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Now that %z is standartised in C99 there is no reason to support %Z.
Unlike %L it doesn't even make format strings smaller.
Use BUILD_BUG_ON in a couple ATM drivers.
In case anyone didn't notice lib/vsprintf.o is about half of SLUB which is
in my opinion is quite an achievement. Hopefully this patch inspires
someone else to trim vsprintf.c more.
Link: http://lkml.kernel.org/r/20170103230126.GA30170@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The existing test was only exercising native unsigned long size
get_user(). For completeness, we should check all sizes. But we
must skip some 32-bit architectures that don't implement a 64-bit
get_user().
Signed-off-by: Kees Cook <keescook@chromium.org>
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Under SMAP/PAN/etc, we cannot write directly to userspace memory, so
this rearranges the test bytes to get written through copy_to_user().
Additionally drops the bad copy_from_user() test that would trigger a
memcpy() against userspace on failure.
Signed-off-by: Kees Cook <keescook@chromium.org>
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During usercopy the destination buffer will be zeroed if copy_from_user()
or get_user() fails. This patch adds testcases for it. The destination
buffer is set with non-zero value before illegal copy_from_user() or
get_user() is executed and the buffer is compared to zero after usercopy
is done.
Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com>
[kees: clarified commit log, dropped second kmalloc]
Signed-off-by: Kees Cook <keescook@chromium.org>
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It will be used in drivers/md/raid5-cache.c
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
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The address sanitizer occasionally finds an out of bounds error while
running the test-suite. It turned out to be a read of the pointer
immediately next to the tree root, but this out of bounds error could
have occurred elsewhere. This happens because radix_tree_iter_resume()
dereferences 'slot' before checking whether we've come to the end of
the chunk. We can just delete this line; the value was never used.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
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Instead of having this mysterious private_data in each radix_tree_node,
store a pointer to the root, which can be useful for debugging. This also
relieves the mm code from the duty of updating it.
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
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Chaining through the ->private_data member means we have to zero
->private_data after removing preallocated nodes from the list.
We're about to initialise ->parent anyway, so we can avoid zeroing it.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
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We can use the root entry as a bitmap and save allocating a 128 byte
bitmap for an IDA that contains only a few entries (30 on a 32-bit
machine, 62 on a 64-bit machine). This costs about 300 bytes of kernel
text on x86-64, so as long as 3 IDAs fall into this category, this
is a net win for memory consumption.
Thanks to Rasmus Villemoes for his work documenting the problem and
collecting statistics on IDAs.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
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When we preload the IDA, we allocate an IDA bitmap. Instead of storing
that preallocated bitmap in the IDA, we store it in a percpu variable.
Generally there are more IDAs in the system than CPUs, so this cuts down
on the number of preallocated bitmaps that are unused, and about half
of the IDA users did not call ida_destroy() so they were leaking IDA
bitmaps.
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
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The IDR is very similar to the radix tree. It has some functionality that
the radix tree did not have (alloc next free, cyclic allocation, a
callback-based for_each, destroy tree), which is readily implementable on
top of the radix tree. A few small changes were needed in order to use a
tag to represent nodes with free space below them. More extensive
changes were needed to support storing NULL as a valid entry in an IDR.
Plain radix trees still interpret NULL as a not-present entry.
The IDA is reimplemented as a client of the newly enhanced radix tree. As
in the current implementation, it uses a bitmap at the last level of the
tree.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Currently CONFIG_TIMER_STATS exposes process information across namespaces:
kernel/time/timer_list.c print_timer():
SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);
/proc/timer_list:
#11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570
Given that the tracer can give the same information, this patch entirely
removes CONFIG_TIMER_STATS.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: linux-doc@vger.kernel.org
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Xing Gao <xgao01@email.wm.edu>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jessica Frazelle <me@jessfraz.com>
Cc: kernel-hardening@lists.openwall.com
Cc: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Michal Marek <mmarek@suse.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-api@vger.kernel.org
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/20170208192659.GA32582@beast
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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As suggested by Ingo, the debug_objects_alloc counter is now renamed to
debug_objects_allocated with minor twist in comment and debug output.
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1486503630-1501-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Provide refcount_t, an atomic_t like primitive built just for
refcounting.
