user/sven/linux.git/scripts/Makefile.kasan, branch v5.4.249

kasan/arm64: fix CONFIG_KASAN_SW_TAGS && KASAN_INLINE

2019-08-15T12:24:04Z

The generic Makefile.kasan propagates CONFIG_KASAN_SHADOW_OFFSET into KASAN_SHADOW_OFFSET, but only does so for CONFIG_KASAN_GENERIC. Since commit: 6bd1d0be0e97936d ("arm64: kasan: Switch to using KASAN_SHADOW_OFFSET") ... arm64 defines CONFIG_KASAN_SHADOW_OFFSET in Kconfig rather than defining KASAN_SHADOW_OFFSET in a Makefile. Thus, if CONFIG_KASAN_SW_TAGS && KASAN_INLINE are selected, we get build time splats due to KASAN_SHADOW_OFFSET not being set: | [mark@lakrids:~/src/linux]% usellvm 8.0.1 usekorg 8.1.0 make ARCH=arm64 CROSS_COMPILE=aarch64-linux- CC=clang | scripts/kconfig/conf --syncconfig Kconfig | CC scripts/mod/empty.o | clang (LLVM option parsing): for the -hwasan-mapping-offset option: '' value invalid for uint argument! | scripts/Makefile.build:273: recipe for target 'scripts/mod/empty.o' failed | make[1]: *** [scripts/mod/empty.o] Error 1 | Makefile:1123: recipe for target 'prepare0' failed | make: *** [prepare0] Error 2 Let's fix this by always propagating CONFIG_KASAN_SHADOW_OFFSET into KASAN_SHADOW_OFFSET if CONFIG_KASAN is selected, moving the existing common definition of +CFLAGS_KASAN_NOSANITIZE to the top of Makefile.kasan. Cc: Catalin Marinas Signed-off-by: Mark Rutland Acked-by: Andrey Ryabinin Tested-by Steve Capper Signed-off-by: Will Deacon

kasan: remove use after scope bugs detection.

2019-03-06T05:07:13Z

Use after scope bugs detector seems to be almost entirely useless for the linux kernel. It exists over two years, but I've seen only one valid bug so far [1]. And the bug was fixed before it has been reported. There were some other use-after-scope reports, but they were false-positives due to different reasons like incompatibility with structleak plugin. This feature significantly increases stack usage, especially with GCC < 9 version, and causes a 32K stack overflow. It probably adds performance penalty too. Given all that, let's remove use-after-scope detector entirely. While preparing this patch I've noticed that we mistakenly enable use-after-scope detection for clang compiler regardless of CONFIG_KASAN_EXTRA setting. This is also fixed now. [1] http://lkml.kernel.org/r/<20171129052106.rhgbjhhis53hkgfn@wfg-t540p.sh.intel.com> Link: http://lkml.kernel.org/r/20190111185842.13978-1-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Acked-by: Will Deacon [arm64] Cc: Qian Cai Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Catalin Marinas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: turn off asan-stack for clang-8 and earlier

2019-03-01T17:02:33Z

Building an arm64 allmodconfig kernel with clang results in over 140 warnings about overly large stack frames, the worst ones being: drivers/gpu/drm/panel/panel-sitronix-st7789v.c:196:12: error: stack frame size of 20224 bytes in function 'st7789v_prepare' drivers/video/fbdev/omap2/omapfb/displays/panel-tpo-td028ttec1.c:196:12: error: stack frame size of 13120 bytes in function 'td028ttec1_panel_enable' drivers/usb/host/max3421-hcd.c:1395:1: error: stack frame size of 10048 bytes in function 'max3421_spi_thread' drivers/net/wan/slic_ds26522.c:209:12: error: stack frame size of 9664 bytes in function 'slic_ds26522_probe' drivers/crypto/ccp/ccp-ops.c:2434:5: error: stack frame size of 8832 bytes in function 'ccp_run_cmd' drivers/media/dvb-frontends/stv0367.c:1005:12: error: stack frame size of 7840 bytes in function 'stv0367ter_algo' None of these happen with gcc today, and almost all of these are the result of a single known issue in llvm. Hopefully it will eventually get fixed with the clang-9 release. In the meantime, the best idea I have is to turn off asan-stack for clang-8 and earlier, so we can produce a kernel that is safe to run. I have posted three patches that address the frame overflow warnings that are not addressed by turning off asan-stack, so in combination with this change, we get much closer to a clean allmodconfig build, which in turn is necessary to do meaningful build regression testing. It is still possible to turn on the CONFIG_ASAN_STACK option on all versions of clang, and it's always enabled for gcc, but when CONFIG_COMPILE_TEST is set, the option remains invisible, so allmodconfig and randconfig builds (which are normally done with a forced CONFIG_COMPILE_TEST) will still result in a mostly clean build. Link: http://lkml.kernel.org/r/20190222222950.3997333-1-arnd@arndb.de Link: https://bugs.llvm.org/show_bug.cgi?id=38809 Signed-off-by: Arnd Bergmann Reviewed-by: Qian Cai Reviewed-by: Mark Brown Acked-by: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Nick Desaulniers Cc: Kostya Serebryany Cc: Andrey Konovalov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: add CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS

2018-12-28T20:11:43Z

This commit splits the current CONFIG_KASAN config option into two: 1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one that exists now); 2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode. The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have another hardware tag-based KASAN mode, that will rely on hardware memory tagging support in arm64. With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to instrument kernel files with -fsantize=kernel-hwaddress (except the ones for which KASAN_SANITIZE := n is set). Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes. This commit also adds empty placeholder (for now) implementation of tag-based KASAN specific hooks inserted by the compiler and adjusts common hooks implementation. While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will enable once all the infrastracture code has been added. Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Andrey Ryabinin Reviewed-by: Dmitry Vyukov Cc: Christoph Lameter Cc: Mark Rutland Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: rework Kconfig settings

2018-02-07T02:32:47Z

We get a lot of very large stack frames using gcc-7.0.1 with the default -fsanitize-address-use-after-scope --param asan-stack=1 options, which can easily cause an overflow of the kernel stack, e.g. drivers/gpu/drm/i915/gvt/handlers.c:2434:1: warning: the frame size of 46176 bytes is larger than 3072 bytes drivers/net/wireless/ralink/rt2x00/rt2800lib.c:5650:1: warning: the frame size of 23632 bytes is larger than 3072 bytes lib/atomic64_test.c:250:1: warning: the frame size of 11200 bytes is larger than 3072 bytes drivers/gpu/drm/i915/gvt/handlers.c:2621:1: warning: the frame size of 9208 bytes is larger than 3072 bytes drivers/media/dvb-frontends/stv090x.c:3431:1: warning: the frame size of 6816 bytes is larger than 3072 bytes fs/fscache/stats.c:287:1: warning: the frame size of 6536 bytes is larger than 3072 bytes To reduce this risk, -fsanitize-address-use-after-scope is now split out into a separate CONFIG_KASAN_EXTRA Kconfig option, leading to stack frames that are smaller than 2 kilobytes most of the time on x86_64. An earlier version of this patch also prevented combining KASAN_EXTRA with KASAN_INLINE, but that is no longer necessary with gcc-7.0.1. All patches to get the frame size below 2048 bytes with CONFIG_KASAN=y and CONFIG_KASAN_EXTRA=n have been merged by maintainers now, so we can bring back that default now. KASAN_EXTRA=y still causes lots of warnings but now defaults to !COMPILE_TEST to disable it in allmodconfig, and it remains disabled in all other defconfigs since it is a new option. I arbitrarily raise the warning limit for KASAN_EXTRA to 3072 to reduce the noise, but an allmodconfig kernel still has around 50 warnings on gcc-7. I experimented a bit more with smaller stack frames and have another follow-up series that reduces the warning limit for 64-bit architectures to 1280 bytes (without CONFIG_KASAN). With earlier versions of this patch series, I also had patches to address the warnings we get with KASAN and/or KASAN_EXTRA, using a "noinline_if_stackbloat" annotation. That annotation now got replaced with a gcc-8 bugfix (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715) and a workaround for older compilers, which means that KASAN_EXTRA is now just as bad as before and will lead to an instant stack overflow in a few extreme cases. This reverts parts of commit 3f181b4d8652 ("lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y"). Two patches in linux-next should be merged first to avoid introducing warnings in an allmodconfig build: 3cd890dbe2a4 ("media: dvb-frontends: fix i2c access helpers for KASAN") 16c3ada89cff ("media: r820t: fix r820t_write_reg for KASAN") Do we really need to backport this? I think we do: without this patch, enabling KASAN will lead to unavoidable kernel stack overflow in certain device drivers when built with gcc-7 or higher on linux-4.10+ or any version that contains a backport of commit c5caf21ab0cf8. Most people are probably still on older compilers, but it will get worse over time as they upgrade their distros. The warnings we get on kernels older than this should all be for code that uses dangerously large stack frames, though most of them do not cause an actual stack overflow by themselves.The asan-stack option was added in linux-4.0, and commit 3f181b4d8652 ("lib/Kconfig.debug: disable -Wframe-larger-than warnings with KASAN=y") effectively turned off the warning for allmodconfig kernels, so I would like to see this fix backported to any kernels later than 4.0. I have done dozens of fixes for individual functions with stack frames larger than 2048 bytes with asan-stack, and I plan to make sure that all those fixes make it into the stable kernels as well (most are already there). Part of the complication here is that asan-stack (from 4.0) was originally assumed to always require much larger stacks, but that turned out to be a combination of multiple gcc bugs that we have now worked around and fixed, but sanitize-address-use-after-scope (from v4.10) has a much higher inherent stack usage and also suffers from at least three other problems that we have analyzed but not yet fixed upstream, each of them makes the stack usage more severe than it should be. Link: http://lkml.kernel.org/r/20171221134744.2295529-1-arnd@arndb.de Signed-off-by: Arnd Bergmann Acked-by: Andrey Ryabinin Cc: Mauro Carvalho Chehab Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Andrey Konovalov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: support alloca() poisoning

