From mboxrd@z Thu Jan 1 00:00:00 1970 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C743AC433FE for ; Tue, 18 Oct 2022 18:07:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230027AbiJRSHp (ORCPT ); Tue, 18 Oct 2022 14:07:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37684 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229680AbiJRSHl (ORCPT ); Tue, 18 Oct 2022 14:07:41 -0400 Received: from mail-pg1-x54a.google.com (mail-pg1-x54a.google.com [IPv6:2607:f8b0:4864:20::54a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9EB7E5C363 for ; Tue, 18 Oct 2022 11:07:40 -0700 (PDT) Received: by mail-pg1-x54a.google.com with SMTP id j12-20020a63594c000000b004468ff8fc78so8458632pgm.10 for ; Tue, 18 Oct 2022 11:07:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=fuVjSplyBXIPd7uWO393ugBi/njAUtKrGdSOK72nMMo=; b=oCN1jDfBFe0TZVpGUlaA/ZZtrXqmMoDyg2Xic0OjjoRanJrpKg517yTqDVe7dRqy1z AECFSeXfdl6b3KJLmBTghr1pR/Nr9a8QYIF5TCOoHrJK6RyQOIJP4v7VtxdfhiMZGiMe azHmeZmV5QC73wA/YZ5PxwDh1ZrG07R8yXJ5aBcHUDYiFEFs8G0EEhOn4mHrf9S2Qa8D D9CjqmSfzRR87v/AwVqgXtnheJOW8h3zbqyn6O05QmNYCFyuwkJFD0kdqFt6UzlcZhV8 kGT1vGW4q+ZuieONJelSFhWDo9sjwExgKB0x75CtI6xQsti11GJN+yl9VLGsueaCA/zM IsRg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=fuVjSplyBXIPd7uWO393ugBi/njAUtKrGdSOK72nMMo=; b=ojGLanj43YVw5YramfT99rhQ7nt7ISDGFFg0RwjW23idOO8+fpio8zkJMou+Q9GaWd Fr46N7qXZccwdL47hjFjQpD4E2q47TGApHecN0OMeZ03NHwzRv/tjFRbV9fcy4+APtMN UYj5sVa7anFv8gdbjlQqJNA8LVM8iv6ZlQiADYFhX1b5bKMBZGGX1qWEtK2+lEYdknOq ecS47bIJHimJkFEi+/Vmqt/pO5J3z9x+jpGUJuUGwurEiTxjr8BUv/MZgdR6fxByVbFs 5o2bp2KqZIe2qXP4dJ8m8p5D0XDZUlPteoYsFyPna0ivuyHpRLrFmxYW1cmg/s78OnpH HQ7Q== X-Gm-Message-State: ACrzQf1aIoxfiD+41iSB0/Cy142wzLaaGcZqzGqmO+NKgbF9YivgYlIJ lur/LyDBk7eiHOrkTOm/y1vnMOE= X-Google-Smtp-Source: AMsMyM4kTW3fLnTML3Zt8GdvqSub4ZsxSFSiIsHj8w9JHnGzIiT4SuAdzosdCmimydC5OKOcFwwsCZs= X-Received: from sdf.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5935]) (user=sdf job=sendgmr) by 2002:a05:6a00:1707:b0:562:e790:dfc3 with SMTP id h7-20020a056a00170700b00562e790dfc3mr4484929pfc.59.1666116460090; Tue, 18 Oct 2022 11:07:40 -0700 (PDT) Date: Tue, 18 Oct 2022 11:07:38 -0700 In-Reply-To: <20221018090550.never.834-kees@kernel.org> Mime-Version: 1.0 References: <20221018090550.never.834-kees@kernel.org> Message-ID: Subject: Re: [PATCH] bpf: Use kmalloc_size_roundup() to match ksize() usage From: sdf@google.com To: Kees Cook Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/18, Kees Cook wrote: > Round up allocations with kmalloc_size_roundup() so that the verifier's > use of ksize() is always accurate and no special handling of the memory > is needed by KASAN, UBSAN_BOUNDS, nor FORTIFY_SOURCE. Pass the new size > information back up to callers so they can use the space immediately, > so array resizing to happen less frequently as well. Explicitly zero > any trailing bytes in new allocations. > Additionally fix a memory allocation leak: if krealloc() fails, "arr" > wasn't freed, but NULL was return to the caller of realloc_array() would > be writing NULL to the lvalue, losing the reference to the original > memory. > Cc: Alexei Starovoitov > Cc: Daniel Borkmann > Cc: John Fastabend > Cc: Andrii Nakryiko > Cc: Martin KaFai Lau > Cc: Song Liu > Cc: Yonghong Song > Cc: KP Singh > Cc: Stanislav Fomichev > Cc: Hao Luo > Cc: Jiri Olsa > Cc: bpf@vger.kernel.org > Signed-off-by: Kees Cook > --- > kernel/bpf/verifier.c | 49 +++++++++++++++++++++++++++---------------- > 1 file changed, 31 insertions(+), 18 deletions(-) > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index 014ee0953dbd..8a0b60207d0e 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -1000,42 +1000,53 @@ static void print_insn_state(struct > bpf_verifier_env *env, > */ > static void *copy_array(void *dst, const void *src, size_t n, size_t > size, gfp_t flags) > { > - size_t bytes; > + size_t src_bytes, dst_bytes; > if (ZERO_OR_NULL_PTR(src)) > goto out; > - if (unlikely(check_mul_overflow(n, size, &bytes))) > + if (unlikely(check_mul_overflow(n, size, &src_bytes))) > return NULL; > - if (ksize(dst) < bytes) { > + dst_bytes = kmalloc_size_roundup(src_bytes); > + if (ksize(dst) < dst_bytes) { Why not simply do the following here? if (ksize(dst) < ksize(src)) { ? It seems like we care about src_bytes/bytes only in this case, so maybe move that check_mul_overflow under this branch as well? > kfree(dst); > - dst = kmalloc_track_caller(bytes, flags); > + dst = kmalloc_track_caller(dst_bytes, flags); > if (!dst) > return NULL; > } > - memcpy(dst, src, bytes); > + memcpy(dst, src, src_bytes); > + memset(dst + src_bytes, 0, dst_bytes - src_bytes); > out: > return dst ? dst : ZERO_SIZE_PTR; > } > -/* resize an array from old_n items to new_n items. the array is > reallocated if it's too > - * small to hold new_n items. new items are zeroed out if the array > grows. > +/* Resize an array from old_n items to *new_n items. The array is > reallocated if it's too > + * small to hold *new_n items. New items are zeroed out if the array > grows. Allocation > + * is rounded up to next kmalloc bucket size to reduce frequency of > resizing. *new_n > + * contains the new total number of items that will fit. > * > - * Contrary to krealloc_array, does not free arr if new_n is zero. > + * Contrary to krealloc, does not free arr if new_n is zero. > */ > -static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t > size) > +static void *realloc_array(void *arr, size_t old_n, size_t *new_n, > size_t size) > { > - if (!new_n || old_n == new_n) > + void *old_arr = arr; > + size_t alloc_size; > + > + if (!new_n || !*new_n || old_n == *new_n) > goto out; [..] > - arr = krealloc_array(arr, new_n, size, GFP_KERNEL); > - if (!arr) > + alloc_size = kmalloc_size_roundup(size_mul(*new_n, size)); > + arr = krealloc(old_arr, alloc_size, GFP_KERNEL); > + if (!arr) { > + kfree(old_arr); > return NULL; > + } Any reason not do hide this complexity behind krealloc_array? Why can't it take care of those roundup details? > - if (new_n > old_n) > - memset(arr + old_n * size, 0, (new_n - old_n) * size); > + *new_n = alloc_size / size; > + if (*new_n > old_n) > + memset(arr + old_n * size, 0, (*new_n - old_n) * size); > out: > return arr ? arr : ZERO_SIZE_PTR; > @@ -1067,7 +1078,7 @@ static int copy_stack_state(struct bpf_func_state > *dst, const struct bpf_func_st > static int resize_reference_state(struct bpf_func_state *state, size_t n) > { > - state->refs = realloc_array(state->refs, state->acquired_refs, n, > + state->refs = realloc_array(state->refs, state->acquired_refs, &n, > sizeof(struct bpf_reference_state)); > if (!state->refs) > return -ENOMEM; > @@ -1083,11 +1094,11 @@ static int grow_stack_state(struct bpf_func_state > *state, int size) > if (old_n >= n) > return 0; > - state->stack = realloc_array(state->stack, old_n, n, sizeof(struct > bpf_stack_state)); > + state->stack = realloc_array(state->stack, old_n, &n, sizeof(struct > bpf_stack_state)); > if (!state->stack) > return -ENOMEM; > - state->allocated_stack = size; > + state->allocated_stack = n * BPF_REG_SIZE; > return 0; > } > @@ -2499,9 +2510,11 @@ static int push_jmp_history(struct > bpf_verifier_env *env, > { > u32 cnt = cur->jmp_history_cnt; > struct bpf_idx_pair *p; > + size_t size; > cnt++; > - p = krealloc(cur->jmp_history, cnt * sizeof(*p), GFP_USER); > + size = kmalloc_size_roundup(size_mul(cnt, sizeof(*p))); > + p = krealloc(cur->jmp_history, size, GFP_USER); > if (!p) > return -ENOMEM; > p[cnt - 1].idx = env->insn_idx; > -- > 2.34.1