It provides saturation semantics such that overflow becomes impossible
and thereby 'spurious' use-after-free is avoided.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Commit 50bed2e2862a ("sg: disable interrupts inside sg_copy_buffer")
introduced disabling interrupts in sg_copy_buffer() since atomic uses of
miter required it due to use of kmap_atomic().
However, as commit 8290e2d2dcbf ("scatterlist: atomic sg_mapping_iter() no
longer needs disabled IRQs") acknowledges disabling interrupts is no
longer needed for calls to kmap_atomic() and therefore unneeded for miter
ops either, so remove it from sg_copy_buffer().
Link: http://lkml.kernel.org/r/1486040150-14109-3-git-send-email-gilad@benyossef.com
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <ofir.drang@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Test the cheaper boolean expression with no side effects first.
Link: http://lkml.kernel.org/r/1486040150-14109-2-git-send-email-gilad@benyossef.com
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <ofir.drang@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Keep fonts together and indented (in menu) as much as possible.
This moves the Sparc font choices to the end of the menu since they
have different dependencies.
Link: http://lkml.kernel.org/r/de6d8977-c6d6-a82d-c953-f2a2fefdb8a5@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Remove the functions introduced as wrappers for providing backwards
compatibility to the prior LZ4 version. They're not needed anymore since
there's no callers left.
Link: http://lkml.kernel.org/r/1486321748-19085-6-git-send-email-4sschmid@informatik.uni-hamburg.de
Signed-off-by: Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
Cc: Bongkyu Kim <bongkyu.kim@lge.com>
Cc: Rui Salvaterra <rsalvaterra@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Update the unlz4 wrapper to work with the updated LZ4 kernel module
version.
Link: http://lkml.kernel.org/r/1486321748-19085-3-git-send-email-4sschmid@informatik.uni-hamburg.de
Signed-off-by: Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
Cc: Bongkyu Kim <bongkyu.kim@lge.com>
Cc: Rui Salvaterra <rsalvaterra@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "Update LZ4 compressor module", v7.
This patchset updates the LZ4 compression module to a version based on LZ4
v1.7.3 allowing to use the fast compression algorithm aka LZ4 fast which
provides an "acceleration" parameter as a tradeoff between high
compression ratio and high compression speed.
We want to use LZ4 fast in order to support compression in lustre and
(mostly, based on that) investigate data reduction techniques in behalf of
storage systems.
Also, it will be useful for other users of LZ4 compression, as with LZ4
fast it is possible to enable applications to use fast and/or high
compression depending on the usecase. For instance, ZRAM is offering a
LZ4 backend and could benefit from an updated LZ4 in the kernel.
LZ4 homepage: http://www.lz4.org/
LZ4 source repository: https://github.com/lz4/lz4 Source version: 1.7.3
Benchmark (taken from [1], Core i5-4300U @1.9GHz):
----------------|--------------|----------------|----------
Compressor | Compression | Decompression | Ratio
----------------|--------------|----------------|----------
memcpy | 4200 MB/s | 4200 MB/s | 1.000
LZ4 fast 50 | 1080 MB/s | 2650 MB/s | 1.375
LZ4 fast 17 | 680 MB/s | 2220 MB/s | 1.607
LZ4 fast 5 | 475 MB/s | 1920 MB/s | 1.886
LZ4 default | 385 MB/s | 1850 MB/s | 2.101
[1] http://fastcompression.blogspot.de/2015/04/sampling-or-faster-lz4.html
[PATCH 1/5] lib: Update LZ4 compressor module
[PATCH 2/5] lib/decompress_unlz4: Change module to work with new LZ4 module version
[PATCH 3/5] crypto: Change LZ4 modules to work with new LZ4 module version
[PATCH 4/5] fs/pstore: fs/squashfs: Change usage of LZ4 to work with new LZ4 version
[PATCH 5/5] lib/lz4: Remove back-compat wrappers
This patch (of 5):
Update the LZ4 kernel module to LZ4 v1.7.3 by Yann Collet. The kernel
module is inspired by the previous work by Chanho Min. The updated LZ4
module will not break existing code since the patchset contains
appropriate changes.
API changes:
New method LZ4_compress_fast which differs from the variant available in
kernel by the new acceleration parameter, allowing to trade compression
ratio for more compression speed and vice versa.
