From: Kees Cook <keescook@chromium.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: linux-hardening@vger.kernel.org,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Keith Packard <keithpac@amazon.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
netdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-staging@lists.linux.dev, linux-block@vger.kernel.org,
linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH 34/64] fortify: Detect struct member overflows in memcpy() at compile-time
Date: Tue, 27 Jul 2021 18:47:52 -0700 [thread overview]
Message-ID: <202107271830.3DB03F3CF@keescook> (raw)
In-Reply-To: <CAKwvOdknit8DtWaFvLupmNEebjbwVa6R3xiGc2D4AqB_6+i52g@mail.gmail.com>
On Tue, Jul 27, 2021 at 03:43:27PM -0700, Nick Desaulniers wrote:
> On Tue, Jul 27, 2021 at 2:17 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > To accelerate the review of potential run-time false positives, it's
> > also worth noting that it is possible to partially automate checking
> > by examining memcpy() buffer argument fields to see if they have
> > a neighboring. It is reasonable to expect that the vast majority of
>
> a neighboring...field?
Whoops, sorry, this should say "array member". I've fixed this to read:
To accelerate the review of potential run-time false positives, it's
also worth noting that it is possible to partially automate checking
by examining the memcpy() buffer argument to check for the destination
struct member having a neighboring array member. It is reasonable to
expect that the vast majority of run-time false positives would look like
the already evaluated and fixed compile-time false positives, where the
most common pattern is neighboring arrays. (And, FWIW, several of the
compile-time fixes were actual bugs.)
> > diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
> > index 7e67d02764db..5e79e626172b 100644
> > --- a/include/linux/fortify-string.h
> > +++ b/include/linux/fortify-string.h
> > @@ -2,13 +2,17 @@
> > #ifndef _LINUX_FORTIFY_STRING_H_
> > #define _LINUX_FORTIFY_STRING_H_
> >
> > +#include <linux/bug.h>
>
> What are you using from linux/bug.h here?
Thanks; yes, that should have been added in patch 64, when the WARN_ONCE()
use is introduced:
https://lore.kernel.org/lkml/20210727205855.411487-65-keescook@chromium.org/
> > [...]
> > +#define __fortify_memcpy_chk(p, q, size, p_size, q_size, \
> > + p_size_field, q_size_field, op) ({ \
> > + size_t __fortify_size = (size_t)(size); \
> > + fortify_memcpy_chk(__fortify_size, p_size, q_size, \
> > + p_size_field, q_size_field, #op); \
> > + __underlying_##op(p, q, __fortify_size); \
> > +})
> > +
> > +/*
> > + * __builtin_object_size() must be captured here to avoid evaluating argument
> > + * side-effects further into the macro layers.
> > + */
> > +#define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \
> > + __builtin_object_size(p, 0), __builtin_object_size(q, 0), \
> > + __builtin_object_size(p, 1), __builtin_object_size(q, 1), \
> > + memcpy)
>
> Are there other macro expansion sites for `__fortify_memcpy_chk`,
> perhaps later in this series? I don't understand why `memcpy` is
> passed as `func` to `fortify_panic()` rather than continuing to use
> `__func__`?
Yes, memmove() follows exactly the same pattern. Rather than refactoring
the declaration in that patch, this felt cleaner.
https://lore.kernel.org/lkml/20210727205855.411487-36-keescook@chromium.org/
> > [...]
> > * @count: The number of bytes to copy
> > * @pad: Character to use for padding if space is left in destination.
> > */
> > -static inline void memcpy_and_pad(void *dest, size_t dest_len,
> > - const void *src, size_t count, int pad)
> > +static __always_inline void memcpy_and_pad(void *dest, size_t dest_len,
> > + const void *src, size_t count,
> > + int pad)
>
> Why __always_inline here?
Without it, we run the risk of it being made out of line, and
potentially losing access to the __builtin_object_size() checking of
arguments. Though given some of the Clang bugs, it's possible this needs
to be strictly converted into a macro.
> > [...]
> > #ifdef CONFIG_FORTIFY_SOURCE
> > +/* These are placeholders for fortify compile-time warnings. */
> > +void __read_overflow2_field(void) { }
> > +EXPORT_SYMBOL(__read_overflow2_field);
> > +void __write_overflow_field(void) { }
> > +EXPORT_SYMBOL(__write_overflow_field);
> > +
>
> Don't we rely on these being undefined for Clang to produce a linkage
> failure (until https://reviews.llvm.org/D106030 has landed)? By
> providing a symbol definition we can link against, I don't think
> __compiletime_{warning|error} will warn at all with Clang?
