- 28 Dec, 2018 40 commits
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Kuninori Morimoto authored
Update license to use SPDX-License-Identifier instead of verbose license text. Link: http://lkml.kernel.org/r/87d0qgcsz8.wl-kuninori.morimoto.gx@renesas.comSigned-off-by:
Kuninori Morimoto <kuninori.morimoto.gx@renesas.com> Reviewed-by:
Simon Horman <horms+renesas@verge.net.au> Cc: Rich Felker <dalias@libc.org> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Kuninori Morimoto authored
Update license to use SPDX-License-Identifier instead of verbose license text. Link: http://lkml.kernel.org/r/87efawcszk.wl-kuninori.morimoto.gx@renesas.comSigned-off-by:
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Kuninori Morimoto authored
Update license to use SPDX-License-Identifier instead of verbose license text. Link: http://lkml.kernel.org/r/87ftvccszx.wl-kuninori.morimoto.gx@renesas.comSigned-off-by:
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Kuninori Morimoto authored
Update license to use SPDX-License-Identifier instead of verbose license text. As original license mentioned, it is GPL-2.0 in SPDX. Then, MODULE_LICENSE() should be "GPL v2" instead of "GPL". See ${LINUX}/include/linux/module.h "GPL" [GNU Public License v2 or later] "GPL v2" [GNU Public License v2] Link: http://lkml.kernel.org/r/87h8fsct0a.wl-kuninori.morimoto.gx@renesas.comSigned-off-by: -
Kuninori Morimoto authored
Update license to use SPDX-License-Identifier instead of verbose license text. Link: http://lkml.kernel.org/r/87in08ct0n.wl-kuninori.morimoto.gx@renesas.comSigned-off-by:
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YueHaibing authored
There is no need to have the 'struct clk *camera_clk' variable static since a new value is always assigned before use. Link: http://lkml.kernel.org/r/1543628631-99957-1-git-send-email-yuehaibing@huawei.comSigned-off-by:
YueHaibing <yuehaibing@huawei.com> Reviewed-by:
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Randy Dunlap authored
arch/sh/boards/mach-kfr2r09/setup.c does not need to #include <mtd/onenand.h>, and doing so causes a build warning, so drop that header file. In file included from ../arch/sh/boards/mach-kfr2r09/setup.c:28: ../include/linux/mtd/onenand.h:225:12: warning: 'struct mtd_oob_ops' declared inside parameter list will not be visible outside of this definition or declaration struct mtd_oob_ops *ops); Link: http://lkml.kernel.org/r/702f0a25-c63e-6912-4640-6ab0f00afbc7@infradead.org Fixes: f3590dc3 ("media: arch: sh: kfr2r09: Use new renesas-ceu camera driver") Signed-off-by:Randy Dunlap <rdunlap@infradead.org> Reported-by:
Geert Uytterhoeven <geert@linux-m68k.org> Suggested-by:
Miquel Raynal <miquel.raynal@bootlin.com> Reviewed-by:
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Kirill Tkhai authored
New declarations and identifier (__always_inline). Link: http://lkml.kernel.org/r/154505048571.504.18330420599768007443.stgit@localhost.localdomainSigned-off-by:
Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Constantine Shulyupin <const@MakeLinux.com> Cc: Kirill Tkhai <ktkhai@virtuozzo.com> Cc: Joey Pabalinas <joeypabalinas@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Arend van Spriel <arend.vanspriel@broadcom.com> Signed-off-by:
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Thierry Reding authored
Add a script that will run spdxcheck.py through a couple of self tests to simplify validation in the future. The tests are run for both Python 2 and Python 3 to make sure all changes to the script remain compatible across both versions. The script tests a regular text file (Makefile) for basic sanity checks and then runs it on a binary file (Documentation/logo.gif) to make sure it works in both cases. It also tests opening files passed on the command line as well as piped files read from standard input. Finally a run on the complete tree will be performed to catch any other potential issues. Link: http://lkml.kernel.org/r/20181212131210.28024-2-thierry.reding@gmail.comSigned-off-by:
Thierry Reding <treding@nvidia.com> Thomas Gleixner <tglx@linutronix.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Joe Perches <joe@perches.com> Cc: Jeremy Cline <jcline@redhat.com> Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by:
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Qian Cai authored
