WSL2-Linux-Kernel/lib
Daniel Axtens adb72ae191 kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE
Patch series "Fix some incompatibilites between KASAN and FORTIFY_SOURCE", v4.

3 KASAN self-tests fail on a kernel with both KASAN and FORTIFY_SOURCE:
memchr, memcmp and strlen.

When FORTIFY_SOURCE is on, a number of functions are replaced with
fortified versions, which attempt to check the sizes of the operands.
However, these functions often directly invoke __builtin_foo() once they
have performed the fortify check.  The compiler can detect that the
results of these functions are not used, and knows that they have no other
side effects, and so can eliminate them as dead code.

Why are only memchr, memcmp and strlen affected?
================================================

Of string and string-like functions, kasan_test tests:

 * strchr  ->  not affected, no fortified version
 * strrchr ->  likewise
 * strcmp  ->  likewise
 * strncmp ->  likewise

 * strnlen ->  not affected, the fortify source implementation calls the
               underlying strnlen implementation which is instrumented, not
               a builtin

 * strlen  ->  affected, the fortify souce implementation calls a __builtin
               version which the compiler can determine is dead.

 * memchr  ->  likewise
 * memcmp  ->  likewise

 * memset ->   not affected, the compiler knows that memset writes to its
	       first argument and therefore is not dead.

Why does this not affect the functions normally?
================================================

In string.h, these functions are not marked as __pure, so the compiler
cannot know that they do not have side effects.  If relevant functions are
marked as __pure in string.h, we see the following warnings and the
functions are elided:

lib/test_kasan.c: In function `kasan_memchr':
lib/test_kasan.c:606:2: warning: statement with no effect [-Wunused-value]
  memchr(ptr, '1', size + 1);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~
lib/test_kasan.c: In function `kasan_memcmp':
lib/test_kasan.c:622:2: warning: statement with no effect [-Wunused-value]
  memcmp(ptr, arr, size+1);
  ^~~~~~~~~~~~~~~~~~~~~~~~
lib/test_kasan.c: In function `kasan_strings':
lib/test_kasan.c:645:2: warning: statement with no effect [-Wunused-value]
  strchr(ptr, '1');
  ^~~~~~~~~~~~~~~~
...

This annotation would make sense to add and could be added at any point,
so the behaviour of test_kasan.c should change.

The fix
=======

Make all the functions that are pure write their results to a global,
which makes them live.  The strlen and memchr tests now pass.

The memcmp test still fails to trigger, which is addressed in the next
patch.

