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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y13sm144694pjc.50.2021.09.28.16.09.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Sep 2021 16:09:51 -0700 (PDT) From: Kees Cook To: Alexei Starovoitov Cc: Kees Cook , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, "Gustavo A . R . Silva" , Andrii Nakryiko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH bpf-next v2 1/2] bpf: Replace "want address" users of BPF_CAST_CALL with BPF_CALL_IMM Date: Tue, 28 Sep 2021 16:09:45 -0700 Message-Id: <20210928230946.4062144-2-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210928230946.4062144-1-keescook@chromium.org> References: <20210928230946.4062144-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=6536; h=from:subject; bh=QTrb9yWbYK4FblFNy6JPUgIc30eI7Imex7fw41+XQMY=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhU6C6+HLjGARSHaQSRNNSYiyWy34WeYI5V1BijsnQ YI8AnC2JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYVOgugAKCRCJcvTf3G3AJisqD/ wKrle0RcrwFqdohNLv+VetOOZbiu0XT5jhRPmTkV6unaNGSilxLgyqhLN3XoEFYoAaIEXHgMPLeaT5 Sv+HuAmBq8I465O+fVB3LFhMZPkNGbhhOTVZ8c1mwYarmi3Cq2ysXuR48uY96DLSOb8W7JqEIYUbSO LwNMvjFH18rbZMtN3+cqg32jiPCT0RjFyJvB2Ou44UJkBfUtvCtyet+feX4e7GU1d8Ar4KnkCQf4F2 dBErTvFFBmpz93z5Obv6CP5Dc6vvUImoHw1aBpk1eQ9Z3zBc1+8xJ/EG20VHEB9xj72JqwW+G8v/8J wFEn90IxCn3Fll2p7IBdVyeDt2bhJpmCHPZ0UXPGIClE5kVMBVtUepTSb3fASCkJrTJX4YOC669dzV ql3y0Ui+DUuH192thwMqMtDdq5PztL3QoQ92nl1CBO3aVgGJgYSP4orzO3NkuxbeM65vX1H/2Fdfk+ rHHOk4O18E3VrT/F49ORrzC6sjM1CxgekNwla0Sc8yjGhPsuXh0EXCrLGEcVBTQLTwj3FjArqLQCt8 mxVa2XD98mGWhY8UU3m+OQ2f/6e09hjJXmSLixOhpcIbsxnTfA4HKYdULOzx6Kds63PDSHX7uZFD4q bc94e7gyTIltxhTPrRl6FaEPuqNvZwXDJhY5h2r8Iqoy/1Dlse8BcLqqDoBg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@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. Most places using BPF_CAST_CALL actually just want a void * to perform math on. It's not actually performing a call, so just use a different helper to get the void *, by way of the new BPF_CALL_IMM() helper, which can clean up a common copy/paste idiom as well. This change results in no object code difference. Cc: Alexei Starovoitov Cc: Daniel Borkmann 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 Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/lkml/CAEf4Bzb46=-J5Fxc3mMZ8JQPtK1uoE0q6+g6WPz53Cvx=CBEhw@mail.gmail.com Reviewed-by: Gustavo A. R. Silva --- include/linux/filter.h | 6 +++++- kernel/bpf/hashtab.c | 6 +++--- kernel/bpf/verifier.c | 26 +++++++++----------------- lib/test_bpf.c | 2 +- 4 files changed, 18 insertions(+), 22 deletions(-) diff --git a/include/linux/filter.h b/include/linux/filter.h index 4a93c12543ee..6c247663d4ce 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -365,13 +365,17 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) #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) + #define BPF_EMIT_CALL(FUNC) \ ((struct bpf_insn) { \ .code = BPF_JMP | BPF_CALL, \ .dst_reg = 0, \ .src_reg = 0, \ .off = 0, \ - .imm = ((FUNC) - __bpf_call_base) }) + .imm = BPF_CALL_IMM(FUNC) }) /* Raw code statement block */ diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 32471ba02708..3d8f9d6997d5 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -668,7 +668,7 @@ static int htab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf) BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem, (void *(*)(struct bpf_map *map, void *key))NULL)); - *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem)); + *insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem); *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 1); *insn++ = BPF_ALU64_IMM(BPF_ADD, ret, offsetof(struct htab_elem, key) + @@ -709,7 +709,7 @@ static int htab_lru_map_gen_lookup(struct bpf_map *map, BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem, (void *(*)(struct bpf_map *map, void *key))NULL)); - *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem)); + *insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem); *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 4); *insn++ = BPF_LDX_MEM(BPF_B, ref_reg, ret, offsetof(struct htab_elem, lru_node) + @@ -2397,7 +2397,7 @@ static int htab_of_map_gen_lookup(struct bpf_map *map, BUILD_BUG_ON(!