This is to track dynamic amount of stack growth for aarch64, so it is possible to print out offensive functions that may consume too much stack. For example, 0xffff2000084d1270 try_to_unmap_one [vmlinux]: Dynamic (0xcf0) 0xffff200008538358 migrate_page_move_mapping [vmlinux]: Dynamic (0xc60) 0xffff2000081276c8 copy_process.isra.2 [vmlinux]: Dynamic (0xb20) 0xffff200008424958 show_free_areas [vmlinux]: Dynamic (0xb40) 0xffff200008545178 __split_huge_pmd_locked [vmlinux]: Dynamic (0xb30) 0xffff200008555120 collapse_shmem [vmlinux]: Dynamic (0xbc0) 0xffff20000862e0d0 do_direct_IO [vmlinux]: Dynamic (0xb70) 0xffff200008cc0aa0 md_do_sync [vmlinux]: Dynamic (0xb90) Link: http://lkml.kernel.org/r/20181208025143.39363-1-cai@lca.pwSigned-off-by:
Qian Cai <cai@lca.pw> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Marc Zyngier authored
Running something like: decodecode vmlinux . leads to interested results where not only the leading "." gets stripped from the displayed paths, but also anywhere in the string, displaying something like: kvm_vcpu_check_block (arch/arm64/kvm/virt/kvm/kvm_mainc:2141) which doesn't help further processing. Fix it by only stripping the base path if it is a prefix of the path. Link: http://lkml.kernel.org/r/20181210174659.31054-3-marc.zyngier@arm.comSigned-off-by:
Marc Zyngier <marc.zyngier@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Marc Zyngier authored
When running decodecode natively on arm64, ARCH is likely not to be set, and we end-up with .4byte instead of .inst when generating the disassembly. Similar effects would occur if running natively on a 32bit ARM platform, although that's even less popular. A simple workaround is to populate ARCH when it is not set and that we're running on an arm/arm64 system. Link: http://lkml.kernel.org/r/20181210174659.31054-2-marc.zyngier@arm.comSigned-off-by:
Will Deacon <will.deacon@arm.com> Signed-off-by:
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Rasmus Villemoes authored
Since __LINE__ is part of the symbol created by __ADDRESSABLE, almost any change causes those symbols to disappear and get reincarnated, e.g. add/remove: 4/4 grow/shrink: 0/3 up/down: 32/-171 (-139) Function old new delta __addressable_tracing_set_default_clock8649 - 8 +8 __addressable_tracer_init_tracefs8631 - 8 +8 __addressable_ftrace_dump8383 - 8 +8 __addressable_clear_boot_tracer8632 - 8 +8 __addressable_tracing_set_default_clock8650 8 - -8 __addressable_tracer_init_tracefs8632 8 - -8 __addressable_ftrace_dump8384 8 - -8 __addressable_clear_boot_tracer8633 8 - -8 trace_default_header 663 642 -21 tracing_mark_raw_write 406 355 -51 tracing_mark_write 624 557 -67 Total: Before=63889, After=63750, chg -0.22% They're small and in .discard, so ignore them, leading to more useful add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-139 (-139) Function old new delta trace_default_header 663 642 -21 tracing_mark_raw_write 406 355 -51 tracing_mark_write 624 557 -67 Total: Before=63721, After=63582, chg -0.22% Link: http://lkml.kernel.org/r/20181102210030.8383-1-linux@rasmusvillemoes.dkSigned-off-by:
Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by:
Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Maninder Singh <maninder1.s@samsung.com> Cc: Matteo Croce <mcroce@redhat.com> Signed-off-by:
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Andrey Konovalov authored
This patch adds a "SPDX-License-Identifier: GPL-2.0" mark to all source files under mm/kasan. Link: http://lkml.kernel.org/r/bce2d1e618afa5142e81961ab8fa4b4165337380.1544099024.git.andreyknvl@google.comSigned-off-by:
Andrey Konovalov <andreyknvl@google.com> Reviewed-by:
Andrey Ryabinin <aryabinin@virtuozzo.com> Reviewed-by:
Dmitry Vyukov <dvyukov@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Andrey Konovalov authored
This patch updates KASAN documentation to reflect the addition of the new tag-based mode. Link: http://lkml.kernel.org/r/aabef9de317c54b8a3919a4946ce534c6576726a.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Now, that all the necessary infrastructure code has been introduced, select HAVE_ARCH_KASAN_SW_TAGS for arm64 to enable software tag-based KASAN mode. Link: http://lkml.kernel.org/r/25abce9a21d0c1df2d9d72488aced418c3465d7b.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