2018-02-07T02:32:42Z

clang's AddressSanitizer implementation adds redzones on either side of alloca()ed buffers. These redzones are 32-byte aligned and at least 32 bytes long. __asan_alloca_poison() is passed the size and address of the allocated buffer, *excluding* the redzones on either side. The left redzone will always be to the immediate left of this buffer; but AddressSanitizer may need to add padding between the end of the buffer and the right redzone. If there are any 8-byte chunks inside this padding, we should poison those too. __asan_allocas_unpoison() is just passed the top and bottom of the dynamic stack area, so unpoisoning is simpler. Link: http://lkml.kernel.org/r/20171204191735.132544-4-paullawrence@google.com Signed-off-by: Greg Hackmann Signed-off-by: Paul Lawrence Acked-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Masahiro Yamada Cc: Matthias Kaehlcke Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan/Makefile: support LLVM style asan parameters

2018-02-07T02:32:42Z

LLVM doesn't understand GCC-style paramters ("--param asan-foo=bar"), thus we currently we don't use inline/globals/stack instrumentation when building the kernel with clang. Add support for LLVM-style parameters ("-mllvm -asan-foo=bar") to enable all KASAN features. Link: http://lkml.kernel.org/r/20171204191735.132544-3-paullawrence@google.com Signed-off-by: Andrey Ryabinin Signed-off-by: Paul Lawrence Reviewed-by: Alexander Potapenko Cc: Dmitry Vyukov Cc: Greg Hackmann Cc: Masahiro Yamada Cc: Matthias Kaehlcke Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: don't emit builtin calls when sanitization is off

2018-02-07T02:32:42Z

With KASAN enabled the kernel has two different memset() functions, one with KASAN checks (memset) and one without (__memset). KASAN uses some macro tricks to use the proper version where required. For example memset() calls in mm/slub.c are without KASAN checks, since they operate on poisoned slab object metadata. The issue is that clang emits memset() calls even when there is no memset() in the source code. They get linked with improper memset() implementation and the kernel fails to boot due to a huge amount of KASAN reports during early boot stages. The solution is to add -fno-builtin flag for files with KASAN_SANITIZE := n marker. Link: http://lkml.kernel.org/r/8ffecfffe04088c52c42b92739c2bd8a0bcb3f5e.1516384594.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Acked-by: Nick Desaulniers Cc: Masahiro Yamada Cc: Michal Marek Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55Z

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

kasan: turn on -fsanitize-address-use-after-scope

2016-12-13T02:55:09Z

In the upcoming gcc7 release, the -fsanitize=kernel-address option at first implied new -fsanitize-address-use-after-scope option. This would cause link errors on older kernels because they don't have two new functions required for use-after-scope support. Therefore, gcc7 changed default to -fno-sanitize-address-use-after-scope. Now the kernel has everything required for that feature since commit 828347f8f9a5 ("kasan: support use-after-scope detection"). So, to make it work, we just have to enable use-after-scope in CFLAGS. Link: http://lkml.kernel.org/r/1481207977-28654-1-git-send-email-aryabinin@virtuozzo.com Signed-off-by: Andrey Ryabinin Acked-by: Dmitry Vyukov Cc: Alexander Potapenko Cc: Andrey Konovalov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds