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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id h21sm17302774pfc.118.2021.09.27.11.27.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Sep 2021 11:27:02 -0700 (PDT) From: Kees Cook To: Alexei Starovoitov Cc: Kees Cook , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, "Gustavo A . R . Silva" , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH 2/2] bpf: Replace callers of BPF_CAST_CALL with proper function typedef Date: Mon, 27 Sep 2021 11:27:00 -0700 Message-Id: <20210927182700.2980499-3-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210927182700.2980499-1-keescook@chromium.org> References: <20210927182700.2980499-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5714; h=from:subject; bh=9JNJGH2jsdZr2e7yM2qvfQSMdoLIKPava0PYTFnVOoE=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhUgzzQWvlA6xROER3rNkckjnSKXUmUWAhnSt0wEvb X2wRni2JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYVIM8wAKCRCJcvTf3G3AJl+zD/ 4kSHS8ROEmGLh19XUw5x0ZU+DiRLH2SQ1oI6znQZbgydbJmDS81IMLn+XMiTZevkXONslNzNQKTH1c kc3SDmSLlCifVvC0QCFUi6hajHSbBdLJHYTFTrqCAesvGCtZOne84ZyN5VGs0A0nNrodSE3okF+YDV rN5lLXMpOXS5Wnn+xs1RjKavvL9g1WkOlDAMe0P7IoPumksdGo/xHx17i7qpiqGx8uF5CbhHhyZkyn 6ri6k3O2cOOwGiZKP3nu/BFMBu8648kDEnA8aVTx/cGWLGyVg5wnVFxdEXtXpB5Y9+LlwOkVEvPlAh OufsAAX36wtfReKPXEDrO8eLq/513snXaFKkvKK7AuzDqmGefSlj4I+WDofkWJzHvr3yzS0bKoAoMW bMVA7nsYELnyydbt7/UZFwdb+ZIvqgK200kmEkNkOJjAy6mAb5IED7982+JUMxiNIZd/vHZNtIiB98 urArKjnn5jRgxZMyJw/g7zk6nbLJt9i0Nd2zXn53sWNM0CiVewTUkEFnSHlrOIEPJXeEUOTBYuezaB cwEdmdM8XpOacyGM52zWM87QBpxT5/2nbFiuQJhnpIx4DkEpld9a1Pg8ElZyv+lVE5G1SU2SaaMFrc 3DN/n+3XaZDNpjq3aM9MCTbmZY6KvpV2m6gAf3HtFeQscEWax6MhgkyQpasg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org In order to keep ahead of cases in the kernel where Control Flow Integrity (CFI) may trip over function call casts, enabling -Wcast-function-type is helpful. To that end, BPF_CAST_CALL causes various warnings and is one of the last places in the kernel triggering this warning. For actual function calls, replace BPF_CAST_CALL() with a typedef, which captures the same details about the given function pointers. This change results in no object code difference. Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Andrii Nakryiko Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: John Fastabend Cc: KP Singh Cc: netdev@vger.kernel.org Cc: bpf@vger.kernel.org Cc: Gustavo A. R. Silva Link: https://github.com/KSPP/linux/issues/20 Signed-off-by: Kees Cook --- include/linux/bpf.h | 4 +++- include/linux/filter.h | 5 ----- kernel/bpf/arraymap.c | 7 +++---- kernel/bpf/hashtab.c | 7 +++---- kernel/bpf/helpers.c | 5 ++--- 5 files changed, 11 insertions(+), 17 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f4c16f19f83e..ff633f08cb51 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -48,6 +48,7 @@ extern struct idr btf_idr; extern spinlock_t btf_idr_lock; extern struct kobject *btf_kobj; +typedef u64 (*bpf_callback_t)(u64, u64, u64, u64, u64); typedef int (*bpf_iter_init_seq_priv_t)(void *private_data, struct bpf_iter_aux_info *aux); typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data); @@ -142,7 +143,8 @@ struct bpf_map_ops { int (*map_set_for_each_callback_args)(struct bpf_verifier_env *env, struct bpf_func_state *caller, struct bpf_func_state *callee); - int (*map_for_each_callback)(struct