[dja@axtens.net: drop patch 3]
  Link: http://lkml.kernel.org/r/20200424145521.8203-2-dja@axtens.net
Fixes: 0c96350a2d ("lib/test_kasan.c: add tests for several string/memory API functions")
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: David Gow <davidgow@google.com>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Link: http://lkml.kernel.org/r/20200423154503.5103-1-dja@axtens.net
Link: http://lkml.kernel.org/r/20200423154503.5103-2-dja@axtens.net
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-06-03 20:09:42 -07:00
..
842
crypto crypto: lib/sha1 - remove unnecessary includes of linux/cryptohash.h 2020-05-08 15:32:17 +10:00
dim
fonts
kunit kunit: Add missing newline in summary message 2020-04-23 15:42:00 -06:00
livepatch
lz4
lzo
math
mpi Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-06-01 12:00:10 -07:00
raid6 x86: update AS_* macros to binutils >=2.23, supporting ADX and AVX2 2020-04-09 00:12:48 +09:00
reed_solomon
vdso
xz
zlib_deflate
zlib_dfltcc
zlib_inflate
zstd
.gitignore
Kconfig A fair amount of stuff this time around, dominated by yet another massive 2020-06-01 15:45:27 -07:00
Kconfig.debug hmm related patches for 5.8 2020-06-02 14:05:27 -07:00
Kconfig.kasan
Kconfig.kgdb
Kconfig.ubsan ubsan: entirely disable alignment checks under UBSAN_TRAP 2020-06-02 10:59:12 -07:00
Makefile hmm related patches for 5.8 2020-06-02 14:05:27 -07:00
argv_split.c
ashldi3.c
ashrdi3.c
asn1_decoder.c
assoc_array.c
atomic64.c
atomic64_test.c
audit.c
bcd.c
bch.c lib/bch.c: replace zero-length array with flexible-array member 2020-04-07 10:43:42 -07:00
bitmap.c lib: bitmap.c: get rid of some doc warnings 2020-04-20 15:45:41 -06:00
bitrev.c
bootconfig.c
bsearch.c
btree.c
bucket_locks.c
bug.c
build_OID_registry
bust_spinlocks.c
check_signature.c
checksum.c take the dummy csum_and_copy_from_user() into net/checksum.h 2020-05-29 16:11:50 -04:00
clz_ctz.c
clz_tab.c
cmdline.c
cmpdi2.c
compat_audit.c
cpu_rmap.c
cpumask.c
crc-ccitt.c
crc-itu-t.c
crc-t10dif.c
crc4.c
crc7.c
crc8.c
crc16.c
crc32.c
crc32defs.h
crc32test.c
crc64.c
ctype.c
debug_info.c
debug_locks.c
debugobjects.c
dec_and_lock.c
decompress.c
decompress_bunzip2.c
decompress_inflate.c
decompress_unlz4.c
decompress_unlzma.c
decompress_unlzo.c
decompress_unxz.c
devres.c
digsig.c
dump_stack.c
dynamic_debug.c lib/dynamic_debug.c: use address-of operator on section symbols 2020-04-07 10:43:43 -07:00
dynamic_queue_limits.c
earlycpio.c
errname.c
error-inject.c
errseq.c
extable.c
fault-inject.c
fdt.c
fdt_addresses.c
fdt_empty_tree.c
fdt_ro.c
fdt_rw.c
fdt_strerror.c
fdt_sw.c
fdt_wip.c
find_bit.c
find_bit_benchmark.c
flex_proportions.c
gen_crc32table.c
gen_crc64table.c
genalloc.c
generic-radix-tree.c
glob.c
globtest.c
hexdump.c
hweight.c
idr.c
inflate.c
interval_tree.c
interval_tree_test.c
iomap.c
iomap_copy.c
iommu-helper.c
ioremap.c mm/ioremap: track which page-table levels were modified 2020-06-02 10:59:11 -07:00
iov_iter.c
irq_poll.c
irq_regs.c
is_single_threaded.c
kasprintf.c
kfifo.c
klist.c
kobject.c docs: filesystems: fix renamed references 2020-04-20 15:45:22 -06:00
kobject_uevent.c
kstrtox.c
kstrtox.h
libcrc32c.c
linear_ranges.c lib: linear_ranges: Add missing MODULE_LICENSE() 2020-05-11 11:55:28 +01:00
list-test.c
list_debug.c
list_sort.c
llist.c
locking-selftest-hardirq.h
locking-selftest-mutex.h
locking-selftest-rlock-hardirq.h
locking-selftest-rlock-softirq.h
locking-selftest-rlock.h
locking-selftest-rsem.h
locking-selftest-rtmutex.h
locking-selftest-softirq.h