__same_type(&__htab_map_lookup_elem, (void *(*)(struct bpf_map *map, void *key))NULL)); - *insn++ = BPF_EMIT_CALL(BPF_CAST_CALL(__htab_map_lookup_elem)); + *insn++ = BPF_EMIT_CALL(__htab_map_lookup_elem); *insn++ = BPF_JMP_IMM(BPF_JEQ, ret, 0, 2); *insn++ = BPF_ALU64_IMM(BPF_ADD, ret, offsetof(struct htab_elem, key) + diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7a8351604f67..1433752db740 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1744,7 +1744,7 @@ static int add_kfunc_call(struct bpf_verifier_env *env, u32 func_id) desc = &tab->descs[tab->nr_descs++]; desc->func_id = func_id; - desc->imm = BPF_CAST_CALL(addr) - __bpf_call_base; + desc->imm = BPF_CALL_IMM(addr); err = btf_distill_func_proto(&env->log, btf_vmlinux, func_proto, func_name, &desc->func_model); @@ -12514,8 +12514,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) if (!bpf_pseudo_call(insn)) continue; subprog = insn->off; - insn->imm = BPF_CAST_CALL(func[subprog]->bpf_func) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(func[subprog]->bpf_func); } /* we use the aux data to keep a list of the start addresses @@ -12995,32 +12994,25 @@ static int do_misc_fixups(struct bpf_verifier_env *env) patch_map_ops_generic: switch (insn->imm) { case BPF_FUNC_map_lookup_elem: - insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_lookup_elem); continue; case BPF_FUNC_map_update_elem: - insn->imm = BPF_CAST_CALL(ops->map_update_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_update_elem); continue; case BPF_FUNC_map_delete_elem: - insn->imm = BPF_CAST_CALL(ops->map_delete_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_delete_elem); continue; case BPF_FUNC_map_push_elem: - insn->imm = BPF_CAST_CALL(ops->map_push_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_push_elem); continue; case BPF_FUNC_map_pop_elem: - insn->imm = BPF_CAST_CALL(ops->map_pop_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_pop_elem); continue; case BPF_FUNC_map_peek_elem: - insn->imm = BPF_CAST_CALL(ops->map_peek_elem) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_peek_elem); continue; case BPF_FUNC_redirect_map: - insn->imm = BPF_CAST_CALL(ops->map_redirect) - - __bpf_call_base; + insn->imm = BPF_CALL_IMM(ops->map_redirect); continue; } diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 08f438e6fe9e..21ea1ab253a1 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -12439,7 +12439,7 @@ static __init int prepare_tail_call_tests(struct bpf_array **pprogs) err = -EFAULT; goto out_err; } - *insn = BPF_EMIT_CALL(BPF_CAST_CALL(addr)); + *insn = BPF_EMIT_CALL(addr); if ((long)__bpf_call_base + insn->imm != addr) *insn = BPF_JMP_A(0); /* Skip: NOP */ break; From patchwork Tue Sep 28 23:09:46 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 12537939 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49AE4C4321E for ; Tue, 28 Sep 2021 23:10:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3A35E613B3 for ; Tue, 28 Sep 2021 23:10:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243218AbhI1XLo (ORCPT ); Tue, 28 Sep 2021 19:11:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60572 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243191AbhI1XLc (ORCPT ); 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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id n22sm212165pgc.55.2021.09.28.16.09.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Sep 2021 16:09:50 -0700 (PDT) From: Kees Cook To: Alexei Starovoitov Cc: Kees Cook , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, "Gustavo A . R . Silva" , Andrii Nakryiko , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH bpf-next v2 2/2] bpf: Replace callers of BPF_CAST_CALL with proper function typedef Date: Tue, 28 Sep 2021 16:09:46 -0700 Message-Id: <20210928230946.4062144-3-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210928230946.4062144-1-keescook@chromium.org> References: <20210928230946.4062144-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5823; h=from:subject; bh=bIODIAWxeyL04TePXGI79CL8QMIiwVlVilt68BmKwUY=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhU6C6aGYZPCX+7LX7upl8u3qYxvQjavYR/tovWoe/ 5cj6HC+JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYVOgugAKCRCJcvTf3G3AJqh4D/ 9rWQaEPtV7RuvYSZhnXiM25YXAfa8m5uB528TD0lmky4o5pugL4eg/wssw5aMplz44ciIBW8mNnMVq OO5mPJsXASrL+2xMgiLJuiKOR2vevBJ03OKYSBsu/gUSiFYW2qlX+hlrkP+ugJTUBNa10a9UfotmjM 51YZgjaZXh3ZYxqT8/Fz9oXqXkDKW15ch8724BqGdk93m9N8i4JL4FWBPM6HIXnPXH6EJOQLnntOQv tsQlQMh86KFuww0CKXjby9qqQd2ziI+lG+yzGBsMKHHrvzJVcqBi1Y99fkdCOobgFCKPxZqy7E4B1D HGafc+9hEM1SHCFMJNncxuFrbUXtM+yNIfNul4AjEeMcUPXPQkNBS0YJoxEXGV5zAkw0xKBZ8Ixk7g A994g2uerkAbA3fVNVkDupG1S3CYGdkthYv0jlrAitXS20Ri6xNefULdaPA9QWYKvawSHmzYx8vsfN xbAYoIEHK5Ko2YOzffdvnsHSpml3SWh4a90IDHzxyt57ceH95hFrXN1x2RT6Bl9NqYYSZsFsm+7UCc SVX5+4S0Zo/upEL3TCGr5m65WRXI9WlIVReb4rWTcnt7mZaArSiBhME1qf1hTeazu83653Bk4zUgfy 3u+YHQ76l1id476SERYHb8HVCEKowAxJpH/3uOmmRuAqOHUC3085wLuBC6hg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@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: 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 Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/lkml/CAEf4Bzb46=-J5Fxc3mMZ8JQPtK1uoE0q6+g6WPz53Cvx=CBEhw@mail.gmail.com Acked-by: Gustavo A. R. Silva --- 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 b6c45a6cbbba..19735d59230a 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 2c604ff8c7fb..1ffd469c217f 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -1056,7 +1056,7 @@ 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; @@ -1081,8 +1081,7 @@ 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);