This patch adds __must_check annotations to kasan hooks that return a pointer to make sure that a tagged pointer always gets propagated. Link: http://lkml.kernel.org/r/03b269c5e453945f724bfca3159d4e1333a8fb1c.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Tag-based KASAN doesn't check memory accesses through pointers tagged with 0xff. When page_address is used to get pointer to memory that corresponds to some page, the tag of the resulting pointer gets set to 0xff, even though the allocated memory might have been tagged differently. For slab pages it's impossible to recover the correct tag to return from page_address, since the page might contain multiple slab objects tagged with different values, and we can't know in advance which one of them is going to get accessed. For non slab pages however, we can recover the tag in page_address, since the whole page was marked with the same tag. This patch adds tagging to non slab memory allocated with pagealloc. To set the tag of the pointer returned from page_address, the tag gets stored to page->flags when the memory gets allocated. Link: http://lkml.kernel.org/r/d758ddcef46a5abc9970182b9137e2fbee202a2c.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Tag-based KASAN inline instrumentation mode (which embeds checks of shadow memory into the generated code, instead of inserting a callback) generates a brk instruction when a tag mismatch is detected. This commit adds a tag-based KASAN specific brk handler, that decodes the immediate value passed to the brk instructions (to extract information about the memory access that triggered the mismatch), reads the register values (x0 contains the guilty address) and reports the bug. Link: http://lkml.kernel.org/r/c91fe7684070e34dc34b419e6b69498f4dcacc2d.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
This commit adds tag-based KASAN specific hooks implementation and adjusts common generic and tag-based KASAN ones. 1. When a new slab cache is created, tag-based KASAN rounds up the size of the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16). 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow memory, that corresponds to this object to this tag, and embeds this tag value into the top byte of the returned pointer. 3. On each kfree tag-based KASAN poisons the shadow memory with a random tag to allow detection of use-after-free bugs. The rest of the logic of the hook implementation is very much similar to the one provided by generic KASAN. Tag-based KASAN saves allocation and free stack metadata to the slab object the same way generic KASAN does. Link: http://lkml.kernel.org/r/bda78069e3b8422039794050ddcb2d53d053ed41.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
While with SLUB we can actually preassign tags for caches with contructors and store them in pointers in the freelist, SLAB doesn't allow that since the freelist is stored as an array of indexes, so there are no pointers to store the tags. Instead we compute the tag twice, once when a slab is created before calling the constructor and then again each time when an object is allocated with kmalloc. Tag is computed simply by taking the lowest byte of the index that corresponds to the object. However in kasan_kmalloc we only have access to the objects pointer, so we need a way to find out which index this object corresponds to. This patch moves obj_to_index from slab.c to include/linux/slab_def.h to be reused by KASAN. Link: http://lkml.kernel.org/r/c02cd9e574cfd93858e43ac94b05e38f891fef64.1544099024.git.andreyknvl@google.comSigned-off-by:
Christoph Lameter <cl@linux.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by:
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Andrey Konovalov authored
This commit adds rountines, that print tag-based KASAN error reports. Those are quite similar to generic KASAN, the difference is: 1. The way tag-based KASAN finds the first bad shadow cell (with a mismatching tag). Tag-based KASAN compares memory tags from the shadow memory to the pointer tag. 2. Tag-based KASAN reports all bugs with the "KASAN: invalid-access" header. Also simplify generic KASAN find_first_bad_addr. Link: http://lkml.kernel.org/r/aee6897b1bd077732a315fd84c6b4f234dbfdfcb.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Move generic KASAN specific error reporting routines to generic_report.c without any functional changes, leaving common error reporting code in report.c to be later reused by tag-based KASAN. Link: http://lkml.kernel.org/r/ba48c32f8e5aefedee78998ccff0413bee9e0f5b.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
