diff options
| author | Ning Ding <dingning04@gmail.com> | 2026-08-03 04:26:08 -0700 |
|---|---|---|
| committer | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2026-08-04 11:33:56 +0200 |
| commit | 180c7000712db77063b3a26f4c97e7dd9038f449 (patch) | |
| tree | b30b1713af1939421ebec26796710b75ccbc1e18 /kernel | |
| parent | 457d4ecb47aaf7a2cb46aaadd76e8c812e4f3c9e (diff) | |
bpf: Invalidate RCU pointers after final spin unlock
In a sleepable BPF program, a spin lock can provide the only RCU protection
for a kptr. The final bpf_spin_unlock() ends that protection, but the
verifier leaves the pointer valid. Another CPU can then free the object
before the pointer is used. A capability-limited runtime PoC triggered a
task_struct use-after-free in __bpf_get_task_stack().
Record whether the program is in an RCU-protected context before releasing
the lock. Invalidate RCU-protected pointers only when the unlock leaves the
final such context. This preserves valid pointers in non-sleepable programs
and inside an explicit RCU read-side section.
Fixes: 5861d1e8dbc4 ("bpf: Allow bpf_spin_{lock,unlock} in sleepable progs")
Assisted-by: Codex:gpt-5.6-sol
Assisted-by: ChatGPT:GPT-5.6-Pro
Signed-off-by: Ning Ding <dingning04@gmail.com>
Link: https://lore.kernel.org/bpf/20260803112615.3362122-2-dingning04@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b274004fccfd..7439afdc851a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -206,6 +206,7 @@ static int acquire_reference(struct bpf_verifier_env *env, int insn_idx, int par static int release_reference_nomark(struct bpf_verifier_state *state, int id); static int release_reference(struct bpf_verifier_env *env, int id); static void invalidate_non_owning_refs(struct bpf_verifier_env *env); +static void invalidate_rcu_protected_refs(struct bpf_verifier_env *env); static bool in_rbtree_lock_required_cb(struct bpf_verifier_env *env); static bool is_tracing_prog_type(enum bpf_prog_type type); static int ref_set_non_owning(struct bpf_verifier_env *env, @@ -7165,6 +7166,7 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state return err; } } else { + bool was_in_rcu_cs; void *ptr; int type; @@ -7192,10 +7194,13 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state verbose(env, "%s_unlock cannot be out of order\n", lock_str); return -EINVAL; } + was_in_rcu_cs = in_rcu_cs(env); if (release_lock_state(cur, type, reg->id, ptr)) { verbose(env, "%s_unlock of different lock\n", lock_str); return -EINVAL; } + if (was_in_rcu_cs && !in_rcu_cs(env)) + invalidate_rcu_protected_refs(env); invalidate_non_owning_refs(env); } |