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Josef Bacik dc2b77642e nbd: handle device refs for DESTROY_ON_DISCONNECT properly commit `c9a2f90f4d` upstream. There exists a race where we can be attempting to create a new nbd configuration while a previous configuration is going down, both configured with DESTROY_ON_DISCONNECT. Normally devices all have a reference of 1, as they won't be cleaned up until the module is torn down. However with DESTROY_ON_DISCONNECT we'll make sure that there is only 1 reference (generally) on the device for the config itself, and then once the config is dropped, the device is torn down. The race that exists looks like this TASK1 TASK2 nbd_genl_connect() idr_find() refcount_inc_not_zero(nbd) * count is 2 here ^^ nbd_config_put() nbd_put(nbd) (count is 1) setup new config check DESTROY_ON_DISCONNECT put_dev = true if (put_dev) nbd_put(nbd) * free'd here ^^ In nbd_genl_connect() we assume that the nbd ref count will be 2, however clearly that won't be true if the nbd device had been setup as DESTROY_ON_DISCONNECT with its prior configuration. Fix this by getting rid of the runtime flag to check if we need to mess with the nbd device refcount, and use the device NBD_DESTROY_ON_DISCONNECT flag to check if we need to adjust the ref counts. This was reported by syzkaller with the following kasan dump BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline] BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:27 [inline] BUG: KASAN: use-after-free in refcount_dec_not_one+0x71/0x1e0 lib/refcount.c:76 Read of size 4 at addr ffff888143bf71a0 by task systemd-udevd/8451 CPU: 0 PID: 8451 Comm: systemd-udevd Not tainted 5.11.0-rc7-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x107/0x163 lib/dump_stack.c:120 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230 __kasan_report mm/kasan/report.c:396 [inline] kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413 check_memory_region_inline mm/kasan/generic.c:179 [inline] check_memory_region+0x13d/0x180 mm/kasan/generic.c:185 instrument_atomic_read include/linux/instrumented.h:71 [inline] atomic_read include/asm-generic/atomic-instrumented.h:27 [inline] refcount_dec_not_one+0x71/0x1e0 lib/refcount.c:76 refcount_dec_and_mutex_lock+0x19/0x140 lib/refcount.c:115 nbd_put drivers/block/nbd.c:248 [inline] nbd_release+0x116/0x190 drivers/block/nbd.c:1508 __blkdev_put+0x548/0x800 fs/block_dev.c:1579 blkdev_put+0x92/0x570 fs/block_dev.c:1632 blkdev_close+0x8c/0xb0 fs/block_dev.c:1640 __fput+0x283/0x920 fs/file_table.c:280 task_work_run+0xdd/0x190 kernel/task_work.c:140 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline] syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fc1e92b5270 Code: 73 01 c3 48 8b 0d 38 7d 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 59 c1 20 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ee fb ff ff 48 89 04 24 RSP: 002b:00007ffe8beb2d18 EFLAGS: 00000246 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00007fc1e92b5270 RDX: 000000000aba9500 RSI: 0000000000000000 RDI: 0000000000000007 RBP: 00007fc1ea16f710 R08: 000000000000004a R09: 0000000000000008 R10: 0000562f8cb0b2a8 R11: 0000000000000246 R12: 0000000000000000 R13: 0000562f8cb0afd0 R14: 0000000000000003 R15: 000000000000000e Allocated by task 1: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track mm/kasan/common.c:46 [inline] set_alloc_info mm/kasan/common.c:401 [inline] ____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429 kmalloc include/linux/slab.h:552 [inline] kzalloc include/linux/slab.h:682 [inline] nbd_dev_add+0x44/0x8e0 drivers/block/nbd.c:1673 nbd_init+0x250/0x271 drivers/block/nbd.c:2394 do_one_initcall+0x103/0x650 init/main.c:1223 do_initcall_level init/main.c:1296 [inline] do_initcalls init/main.c:1312 [inline] do_basic_setup init/main.c:1332 [inline] kernel_init_freeable+0x605/0x689 init/main.c:1533 kernel_init+0xd/0x1b8 init/main.c:1421 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 Freed by task 8451: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:356 ____kasan_slab_free+0xe1/0x110 mm/kasan/common.c:362 kasan_slab_free include/linux/kasan.h:192 [inline] slab_free_hook mm/slub.c:1547 [inline] slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1580 slab_free mm/slub.c:3143 [inline] kfree+0xdb/0x3b0 mm/slub.c:4139 nbd_dev_remove drivers/block/nbd.c:243 [inline] nbd_put.part.0+0x180/0x1d0 drivers/block/nbd.c:251 nbd_put drivers/block/nbd.c:295 [inline] nbd_config_put+0x6dd/0x8c0 drivers/block/nbd.c:1242 nbd_release+0x103/0x190 drivers/block/nbd.c:1507 __blkdev_put+0x548/0x800 fs/block_dev.c:1579 blkdev_put+0x92/0x570 fs/block_dev.c:1632 blkdev_close+0x8c/0xb0 fs/block_dev.c:1640 __fput+0x283/0x920 fs/file_table.c:280 task_work_run+0xdd/0x190 kernel/task_work.c:140 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:174 [inline] exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline] syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The buggy address belongs to the object at ffff888143bf7000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 416 bytes inside of 1024-byte region [ffff888143bf7000, ffff888143bf7400) The buggy address belongs to the page: page:000000005238f4ce refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x143bf0 head:000000005238f4ce order:3 compound_mapcount:0 compound_pincount:0 flags: 0x57ff00000010200(slab\|head) raw: 057ff00000010200 ffffea00004b1400 0000000300000003 ffff888010c41140 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888143bf7080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888143bf7100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888143bf7180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888143bf7200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb Reported-and-tested-by: syzbot+429d3f82d757c211bff3@syzkaller.appspotmail.com Signed-off-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2021-03-07 12:34:06 +01:00
arch	riscv: Get rid of MAX_EARLY_MAPPING_SIZE	2021-03-07 12:34:05 +01:00
block	blk-settings: align max_sectors on "logical_block_size" boundary	2021-03-04 11:38:22 +01:00
certs	certs: Fix blacklist flag type confusion	2021-03-04 11:37:59 +01:00
crypto	crypto: michael_mic - fix broken misalignment handling	2021-03-04 11:38:31 +01:00
Documentation	mm/vmscan: restore zone_reclaim_mode ABI	2021-03-04 11:38:38 +01:00
drivers	nbd: handle device refs for DESTROY_ON_DISCONNECT properly	2021-03-07 12:34:06 +01:00
fs	xfs: Fix assert failure in xfs_setattr_size()	2021-03-07 12:34:05 +01:00
include	net_sched: fix RTNL deadlock again caused by request_module()	2021-03-04 11:38:47 +01:00
init	kgdb: fix to kill breakpoints on initmem after boot	2021-03-04 11:38:46 +01:00
ipc	ipc: adjust proc_ipc_sem_dointvec definition to match prototype	2020-09-05 12:14:29 -07:00
kernel	sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled	2021-03-07 12:34:04 +01:00
lib	udp: fix skb_copy_and_csum_datagram with odd segment sizes	2021-02-17 11:02:28 +01:00
LICENSES	LICENSES/deprecated: add Zlib license text	2020-09-16 14:33:49 +02:00
mm	mm, compaction: make fast_isolate_freepages() stay within zone	2021-03-04 11:38:38 +01:00
net	net: fix up truesize of cloned skb in skb_prepare_for_shift()	2021-03-07 12:34:05 +01:00
samples	watch_queue: Drop references to /dev/watch_queue	2021-03-04 11:37:59 +01:00
scripts	scripts/recordmcount.pl: support big endian for ARCH sh	2021-02-26 10:13:02 +01:00
security	tomoyo: ignore data race while checking quota	2021-03-07 12:34:05 +01:00
sound	ASoC: siu: Fix build error by a wrong const prefix	2021-03-04 11:38:28 +01:00
tools	wireguard: selftests: test multiple parallel streams	2021-03-04 11:38:47 +01:00
usr	Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2020-08-07 13:29:39 -07:00
virt	KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped()	2021-02-26 10:13:01 +01:00
.clang-format	RDMA 5.10 pull request	2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	.gitignore: docs: ignore sphinx_*/ directories	2020-09-10 10:44:31 -06:00
.mailmap	mailmap: add two more addresses of Uwe Kleine-König	2020-12-06 10:19:07 -08:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Jason Cooper to CREDITS	2020-11-30 10:20:34 +01:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2020-12-10 15:30:13 -08:00
Makefile	Linux 5.10.20	2021-03-04 11:38:47 +01:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.