The krealloc function checks where the same buffer was reused or a new one allocated by comparing kernel pointers. Tag-based KASAN changes memory tag on the krealloc'ed chunk of memory and therefore also changes the pointer tag of the returned pointer. Therefore we need to perform comparison on untagged (with tags reset) pointers to check whether it's the same memory region or not. Link: http://lkml.kernel.org/r/14f6190d7846186a3506cd66d82446646fe65090.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Tag-based KASAN uses the Top Byte Ignore feature of arm64 CPUs to store a pointer tag in the top byte of each pointer. This commit enables the TCR_TBI1 bit, which enables Top Byte Ignore for the kernel, when tag-based KASAN is used. Link: http://lkml.kernel.org/r/f51eca084c8cdb2f3a55195fe342dc8953b7aead.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Right now arm64 fault handling code removes pointer tags from addresses covered by TTBR0 in faults taken from both EL0 and EL1, but doesn't do that for pointers covered by TTBR1. This patch adds two helper functions is_ttbr0_addr() and is_ttbr1_addr(), where the latter one accounts for the fact that TTBR1 pointers might be tagged when tag-based KASAN is in use, and uses these helper functions to perform pointer checks in arch/arm64/mm/fault.c. Link: http://lkml.kernel.org/r/3f349b0e9e48b5df3298a6b4ae0634332274494a.1544099024.git.andreyknvl@google.comSigned-off-by:
Mark Rutland <mark.rutland@arm.com> Acked-by:
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Andrey Konovalov authored
An object constructor can initialize pointers within this objects based on the address of the object. Since the object address might be tagged, we need to assign a tag before calling constructor. The implemented approach is to assign tags to objects with constructors when a slab is allocated and call constructors once as usual. The downside is that such object would always have the same tag when it is reallocated, so we won't catch use-after-frees on it. Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since they can be validy accessed after having been freed. Link: http://lkml.kernel.org/r/f158a8a74a031d66f0a9398a5b0ed453c37ba09a.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
virt_addr_is_linear (which is used by virt_addr_valid) assumes that the top byte of the address is 0xff, which isn't always the case with tag-based KASAN. This patch resets the tag in this macro. Link: http://lkml.kernel.org/r/df73a37dd5ed37f4deaf77bc718e9f2e590e69b1.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
This commit adds a few helper functions, that are meant to be used to work with tags embedded in the top byte of kernel pointers: to set, to get or to reset the top byte. Link: http://lkml.kernel.org/r/f6c6437bb8e143bc44f42c3c259c62e734be7935.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Move the untagged_addr() macro from arch/arm64/include/asm/uaccess.h to arch/arm64/include/asm/memory.h to be later reused by KASAN. Also make the untagged_addr() macro accept all kinds of address types (void *, unsigned long, etc.). This allows not to specify type casts in each place where the macro is used. This is done by using __typeof__. Link: http://lkml.kernel.org/r/2e9ef8d2ed594106eca514b268365b5419113f6a.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
A tag-based KASAN shadow memory cell contains a memory tag, that corresponds to the tag in the top byte of the pointer, that points to that memory. The native top byte value of kernel pointers is 0xff, so with tag-based KASAN we need to initialize shadow memory to 0xff. [cai@lca.pw: arm64: skip kmemleak for KASAN again\ Link: http://lkml.kernel.org/r/20181226020550.63712-1-cai@lca.pw Link: http://lkml.kernel.org/r/5cc1b789aad7c99cf4f3ec5b328b147ad53edb40.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
With tag based KASAN mode the early shadow value is 0xff and not 0x00, so this patch renames kasan_zero_(page|pte|pmd|pud|p4d) to kasan_early_shadow_(page|pte|pmd|pud|p4d) to avoid confusion. Link: http://lkml.kernel.org/r/3fed313280ebf4f88645f5b89ccbc066d320e177.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Tag-based KASAN uses 1 shadow byte for 16 bytes of kernel memory, so it requires 1/16th of the kernel virtual address space for the shadow memory. This commit sets KASAN_SHADOW_SCALE_SHIFT to 4 when the tag-based KASAN mode is enabled. Link: http://lkml.kernel.org/r/308b6bd49f756bb5e533be93c6f085ba99b30339.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
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.comSigned-off-by:
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Andrey Konovalov authored
