + u16 freplace_link_cnt; /* counts freplace links extending this prog */ #ifdef CONFIG_SECURITY void *security; #endif |