Dmitry Vyukov 2cf12f821c lib/llist.c: fix data race in llist_del_first ... llist_del_first reads entry->next, but it did not acquire visibility over the entry node. As the result it can get a stale value of entry->next (e.g. NULL or whatever garbage was there before the appending thread wrote correct value). And then commit that value as llist head with cmpxchg. That will corrupt llist. Note there is a control-dependency between read of head->first and read of entry->next, but it does not make the code correct. Kernel memory model unambiguously says: "A load-load control dependency requires a full read memory barrier". Use smp_load_acquire to acquire visibility over the entry node. The data race was found with KernelThreadSanitizer (KTSAN). Here is an example of KTSAN report: ThreadSanitizer: data-race in llist_del_first Read of size 1 by thread T389 (K2630, CPU0): [<ffffffff8156b8a9>] llist_del_first+0x39/0x70 lib/llist.c:74 [< inlined >] tty_buffer_alloc drivers/tty/tty_buffer.c:181 [<ffffffff81664af4>] __tty_buffer_request_room+0xb4/0x250 drivers/tty/tty_buffer.c:292 [<ffffffff81664e6c>] tty_insert_flip_string_fixed_flag+0x6c/0x150 drivers/tty/tty_buffer.c:337 [< inlined >] tty_insert_flip_string include/linux/tty_flip.h:35 [<ffffffff81667422>] pty_write+0x72/0xc0 drivers/tty/pty.c:110 [< inlined >] process_output_block drivers/tty/n_tty.c:611 [<ffffffff8165c016>] n_tty_write+0x346/0x7f0 drivers/tty/n_tty.c:2401 [< inlined >] do_tty_write drivers/tty/tty_io.c:1159 [<ffffffff816568df>] tty_write+0x21f/0x3f0 drivers/tty/tty_io.c:1245 [<ffffffff8125f00f>] __vfs_write+0x5f/0x1f0 fs/read_write.c:489 [<ffffffff8125ff8f>] vfs_write+0xef/0x280 fs/read_write.c:538 [< inlined >] SYSC_write fs/read_write.c:585 [<ffffffff81261390>] SyS_write+0x70/0xe0 fs/read_write.c:577 [<ffffffff81ee862e>] entry_SYSCALL_64_fastpath+0x12/0x71 arch/x86/entry/entry_64.S:186 Previous write of size 8 by thread T226 (K761, CPU0): [<ffffffff8156b832>] llist_add_batch+0x32/0x70 lib/llist.c:44 (discriminator 16) [< inlined >] llist_add include/linux/llist.h:180 [<ffffffff816649fc>] tty_buffer_free+0x6c/0xb0 drivers/tty/tty_buffer.c:221 [<ffffffff816651e7>] flush_to_ldisc+0x107/0x300 drivers/tty/tty_buffer.c:514 [<ffffffff810b20ee>] process_one_work+0x47e/0x930 kernel/workqueue.c:2036 [<ffffffff810b2650>] worker_thread+0xb0/0x900 kernel/workqueue.c:2170 [<ffffffff810bbe20>] kthread+0x150/0x170 kernel/kthread.c:209 [<ffffffff81ee8a1f>] ret_from_fork+0x3f/0x70 arch/x86/entry/entry_64.S:526 Signed-off-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Huang Ying <ying.huang@intel.com> Cc: Konstantin Serebryany <kcc@google.com> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2015-11-06 17:50:42 -08:00
..
