diff options
| author | Alexei Starovoitov <ast@kernel.org> | 2023-04-20 18:49:01 -0700 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-04-21 16:27:56 +0200 |
| commit | acf1c3d68e9a31f10d92bc67ad4673cdae5e8d92 (patch) | |
| tree | 63a126a226bb5d1f99550916f93f85a2029dacec /kernel/bpf/btf.c | |
| parent | 267a6e4e7870beb8896c192da175800e47c82407 (diff) | |
bpf: Fix race between btf_put and btf_idr walk.
Florian and Eduard reported hard dead lock:
[ 58.433327] _raw_spin_lock_irqsave+0x40/0x50
[ 58.433334] btf_put+0x43/0x90
[ 58.433338] bpf_find_btf_id+0x157/0x240
[ 58.433353] btf_parse_fields+0x921/0x11c0
This happens since btf->refcount can be 1 at the time of btf_put() and
btf_put() will call btf_free_id() which will try to grab btf_idr_lock
and will dead lock.
Avoid the issue by doing btf_put() without locking.
Fixes: 3d78417b60fb ("bpf: Add bpf_btf_find_by_name_kind() helper.")
Fixes: 1e89106da253 ("bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn().")
Reported-by: Florian Westphal <fw@strlen.de>
Reported-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20230421014901.70908-1-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf/btf.c')
| -rw-r--r-- | kernel/bpf/btf.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index a0887ee44e89..7db4ec125fbd 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -577,8 +577,8 @@ static s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) *btf_p = btf; return ret; } - spin_lock_bh(&btf_idr_lock); btf_put(btf); + spin_lock_bh(&btf_idr_lock); } spin_unlock_bh(&btf_idr_lock); return ret; @@ -8354,12 +8354,10 @@ check_modules: btf_get(mod_btf); spin_unlock_bh(&btf_idr_lock); cands = bpf_core_add_cands(cands, mod_btf, btf_nr_types(main_btf)); - if (IS_ERR(cands)) { - btf_put(mod_btf); + btf_put(mod_btf); + if (IS_ERR(cands)) return ERR_CAST(cands); - } spin_lock_bh(&btf_idr_lock); - btf_put(mod_btf); } spin_unlock_bh(&btf_idr_lock); /* cands is a pointer to kmalloced memory here if cands->cnt > 0 |