We now have two KASAN modes: generic KASAN and tag-based KASAN. Rename kasan.c to generic.c to reflect that. Also rename kasan_init.c to init.c as it contains initialization code for both KASAN modes. Link: http://lkml.kernel.org/r/88c6fd2a883e459e6242030497230e5fb0d44d44.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Tag-based KASAN reuses a significant part of the generic KASAN code, so move the common parts to common.c without any functional changes. Link: http://lkml.kernel.org/r/114064d002356e03bb8cc91f7835e20dc61b51d9.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
The previous patch updated KASAN hooks signatures and their usage in SLAB and SLUB code, except for the early_kmem_cache_node_alloc function. This patch handles that function separately, as it requires to reorder some of the initialization code to correctly propagate a tagged pointer in case a tag is assigned by kasan_kmalloc. Link: http://lkml.kernel.org/r/fc8d0fdcf733a7a52e8d0daaa650f4736a57de8c.1544099024.git.andreyknvl@google.comSigned-off-by:
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Andrey Konovalov authored
Patch series "kasan: add software tag-based mode for arm64", v13. This patchset adds a new software tag-based mode to KASAN [1]. (Initially this mode was called KHWASAN, but it got renamed, see the naming rationale at the end of this section). The plan is to implement HWASan [2] for the kernel with the incentive, that it's going to have comparable to KASAN performance, but in the same time consume much less memory, trading that off for somewhat imprecise bug detection and being supported only for arm64. The underlying ideas of the approach used by software tag-based KASAN are: 1. By using the Top Byte Ignore (TBI) arm64 CPU feature, we can store pointer tags in the top byte of each kernel pointer. 2. Using shadow memory, we can store memory tags for each chunk of kernel memory. 3. On each memory allocation, we can generate a random tag, embed it into the returned pointer and set the memory tags that correspond to this chunk of memory to the same value. 4. By using compiler instrumentation, before each memory access we can add a check that the pointer tag matches the tag of the memory that is being accessed. 5. On a tag mismatch we report an error. With this patchset the existing KASAN mode gets renamed to generic KASAN, with the word "generic" meaning that the implementation can be supported by any architecture as it is purely software. The new mode this patchset adds is called software tag-based KASAN. The word "tag-based" refers to the fact that this mode uses tags embedded into the top byte of kernel pointers and the TBI arm64 CPU feature that allows to dereference such pointers. The word "software" here means that shadow memory manipulation and tag checking on pointer dereference is done in software. As it is the only tag-based implementation right now, "software tag-based" KASAN is sometimes referred to as simply "tag-based" in this patchset. A potential expansion of this mode is a hardware tag-based mode, which would use hardware memory tagging support (announced by Arm [3]) instead of compiler instrumentation and manual shadow memory manipulation. Same as generic KASAN, software tag-based KASAN is strictly a debugging feature. [1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html [2] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html [3] https://community.arm.com/processors/b/blog/posts/arm-a-profile-architecture-2018-developments-armv85a ====== Rationale On mobile devices generic KASAN's memory usage is significant problem. One of the main reasons to have tag-based KASAN is to be able to perform a similar set of checks as the generic one does, but with lower memory requirements. Comment from Vishwath Mohan <vishwath@google.com>: I don't have data on-hand, but anecdotally both ASAN and KASAN have proven problematic to enable for environments that don't tolerate the increased memory pressure well. This includes (a) Low-memory form factors - Wear, TV, Things, lower-tier phones like Go, (c) Connected components like Pixel's visual core [1]. These are both places I'd love to have a low(er) memory footprint option at my disposal. Comment from Evgenii Stepanov <eugenis@google.com>: Looking at a live Android device under load, slab (according to /proc/meminfo) + kernel stack take 8-10% available RAM (~350MB). KASAN's overhead of 2x - 3x on top of it is not insignificant. Not having this overhead enables near-production use - ex. running KASAN/KHWASAN kernel on a personal, daily-use device to catch bugs that do not reproduce in test configuration. These are the ones that often cost the most engineering time to track down. CPU overhead is bad, but generally tolerable. RAM is critical, in our experience. Once it gets low enough, OOM-killer makes your life miserable. [1] https://www.blog.google/products/pixel/pixel-visual-core-image-processing-and-machine-learning-pixel-2/ ====== Technical details Software tag-based KASAN mode is implemented in a very similar way to the generic one. This patchset essentially does the following: 1. TCR_TBI1 is set to enable Top Byte Ignore. 