LZ4_decompress_fast is the respective decompression method, featuring a
very fast decoder (multiple GB/s per core), able to reach RAM speed in
multi-core systems. The decompressor allows to decompress data compressed
with LZ4 fast as well as the LZ4 HC (high compression) algorithm.
Also the useful functions LZ4_decompress_safe_partial and
LZ4_compress_destsize were added. The latter reverses the logic by trying
to compress as much data as possible from source to dest while the former
aims to decompress partial blocks of data.
A bunch of streaming functions were also added which allow
compressig/decompressing data in multiple steps (so called "streaming
mode").
The methods lz4_compress and lz4_decompress_unknownoutputsize are now
known as LZ4_compress_default respectivley LZ4_decompress_safe. The old
methods will be removed since there's no callers left in the code.
Link: http://lkml.kernel.org/r/1486321748-19085-2-git-send-email-4sschmid@informatik.uni-hamburg.de
Signed-off-by: Sven Schmidt <4sschmid@informatik.uni-hamburg.de>
Cc: Bongkyu Kim <bongkyu.kim@lge.com>
Cc: Rui Salvaterra <rsalvaterra@gmail.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David S. Miller <davem@davemloft.net>
Cc: Anton Vorontsov <anton@enomsg.org>
Cc: Colin Cross <ccross@android.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The Kconfig currently controlling compilation of this code is:
lib/Kconfig.debug:config TEST_SORT
lib/Kconfig.debug: bool "Array-based sort test"
...meaning that it currently is not being built as a module by anyone.
Lets remove the couple traces of modular infrastructure use, so that
when reading the code there is no doubt it is builtin-only.
Since module_init translates to device_initcall in the non-modular
case, the init ordering becomes slightly earlier when we change it
to use subsys_initcall as done here. However, since it is a self
contained test, this shouldn't be an issue and subsys_initcall
seems like a better fit for this particular case.
We also delete the MODULE_LICENSE tag since that information is now
contained at the top of the file in the comments.
Link: http://lkml.kernel.org/r/20170124225608.7319-1-paul.gortmaker@windriver.com
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Kostenzer Felix <fkostenzer@live.at>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The lib/sort.c file gets included in the EFI stub for use outside of the
kernel address space, which now fails due to the addition of a
module_init() function:
00000000 R_ARM_ABS32 test_sort_init
drivers/firmware/efi/libstub/lib-sort.stub.o: absolute symbol references not allowed in the EFI stub
drivers/firmware/efi/libstub/Makefile:69: recipe for target 'drivers/firmware/efi/libstub/lib-sort.stub.o' failed
Other library tests live in a separate file, so doing the same here
is an easy way to avoid the problem.
Fixes: akpm-current ("lib: add CONFIG_TEST_SORT to enable self-test of sort()")
Link: http://lkml.kernel.org/r/20170112110657.3123790-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Kostenzer Felix <fkostenzer@live.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Along with the addition made to Kconfig.debug, the prior existing but
permanently disabled test function has been slightly refactored.
Patch has been tested using QEMU 2.1.2 with a .config obtained through
'make defconfig' (x86_64) and manually enabling the option.
Link: http://lkml.kernel.org/r/HE1PR09MB0394B0418D504DCD27167D4FD49B0@HE1PR09MB0394.eurprd09.prod.outlook.com
Signed-off-by: Kostenzer Felix <fkostenzer@live.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Prepare to mark sensitive kernel structures for randomization by making
sure they're using designated initializers. These were identified during
allyesconfig builds of x86, arm, and arm64, with most initializer fixes
extracted from grsecurity.
Link: http://lkml.kernel.org/r/20161217010253.GA140470@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Jie Chen <fykcee1@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Link: http://lkml.kernel.org/r/1483709016-1834-1-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Yury Norov <ynorov@caviumnetworks.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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This saves 32 bytes on my x86-64 build, mostly due to alignment
considerations and sharing more code between find_next_bit and
find_next_zero_bit, but it does save a couple of instructions.
There's really two parts to this commit. First, the first half of the
test: (!nbits || start >= nbits) is trivially a subset of the second half,
since nbits and start are both unsigned. Second, while looking at the
disassembly, I noticed that GCC was predicting the branch taken. Since
this is a failure case, it's clearly the less likely of the two branches,
so add an unlikely() to override GCC's heuristics.