This was intentional because I explicitly do not want to break the build
for new warnings, and there is no way currently for Clang to _warn_
(rather than fail to link). This could be adjusted to break only Clang's
builds, but at this point, it seemed best.
> > [...]
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +#define TEST \
> > + memcpy(instance.buf, large, sizeof(instance.buf) + 1)
> > +
> > +#include "test_fortify.h"
> > --
>
> I haven't read the whole series yet, but I assume test_fortify.h was
> provided earlier in the series?
Yup, it's part of the compile-time tests in patch 32:
https://lore.kernel.org/lkml/20210727205855.411487-33-keescook@chromium.org/
-Kees
--
Kees Cook
next prev parent reply other threads:[~2021-07-28 1:47 UTC|newest]
Thread overview: 158+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-27 20:57 [PATCH 00/64] Introduce strict memcpy() bounds checking Kees Cook
2021-07-27 20:57 ` [PATCH 01/64] media: omap3isp: Extract struct group for memcpy() region Kees Cook
2021-07-28 0:55 ` Gustavo A. R. Silva
2021-07-28 1:50 ` Kees Cook
2021-07-28 8:59 ` David Sterba
2021-07-28 9:14 ` Dan Carpenter
2021-07-28 21:37 ` Bart Van Assche
2021-07-28 21:37 ` David Sterba
2021-07-29 5:56 ` Greg Kroah-Hartman
2021-07-29 8:20 ` Dan Carpenter
2021-07-30 6:00 ` Kees Cook
2021-07-30 8:38 ` David Sterba
2021-07-30 9:00 ` Dan Carpenter
2021-07-30 16:44 ` Kees Cook
2021-07-30 17:08 ` Nick Desaulniers
2021-07-30 19:18 ` Kees Cook
2021-07-27 20:57 ` [PATCH 02/64] mac80211: Use flex-array for radiotap header bitmap Kees Cook
2021-07-28 7:35 ` Dan Carpenter
2021-07-28 9:23 ` David Sterba
2021-07-28 21:54 ` Kees Cook
2021-07-29 10:45 ` David Sterba
2021-07-30 6:06 ` Kees Cook
2021-07-28 21:20 ` Kees Cook
2021-07-28 23:14 ` Kees Cook
2021-07-28 23:33 ` Kees Cook
2021-07-29 8:25 ` Dan Carpenter
2021-07-27 20:57 ` [PATCH 03/64] rpmsg: glink: Replace strncpy() with strscpy_pad() Kees Cook
2021-07-28 2:07 ` Gustavo A. R. Silva
2021-07-27 20:57 ` [PATCH 04/64] stddef: Introduce struct_group() helper macro Kees Cook
2021-07-28 2:32 ` Gustavo A. R. Silva
2021-07-28 10:54 ` Rasmus Villemoes
2021-07-28 21:59 ` Kees Cook
2021-07-30 22:19 ` Williams, Dan J
2021-07-31 2:59 ` Kees Cook
[not found] ` <CAKwiHFheDv2pwsm6Fa+-KnOFyvk7bfZQjb2BQ-CSwH61gxgVYg@mail.gmail.com>
2021-07-31 15:10 ` Kees Cook
2021-07-27 20:57 ` [PATCH 05/64] skbuff: Switch structure bounds to struct_group() Kees Cook
2021-07-28 3:50 ` Gustavo A. R. Silva
2021-07-27 20:57 ` [PATCH 06/64] bnxt_en: Use struct_group_attr() for memcpy() region Kees Cook
2021-07-28 1:03 ` Michael Chan
2021-07-28 4:45 ` Gustavo A. R. Silva
2021-07-27 20:57 ` [PATCH 07/64] staging: rtl8192e: Use struct_group() " Kees Cook
2021-07-27 22:30 ` Larry Finger
2021-07-28 5:45 ` Greg Kroah-Hartman
2021-07-27 20:57 ` [PATCH 08/64] staging: rtl8192u: " Kees Cook
2021-07-28 5:45 ` Greg Kroah-Hartman
2021-07-27 20:58 ` [PATCH 09/64] staging: rtl8723bs: Avoid field-overflowing memcpy() Kees Cook
2021-07-28 5:46 ` Greg Kroah-Hartman
2021-07-27 20:58 ` [PATCH 10/64] lib80211: Use struct_group() for memcpy() region Kees Cook
2021-07-28 5:52 ` Greg Kroah-Hartman
2021-08-13 8:04 ` Johannes Berg
2021-08-13 15:49 ` Kees Cook
2021-08-13 19:44 ` Johannes Berg