2. Shadow memory is used (with a different scale, 1:16, so each shadow byte corresponds to 16 bytes of kernel memory) to store memory tags. 3. All slab objects are aligned to shadow scale, which is 16 bytes. 4. All pointers returned from the slab allocator are tagged with a random tag and the corresponding shadow memory is poisoned with the same value. 5. Compiler instrumentation is used to insert tag checks. Either by calling callbacks or by inlining them (CONFIG_KASAN_OUTLINE and CONFIG_KASAN_INLINE flags are reused). 6. When a tag mismatch is detected in callback instrumentation mode KASAN simply prints a bug report. In case of inline instrumentation, clang inserts a brk instruction, and KASAN has it's own brk handler, which reports the bug. 7. The memory in between slab objects is marked with a reserved tag, and acts as a redzone. 8. When a slab object is freed it's marked with a reserved tag. Bug detection is imprecise for two reasons: 1. We won't catch some small out-of-bounds accesses, that fall into the same shadow cell, as the last byte of a slab object. 2. We only have 1 byte to store tags, which means we have a 1/256 probability of a tag match for an incorrect access (actually even slightly less due to reserved tag values). Despite that there's a particular type of bugs that tag-based KASAN can detect compared to generic KASAN: use-after-free after the object has been allocated by someone else. ====== Testing Some kernel developers voiced a concern that changing the top byte of kernel pointers may lead to subtle bugs that are difficult to discover. To address this concern deliberate testing has been performed. It doesn't seem feasible to do some kind of static checking to find potential issues with pointer tagging, so a dynamic approach was taken. All pointer comparisons/subtractions have been instrumented in an LLVM compiler pass and a kernel module that would print a bug report whenever two pointers with different tags are being compared/subtracted (ignoring comparisons with NULL pointers and with pointers obtained by casting an error code to a pointer type) has been used. Then the kernel has been booted in QEMU and on an Odroid C2 board and syzkaller has been run. This yielded the following results. The two places that look interesting are: is_vmalloc_addr in include/linux/mm.h is_kernel_rodata in mm/util.c Here we compare a pointer with some fixed untagged values to make sure that the pointer lies in a particular part of the kernel address space. Since tag-based KASAN doesn't add tags to pointers that belong to rodata or vmalloc regions, this should work as is. To make sure debug checks to those two functions that check that the result doesn't change whether we operate on pointers with or without untagging has been added. A few other cases that don't look that interesting: Comparing pointers to achieve unique sorting order of pointee objects (e.g. sorting locks addresses before performing a double lock): tty_ldisc_lock_pair_timeout in drivers/tty/tty_ldisc.c pipe_double_lock in fs/pipe.c unix_state_double_lock in net/unix/af_unix.c lock_two_nondirectories in fs/inode.c mutex_lock_double in kernel/events/core.c ep_cmp_ffd in fs/eventpoll.c fsnotify_compare_groups fs/notify/mark.c Nothing needs to be done here, since the tags embedded into pointers don't change, so the sorting order would still be unique. Checks that a pointer belongs to some particular allocation: is_sibling_entry in lib/radix-tree.c object_is_on_stack in include/linux/sched/task_stack.h Nothing needs to be done here either, since two pointers can only belong to the same allocation if they have the same tag. Overall, since the kernel boots and works, there are no critical bugs. As for the rest, the traditional kernel testing way (use until fails) is the only one that looks feasible. Another point here is that tag-based KASAN is available under a separate config option that needs to be deliberately enabled. Even though it might be used in a "near-production" environment