Link: http://lkml.kernel.org/r/1483709016-1834-1-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Yury Norov <ynorov@caviumnetworks.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Allow to compile the atomic64 test code either to a loadable module, or
builtin into the kernel.
Link: http://lkml.kernel.org/r/1483470276-10517-3-git-send-email-geert@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Extract the glob test code into its own source file, to allow to
compile it either to a loadable module, or builtin into the kernel.
Link: http://lkml.kernel.org/r/1483470276-10517-2-git-send-email-geert@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Extract the crc32 test code into its own source file, to allow to
compile it either to a loadable module, or builtin into the kernel.
Link: http://lkml.kernel.org/r/1483470276-10517-1-git-send-email-geert@linux-m68k.org
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The CHECK_DATA_CORRUPTION() macro was designed to have callers do
something meaningful/protective on failure. However, using "return false"
in the macro too strictly limits the design patterns of callers. Instead,
let callers handle the logic test directly, but make sure that the result
IS checked by forcing __must_check (which appears to not be able to be
used directly on macro expressions).
Link: http://lkml.kernel.org/r/20170206204547.GA125312@beast
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Make a kasan test which uses a SLAB_ACCOUNT slab cache. If the test is
run within a non default memcg, then it uncovers the bug fixed by
"kasan: drain quarantine of memcg slab objects"[1].
If run without fix [1] it shows "Slab cache still has objects", and the
kmem_cache structure is leaked.
Here's an unpatched kernel test:
$ dmesg -c > /dev/null
$ mkdir /sys/fs/cgroup/memory/test
$ echo $$ > /sys/fs/cgroup/memory/test/tasks
$ modprobe test_kasan 2> /dev/null
$ dmesg | grep -B1 still
[ 123.456789] kasan test: memcg_accounted_kmem_cache allocate memcg accounted object
[ 124.456789] kmem_cache_destroy test_cache: Slab cache still has objects
Kernels with fix [1] don't have the "Slab cache still has objects"
warning or the underlying leak.
The new test runs and passes in the default (root) memcg, though in the
root memcg it won't uncover the problem fixed by [1].
Link: http://lkml.kernel.org/r/1482257462-36948-2-git-send-email-gthelen@google.com
Signed-off-by: Greg Thelen <gthelen@google.com>
Reviewed-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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show_mem() allows to filter out node specific data which is irrelevant to
the allocation request via SHOW_MEM_FILTER_NODES. The filtering is done
in skip_free_areas_node which skips all nodes which are not in the
mems_allowed of the current process. This works most of the time as
expected because the nodemask shouldn't be outside of the allocating task
but there are some exceptions. E.g. memory hotplug might want to request
allocations from outside of the allowed nodes (see new_node_page).
Get rid of this hardcoded behavior and push the allocation mask down the
show_mem path and use it instead of cpuset_current_mems_allowed. NULL
nodemask is interpreted as cpuset_current_mems_allowed.
Link: http://lkml.kernel.org/r/20170117091543.25850-5-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Add comment for failure to check a map error to help driver developers.
Link: http://lkml.kernel.org/r/1484622289-22085-1-git-send-email-miles.chen@mediatek.com
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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When called with a region of contiguous pages totaling > 4 GB of memory,
sg_alloc_table_from_pages() will overflow the length field, leading to a
corrupt scatter list. Fix this by tracking the number of pages we've
merged and start a new chunk when we would overflow.
Tested by building various page lists with contiguous 8GB regions and
observing that they are correctly split without overflowing length.
This isn't from normal read/write IO -- some applications want to
access large amounts of userspace memory directly from hardware, and it
is cleaner for them to manage one mapping than multiple 1GB or 2GB
mappings -- assuming the hardware can even support multiple mappings.
If they have room in their container to allocate and pin the memory,
we'd like to allow it.
There's definitely potential for problems downstream, even without
going through the filesystems and block layers -- we noticed this
potential issue while tracking down an bug in the IOMMU code when an
entry in the list was over 1GB. We still see a benefit from building
the large entries, though -- it allows superpages in the IOMMU mapping
which helps the IOTLB cache.
We currently use sg_alloc_table_from_pages() to build the scatterlist
for dma_map_sg() but we could do it ourselves if you'd rather add a
length limit to the more general code.
Link: http://lkml.kernel.org/r/20170201212917.11278-1-dillow@google.com
Signed-off-by: David Dillow <dillow@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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