locking-selftest-spin-hardirq.h
locking-selftest-spin-softirq.h
locking-selftest-spin.h
locking-selftest-wlock-hardirq.h
locking-selftest-wlock-softirq.h
locking-selftest-wlock.h
locking-selftest-wsem.h
locking-selftest.c
lockref.c
logic_pio.c
lru_cache.c
lshrdi3.c
memcat_p.c
memory-notifier-error-inject.c
memregion.c
memweight.c
muldi3.c
net_utils.c
netdev-notifier-error-inject.c
nlattr.c
nmi_backtrace.c
nodemask.c
notifier-error-inject.c
notifier-error-inject.h
objagg.c
of-reconfig-notifier-error-inject.c
oid_registry.c
once.c
packing.c
parman.c
parser.c
pci_iomap.c
percpu-refcount.c
percpu_counter.c
percpu_test.c
plist.c
pm-notifier-error-inject.c
radix-tree.c radix-tree: Use local_lock for protection 2020-05-28 10:31:09 +02:00
random32.c
ratelimit.c
rbtree.c lib/rbtree: fix coding style of assignments 2020-04-07 10:43:43 -07:00
rbtree_test.c
refcount.c
rhashtable.c
sbitmap.c
scatterlist.c lib/scatterlist: fix sg_copy_buffer() kerneldoc 2020-04-07 10:43:43 -07:00
seq_buf.c
sg_pool.c
sg_split.c
sha1.c crypto: lib/sha1 - fold linux/cryptohash.h into crypto/sha.h 2020-05-08 15:32:17 +10:00
show_mem.c
siphash.c
smp_processor_id.c
sort.c
stackdepot.c kasan: stackdepot: move filter_irq_stacks() to stackdepot.c 2020-04-07 10:43:43 -07:00
stmp_device.c
string.c
string_helpers.c
strncpy_from_user.c uaccess: Selectively open read or write user access 2020-05-01 12:35:21 +10:00
strnlen_user.c uaccess: Selectively open read or write user access 2020-05-01 12:35:21 +10:00
syscall.c
test-kstrtox.c
test-string_helpers.c
test_bitfield.c
test_bitmap.c lib/test_bitmap.c: make use of EXP2_IN_BITS 2020-04-07 10:43:43 -07:00
test_blackhole_dev.c
test_bpf.c
test_debug_virtual.c
test_firmware.c
test_hash.c
test_hexdump.c
test_hmm.c mm/hmm/test: add selftest driver for HMM 2020-05-19 16:48:30 -03:00
test_hmm_uapi.h mm/hmm/test: add selftest driver for HMM 2020-05-19 16:48:30 -03:00
test_ida.c
test_kasan.c kasan: stop tests being eliminated as dead code with FORTIFY_SOURCE 2020-06-03 20:09:42 -07:00
test_kmod.c lib/test_kmod.c: remove a NULL test 2020-04-07 10:43:43 -07:00
test_linear_ranges.c lib/test_linear_ranges: add a test for the 'linear_ranges' 2020-05-08 18:18:12 +01:00
test_list_sort.c
test_lockup.c lib/test_lockup.c: add parameters for locking generic vfs locks 2020-04-07 10:43:42 -07:00
test_memcat_p.c
test_meminit.c
test_min_heap.c
test_module.c
test_objagg.c
test_overflow.c
test_parman.c
test_printf.c Printk changes for 5.8 2020-06-01 12:13:30 -07:00
test_rhashtable.c
test_siphash.c
test_sort.c
test_stackinit.c lib: test_stackinit.c: XFAIL switch variable init tests 2020-04-07 10:43:43 -07:00
test_static_key_base.c
test_static_keys.c
test_string.c
test_strscpy.c
test_sysctl.c
test_ubsan.c
test_user_copy.c
test_uuid.c
test_vmalloc.c mm: switch the test_vmalloc module to use __vmalloc_node 2020-06-02 10:59:11 -07:00
test_xarray.c
textsearch.c
timerqueue.c
ts_bm.c lib/ts_bm.c: replace zero-length array with flexible-array member 2020-04-07 10:43:42 -07:00
ts_fsm.c lib/ts_fsm.c: replace zero-length array with flexible-array member 2020-04-07 10:43:43 -07:00
ts_kmp.c lib/ts_kmp.c: replace zero-length array with flexible-array member 2020-04-07 10:43:43 -07:00
ubsan.c ubsan: include bug type in report header 2020-04-07 10:43:44 -07:00
ubsan.h
ucmpdi2.c
ucs2_string.c
usercopy.c uaccess: Selectively open read or write user access 2020-05-01 12:35:21 +10:00
uuid.c
vsprintf.c Printk changes for 5.8 2020-06-01 12:13:30 -07:00
win_minmax.c
xarray.c
xxhash.c