From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Eduard Zingerman <eddyz87@gmail.com>,
Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Amery Hung <ameryhung@gmail.com>,
Emil Tsalapatis <emil@etsalapatis.com>,
Nicholas Carlini <npc@anthropic.com>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: [PATCH bpf-next v2 10/11] bpf: Scope the bpf_for_each_map_elem() array key to the callback frame
Date: Fri, 9 Oct 2026 13:27:57 -0700 [thread overview]
Message-ID: <20261009202759.50520-11-ihor.solodrai@linux.dev> (raw)
In-Reply-To: <20261009202759.50520-1-ihor.solodrai@linux.dev>
bpf_for_each_map_elem() passes array and per-CPU array callbacks the
address of a key on the helper's stack.
A callback can save that pointer in its context and dereference it
after the helper returns. Loads through PTR_TO_MAP_KEY are not
fault-protected, allowing a four-byte read-only leak of reused kernel
stack.
The verifier tracks the pointer's type and key size, but does not tie
its lifetime to the callback invocation.
Anchor R2 to a frame reference in the array map callback setup so the
key and its copies are invalidated on callback return. Leave hash keys
and map values unchanged, since their storage is not callback-local.
Reported-by: Nicholas Carlini <npc@anthropic.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
kernel/bpf/arraymap.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 0fe9afd4a591..5e8669e311b6 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -855,6 +855,20 @@ static u64 array_map_mem_usage(const struct bpf_map *map)
return usage;
}
+static int array_map_set_for_each_callback_args(struct bpf_verifier_env *env,
+ struct bpf_verifier_state *state,
+ struct bpf_func_state *caller,
+ struct bpf_func_state *callee)
+{
+ int err;
+
+ err = map_set_for_each_callback_args(env, state, caller, callee);
+ if (err)
+ return err;
+
+ return mark_frame_scoped_arg(env, state, callee, BPF_REG_2);
+}
+
BTF_ID_LIST_SINGLE(array_map_btf_ids, struct, bpf_array)
const struct bpf_map_ops array_map_ops = {
.map_meta_equal = array_map_meta_equal,
@@ -875,7 +889,7 @@ const struct bpf_map_ops array_map_ops = {
.map_check_btf = array_map_check_btf,
.map_lookup_batch = generic_map_lookup_batch,
.map_update_batch = generic_map_update_batch,
- .map_set_for_each_callback_args = map_set_for_each_callback_args,
+ .map_set_for_each_callback_args = array_map_set_for_each_callback_args,
.map_for_each_callback = bpf_for_each_array_elem,
.map_mem_usage = array_map_mem_usage,
.map_btf_id = &array_map_btf_ids[0],
@@ -900,7 +914,7 @@ const struct bpf_map_ops percpu_array_map_ops = {
.map_check_btf = array_map_check_btf,
.map_lookup_batch = generic_map_lookup_batch,
.map_update_batch = generic_map_update_batch,
- .map_set_for_each_callback_args = map_set_for_each_callback_args,
+ .map_set_for_each_callback_args = array_map_set_for_each_callback_args,
.map_for_each_callback = bpf_for_each_array_elem,
.map_mem_usage = array_map_mem_usage,
.map_btf_id = &array_map_btf_ids[0],
--
2.56.0
next prev parent reply other threads:[~2026-10-09 20:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-09 20:27 [PATCH bpf-next v2 00/11] bpf: Scope callback arguments to their frame Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 01/11] bpf: Set up callee state outside of setup_func_entry() Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 02/11] bpf: Pass the owning verifier state to callback setters Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 03/11] bpf: Append complete reference states Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 04/11] bpf: Separate reference removal from descendant invalidation Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 05/11] bpf: Share map-backed callback register setup Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 06/11] bpf: Rely on callback frame initialization defaults Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 07/11] bpf: Introduce REF_TYPE_FRAME in the verifier Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 08/11] bpf: Scope the bpf_user_ringbuf_drain() dynptr to its callback frame Ihor Solodrai
2026-10-09 20:27 ` [PATCH bpf-next v2 09/11] selftests/bpf: Cover the user ringbuf callback dynptr lifetime Ihor Solodrai
2026-10-09 20:27 ` Ihor Solodrai [this message]
2026-10-09 20:27 ` [PATCH bpf-next v2 11/11] selftests/bpf: Cover callback-frame map key lifetime Ihor Solodrai
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