842
fonts
lz4
lzo
mpi
raid6
reed_solomon
xz
zlib_deflate
zlib_inflate
.gitignore
argv_split.c
asn1_decoder.c
assoc_array.c
atomic64.c
atomic64_test.c
audit.c
bcd.c
bch.c
bitmap.c
bitrev.c
bsearch.c
btree.c
bug.c
build_OID_registry
bust_spinlocks.c
check_signature.c
checksum.c
clz_ctz.c
clz_tab.c
cmdline.c
compat_audit.c
cordic.c
cpu-notifier-error-inject.c
cpu_rmap.c
cpumask.c
crc-ccitt.c
crc-itu-t.c
crc-t10dif.c
crc7.c
crc8.c
crc16.c
crc32.c
crc32defs.h
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
div64.c
dma-debug.c
dump_stack.c
dynamic_debug.c	lib/dynamic_debug.c: use kstrdup_const	2015-11-06 17:50:42 -08:00
dynamic_queue_limits.c
earlycpio.c
extable.c
fault-inject.c
fdt.c
fdt_empty_tree.c
fdt_ro.c
fdt_rw.c
fdt_strerror.c
fdt_sw.c
fdt_wip.c
find_bit.c
flex_array.c
flex_proportions.c
gcd.c
gen_crc32table.c
genalloc.c
glob.c
halfmd4.c	lib/halfmd4.c: use rol32 inline function in the ROUND macro	2015-11-06 17:50:42 -08:00
hexdump.c
hweight.c
idr.c	mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd	2015-11-06 17:50:42 -08:00
inflate.c
int_sqrt.c
interval_tree.c
interval_tree_test.c
iomap.c
iomap_copy.c
iommu-common.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc	2015-11-05 16:34:48 -08:00
iommu-helper.c
ioremap.c
iov_iter.c
irq_regs.c
is_single_threaded.c
jedec_ddr_data.c
kasprintf.c
Kconfig
Kconfig.debug	test_printf: test printf family at runtime	2015-11-06 17:50:42 -08:00
Kconfig.kasan	mm, slub, kasan: enable user tracking by default with KASAN=y	2015-11-05 19:34:48 -08:00
Kconfig.kgdb
Kconfig.kmemcheck
kfifo.c
klist.c
kobject.c
kobject_uevent.c
kstrtox.c
kstrtox.h
lcm.c
libcrc32c.c
list_debug.c
list_sort.c
llist.c	lib/llist.c: fix data race in llist_del_first	2015-11-06 17:50:42 -08:00
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-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
lru_cache.c
Makefile	test_printf: test printf family at runtime	2015-11-06 17:50:42 -08:00
md5.c
memory-notifier-error-inject.c
memweight.c
net_utils.c
nlattr.c
nmi_backtrace.c
notifier-error-inject.c
notifier-error-inject.h
of-reconfig-notifier-error-inject.c
oid_registry.c
once.c
parser.c
pci_iomap.c
percpu-refcount.c
percpu_counter.c
percpu_ida.c	mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM	2015-11-06 17:50:42 -08:00
percpu_test.c
plist.c
pm-notifier-error-inject.c
proportions.c
radix-tree.c	mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd	2015-11-06 17:50:42 -08:00
random32.c
ratelimit.c
rational.c
rbtree.c
rbtree_test.c
reciprocal_div.c
rhashtable.c
scatterlist.c
seq_buf.c
sg_split.c
sha1.c
show_mem.c
smp_processor_id.c
sort.c
stmp_device.c
string.c
string_helpers.c
strncpy_from_user.c
strnlen_user.c
swiotlb.c
syscall.c
test-hexdump.c
test-kstrtox.c
test-string_helpers.c	lib/test-string_helpers.c: add string_get_size() tests	2015-11-06 17:50:42 -08:00
test_bpf.c
test_firmware.c
test_kasan.c	lib: test_kasan: add some testcases	2015-11-05 19:34:48 -08:00
test_module.c
test_printf.c	test_printf: test printf family at runtime	2015-11-06 17:50:42 -08:00
test_rhashtable.c
test_static_key_base.c
test_static_keys.c
test_user_copy.c
textsearch.c
timerqueue.c
ts_bm.c
ts_fsm.c
ts_kmp.c
ucs2_string.c
usercopy.c
uuid.c
vsprintf.c	lib/vsprintf.c: update documentation	2015-11-06 17:50:42 -08:00