2021-07-27 20:58 ` [PATCH 11/64] net/mlx5e: Avoid field-overflowing memcpy() Kees Cook
2021-07-27 20:58 ` [PATCH 12/64] mwl8k: Use struct_group() for memcpy() region Kees Cook
2021-07-27 20:58 ` [PATCH 13/64] libertas: " Kees Cook
2021-07-27 20:58 ` [PATCH 14/64] libertas_tf: " Kees Cook
2021-07-27 20:58 ` [PATCH 15/64] ipw2x00: " Kees Cook
2021-07-28 18:55 ` Stanislav Yakovlev
2021-07-27 20:58 ` [PATCH 16/64] thermal: intel: int340x_thermal: " Kees Cook
2021-07-27 20:58 ` [PATCH 17/64] iommu/amd: " Kees Cook
2021-07-27 20:58 ` [PATCH 18/64] cxgb3: " Kees Cook
2021-07-27 20:58 ` [PATCH 19/64] ip: Use struct_group() for memcpy() regions Kees Cook
2021-07-28 5:55 ` Greg Kroah-Hartman
2021-07-28 6:14 ` Gustavo A. R. Silva
2021-07-28 6:19 ` Greg Kroah-Hartman
2021-07-28 6:31 ` Gustavo A. R. Silva
2021-07-28 6:37 ` Gustavo A. R. Silva
2021-07-28 6:41 ` Greg Kroah-Hartman
2021-07-28 21:01 ` Kees Cook
2021-07-29 1:59 ` Bart Van Assche
2021-07-27 20:58 ` [PATCH 20/64] intersil: Use struct_group() for memcpy() region Kees Cook
2021-07-27 20:58 ` [PATCH 21/64] cxgb4: " Kees Cook
2021-07-27 20:58 ` [PATCH 22/64] bnx2x: " Kees Cook
2021-07-27 20:58 ` [PATCH 23/64] drm/amd/pm: " Kees Cook
2021-07-30 2:07 ` Alex Deucher
2021-07-27 20:58 ` [PATCH 24/64] staging: wlan-ng: " Kees Cook
2021-07-28 5:45 ` Greg Kroah-Hartman
2021-07-27 20:58 ` [PATCH 25/64] drm/mga/mga_ioc32: " Kees Cook
2021-07-28 5:56 ` Greg Kroah-Hartman
2021-07-29 12:11 ` Daniel Vetter
2021-07-31 4:20 ` Kees Cook
2021-07-27 20:58 ` [PATCH 26/64] net/mlx5e: " Kees Cook
2021-07-27 20:58 ` [PATCH 27/64] HID: cp2112: " Kees Cook
2021-07-27 20:58 ` [PATCH 28/64] compiler_types.h: Remove __compiletime_object_size() Kees Cook
2021-07-27 20:58 ` [PATCH 29/64] lib/string: Move helper functions out of string.c Kees Cook
2021-07-27 20:58 ` [PATCH 30/64] fortify: Move remaining fortify helpers into fortify-string.h Kees Cook
2021-07-27 20:58 ` [PATCH 31/64] fortify: Explicitly disable Clang support Kees Cook
2021-07-27 21:18 ` Nathan Chancellor
2021-07-27 21:47 ` Kees Cook
2021-07-27 20:58 ` [PATCH 32/64] fortify: Add compile-time FORTIFY_SOURCE tests Kees Cook
2021-07-27 20:58 ` [PATCH 33/64] lib: Introduce CONFIG_TEST_MEMCPY Kees Cook
2021-07-27 23:31 ` Bart Van Assche
2021-07-27 23:33 ` Randy Dunlap
2021-07-28 1:30 ` Kees Cook
2021-07-27 20:58 ` [PATCH 34/64] fortify: Detect struct member overflows in memcpy() at compile-time Kees Cook
2021-07-27 22:43 ` Nick Desaulniers
2021-07-28 1:47 ` Kees Cook [this message]
2021-07-28 11:19 ` Rasmus Villemoes
2021-07-30 2:39 ` Kees Cook
2021-07-27 20:58 ` [PATCH 35/64] fortify: Detect struct member overflows in memmove() " Kees Cook
2021-07-27 20:58 ` [PATCH 36/64] scsi: ibmvscsi: Avoid multi-field memset() overflow by aiming at srp Kees Cook
2021-07-28 1:39 ` Martin K. Petersen
2021-07-28 18:57 ` Kees Cook
2021-07-29 3:35 ` Martin K. Petersen
2021-07-30 19:11 ` Tyrel Datwyler
2021-07-30 18:16 ` Tyrel Datwyler
2021-07-27 20:58 ` [PATCH 37/64] string.h: Introduce memset_after() for wiping trailing members/padding Kees Cook
2021-07-27 20:58 ` [PATCH 38/64] xfrm: Use memset_after() to clear padding Kees Cook
2021-07-27 20:58 ` [PATCH 39/64] mac80211: Use memset_after() to clear tx status Kees Cook