bpf_map *map, void *callback_fn, + int (*map_for_each_callback)(struct bpf_map *map, + bpf_callback_t callback_fn, void *callback_ctx, u64 flags); /* BTF name and id of struct allocated by map_alloc */ diff --git a/include/linux/filter.h b/include/linux/filter.h index 6c247663d4ce..47f80adbe744 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -360,11 +360,6 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) .off = 0, \ .imm = TGT }) -/* Function call */ - -#define BPF_CAST_CALL(x) \ - ((u64 (*)(u64, u64, u64, u64, u64))(x)) - /* Convert function address to BPF immediate */ #define BPF_CALL_IMM(x) ((void *)(x) - (void *)__bpf_call_base) diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c index cebd4fb06d19..5e1ccfae916b 100644 --- a/kernel/bpf/arraymap.c +++ b/kernel/bpf/arraymap.c @@ -645,7 +645,7 @@ static const struct bpf_iter_seq_info iter_seq_info = { .seq_priv_size = sizeof(struct bpf_iter_seq_array_map_info), }; -static int bpf_for_each_array_elem(struct bpf_map *map, void *callback_fn, +static int bpf_for_each_array_elem(struct bpf_map *map, bpf_callback_t callback_fn, void *callback_ctx, u64 flags) { u32 i, key, num_elems = 0; @@ -668,9 +668,8 @@ static int bpf_for_each_array_elem(struct bpf_map *map, void *callback_fn, val = array->value + array->elem_size * i; num_elems++; key = i; - ret = BPF_CAST_CALL(callback_fn)((u64)(long)map, - (u64)(long)&key, (u64)(long)val, - (u64)(long)callback_ctx, 0); + ret = callback_fn((u64)(long)map, (u64)(long)&key, + (u64)(long)val, (u64)(long)callback_ctx, 0); /* return value: 0 - continue, 1 - stop and return */ if (ret) break; diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 3d8f9d6997d5..d29af9988f37 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -2049,7 +2049,7 @@ static const struct bpf_iter_seq_info iter_seq_info = { .seq_priv_size = sizeof(struct bpf_iter_seq_hash_map_info), }; -static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn, +static int bpf_for_each_hash_elem(struct bpf_map *map, bpf_callback_t callback_fn, void *callback_ctx, u64 flags) { struct bpf_htab *htab = container_of(map, struct bpf_htab, map); @@ -2089,9 +2089,8 @@ static int bpf_for_each_hash_elem(struct bpf_map *map, void *callback_fn, val = elem->key + roundup_key_size; } num_elems++; - ret = BPF_CAST_CALL(callback_fn)((u64)(long)map, - (u64)(long)key, (u64)(long)val, - (u64)(long)callback_ctx, 0); + ret = callback_fn((u64)(long)map, (u64)(long)key, + (u64)(long)val, (u64)(long)callback_ctx, 0); /* return value: 0 - continue, 1 - stop and return */ if (ret) { rcu_read_unlock(); diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 9aabf84afd4b..25d7e02ba449 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1058,7 +1058,7 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer) struct bpf_hrtimer *t = container_of(hrtimer, struct bpf_hrtimer, timer); struct bpf_map *map = t->map; void *value = t->value; - void *callback_fn; + bpf_callback_t callback_fn; void *key; u32 idx; @@ -1083,8 +1083,7 @@ static enum hrtimer_restart bpf_timer_cb(struct hrtimer *hrtimer) key = value - round_up(map->key_size, 8); } - BPF_CAST_CALL(callback_fn)((u64)(long)map, (u64)(long)key, - (u64)(long)value, 0, 0); + callback_fn((u64)(long)map, (u64)(long)key, (u64)(long)value, 0, 0); /* The verifier checked that return value is zero. */ this_cpu_write(hrtimer_running, NULL); -- 2.30.2