to find bugs that are not found during fuzzing or running tests, it is still a debug tool. ====== Benchmarks The following numbers were collected on Odroid C2 board. Both generic and tag-based KASAN were used in inline instrumentation mode. Boot time [1]: * ~1.7 sec for clean kernel * ~5.0 sec for generic KASAN * ~5.0 sec for tag-based KASAN Network performance [2]: * 8.33 Gbits/sec for clean kernel * 3.17 Gbits/sec for generic KASAN * 2.85 Gbits/sec for tag-based KASAN Slab memory usage after boot [3]: * ~40 kb for clean kernel * ~105 kb (~260% overhead) for generic KASAN * ~47 kb (~20% overhead) for tag-based KASAN KASAN memory overhead consists of three main parts: 1. Increased slab memory usage due to redzones. 2. Shadow memory (the whole reserved once during boot). 3. Quaratine (grows gradually until some preset limit; the more the limit, the more the chance to detect a use-after-free). Comparing tag-based vs generic KASAN for each of these points: 1. 20% vs 260% overhead. 2. 1/16th vs 1/8th of physical memory. 3. Tag-based KASAN doesn't require quarantine. [1] Time before the ext4 driver is initialized. [2] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`. [3] Measured as `cat /proc/meminfo | grep Slab`. ====== Some notes A few notes: 1. The patchset can be found here: https://github.com/xairy/kasan-prototype/tree/khwasan 2. Building requires a recent Clang version (7.0.0 or later). 3. Stack instrumentation is not supported yet and will be added later. This patch (of 25): Tag-based KASAN changes the value of the top byte of pointers returned from the kernel allocation functions (such as kmalloc). This patch updates KASAN hooks signatures and their usage in SLAB and SLUB code to reflect that. Link: http://lkml.kernel.org/r/aec2b5e3973781ff8a6bb6760f8543643202c451.1544099024.git.andreyknvl@google.comSigned-off-by:
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git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linuxLinus Torvalds authored
Pull file locking updates from Jeff Layton: "The main change in this set is Neil Brown's work to reduce the thundering herd problem when a heavily-contended file lock is released. Previously we'd always wake up all waiters when this occurred. With this set, we'll now we only wake up waiters that were blocked on the range being released" * tag 'locks-v4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux: locks: Use inode_is_open_for_write fs/locks: remove unnecessary white space. fs/locks: merge posix_unblock_lock() and locks_delete_block() fs/locks: create a tree of dependent requests. fs/locks: change all *_conflict() functions to return bool. fs/locks: always delete_block after waiting. fs/locks: allow a lock request to block other requests. fs/locks: use properly initialized file_lock when unlocking. ocfs2: properly initial file_lock used for unlock. gfs2: properly initial file_lock used for unlock. NFS: use locks_copy_lock() to copy locks. fs/locks: split out __locks_wake_up_blocks(). fs/locks: rename some lists and pointers.
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git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4Linus Torvalds authored
Pull ext4 updates from Ted Ts'o: "All cleanups and bug fixes; most notably, fix some problems discovered in ext4's NFS support, and fix an ioctl (EXT4_IOC_GROUP_ADD) used by old versions of e2fsprogs which we accidentally broke a while back. Also fixed some error paths in ext4's quota and inline data support. Finally, improve tail latency in jbd2's commit code" * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext4: check for shutdown and r/o file system in ext4_write_inode() ext4: force inode writes when nfsd calls commit_metadata() ext4: avoid declaring fs inconsistent due to invalid file handles ext4: include terminating u32 in size of xattr entries when expanding inodes ext4: compare old and new mode before setting update_mode flag ext4: fix EXT4_IOC_GROUP_ADD ioctl ext4: hard fail dax mount on unsupported devices jbd2: update locking documentation for transaction_t ext4: remove redundant condition check jbd2: clean up indentation issue, replace spaces with tab ext4: clean up indentation issues, remove extraneous tabs ext4: missing unlock/put_page() in ext4_try_to_write_inline_data() ext4: fix possible use after free in ext4_quota_enable jbd2: avoid long hold times of j_state_lock while committing a transaction ext4: add ext4_sb_bread() to disambiguate ENOMEM cases
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