2021-07-31 15:55 ` Kees Cook
2021-08-13 7:40 ` Johannes Berg
2021-08-13 16:08 ` Kees Cook
2021-08-13 18:19 ` Johannes Berg
2021-08-13 7:41 ` Johannes Berg
2021-07-27 20:58 ` [PATCH 40/64] net: 802: Use memset_after() to clear struct fields Kees Cook
2021-07-27 20:58 ` [PATCH 41/64] net: dccp: Use memset_after() for TP zeroing Kees Cook
2021-07-27 20:58 ` [PATCH 42/64] net: qede: Use memset_after() for counters Kees Cook
2021-07-31 16:07 ` Kees Cook
2021-07-27 20:58 ` [PATCH 43/64] ath11k: Use memset_after() for clearing queue descriptors Kees Cook
2021-07-27 20:58 ` [PATCH 44/64] iw_cxgb4: Use memset_after() for cpl_t5_pass_accept_rpl Kees Cook
2021-07-27 20:58 ` [PATCH 45/64] intel_th: msu: Use memset_after() for clearing hw header Kees Cook
2021-07-27 20:58 ` [PATCH 46/64] IB/mthca: Use memset_after() for clearing mpt_entry Kees Cook
2021-07-27 20:58 ` [PATCH 47/64] btrfs: Use memset_after() to clear end of struct Kees Cook
2021-07-28 9:42 ` David Sterba
2021-07-28 21:56 ` Kees Cook
2021-07-29 10:33 ` David Sterba
2021-07-31 15:25 ` Kees Cook
2021-08-09 11:20 ` David Sterba
2021-07-27 20:58 ` [PATCH 48/64] drbd: Use struct_group() to zero algs Kees Cook
2021-07-28 21:45 ` Bart Van Assche
2021-07-30 2:31 ` Kees Cook
2021-07-30 2:57 ` Bart Van Assche
2021-07-30 9:25 ` Lars Ellenberg
2021-07-30 15:32 ` Nick Desaulniers
2021-07-27 20:58 ` [PATCH 49/64] cm4000_cs: Use struct_group() to zero struct cm4000_dev region Kees Cook
2021-07-28 5:48 ` Greg Kroah-Hartman
2021-07-27 20:58 ` [PATCH 50/64] KVM: x86: Use struct_group() to zero decode cache Kees Cook
2021-07-27 20:58 ` [PATCH 51/64] tracing: Use struct_group() to zero struct trace_iterator Kees Cook
2021-07-27 20:58 ` [PATCH 52/64] dm integrity: Use struct_group() to zero struct journal_sector Kees Cook
2021-07-27 20:58 ` [PATCH 53/64] HID: roccat: Use struct_group() to zero kone_mouse_event Kees Cook
2021-07-27 20:58 ` [PATCH 54/64] ipv6: Use struct_group() to zero rt6_info Kees Cook
2021-07-29 18:58 ` Jakub Kicinski
2021-07-31 15:01 ` Kees Cook
2021-07-27 20:58 ` [PATCH 55/64] RDMA/mlx5: Use struct_group() to zero struct mlx5_ib_mr Kees Cook
2021-07-27 20:58 ` [PATCH 56/64] ethtool: stats: Use struct_group() to clear all stats at once Kees Cook
2021-07-27 20:58 ` [PATCH 57/64] netfilter: conntrack: Use struct_group() to zero struct nf_conn Kees Cook
2021-07-27 20:58 ` [PATCH 58/64] powerpc: Split memset() to avoid multi-field overflow Kees Cook
2021-08-05 11:36 ` Michael Ellerman
2021-07-27 20:58 ` [PATCH 59/64] fortify: Detect struct member overflows in memset() at compile-time Kees Cook
2021-07-27 20:58 ` [PATCH 60/64] fortify: Work around Clang inlining bugs Kees Cook
2021-07-27 20:58 ` [PATCH 61/64] Makefile: Enable -Warray-bounds Kees Cook
2021-07-27 20:58 ` [PATCH 62/64] netlink: Avoid false-positive memcpy() warning Kees Cook
2021-07-28 5:49 ` Greg Kroah-Hartman
2021-07-28 11:24 ` Rasmus Villemoes
2021-07-30 1:39 ` Kees Cook
2021-07-30 1:41 ` Kees Cook
2021-07-27 20:58 ` [PATCH 63/64] iwlwifi: dbg_ini: Split memcpy() to avoid multi-field write Kees Cook
2021-07-27 20:58 ` [PATCH 64/64] fortify: Add run-time WARN for cross-field memcpy() Kees Cook
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