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Tetsuo Handa ee41198757 block/loop: fix deadlock after loop_set_status commit `1e047eaab3` upstream. syzbot is reporting deadlocks at __blkdev_get() [1]. ---------------------------------------- [ 92.493919] systemd-udevd D12696 525 1 0x00000000 [ 92.495891] Call Trace: [ 92.501560] schedule+0x23/0x80 [ 92.502923] schedule_preempt_disabled+0x5/0x10 [ 92.504645] __mutex_lock+0x416/0x9e0 [ 92.510760] __blkdev_get+0x73/0x4f0 [ 92.512220] blkdev_get+0x12e/0x390 [ 92.518151] do_dentry_open+0x1c3/0x2f0 [ 92.519815] path_openat+0x5d9/0xdc0 [ 92.521437] do_filp_open+0x7d/0xf0 [ 92.527365] do_sys_open+0x1b8/0x250 [ 92.528831] do_syscall_64+0x6e/0x270 [ 92.530341] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 92.931922] 1 lock held by systemd-udevd/525: [ 92.933642] #0: 00000000a2849e25 (&bdev->bd_mutex){+.+.}, at: __blkdev_get+0x73/0x4f0 ---------------------------------------- The reason of deadlock turned out that wait_event_interruptible() in blk_queue_enter() got stuck with bdev->bd_mutex held at __blkdev_put() due to q->mq_freeze_depth == 1. ---------------------------------------- [ 92.787172] a.out S12584 634 633 0x80000002 [ 92.789120] Call Trace: [ 92.796693] schedule+0x23/0x80 [ 92.797994] blk_queue_enter+0x3cb/0x540 [ 92.803272] generic_make_request+0xf0/0x3d0 [ 92.807970] submit_bio+0x67/0x130 [ 92.810928] submit_bh_wbc+0x15e/0x190 [ 92.812461] __block_write_full_page+0x218/0x460 [ 92.815792] __writepage+0x11/0x50 [ 92.817209] write_cache_pages+0x1ae/0x3d0 [ 92.825585] generic_writepages+0x5a/0x90 [ 92.831865] do_writepages+0x43/0xd0 [ 92.836972] __filemap_fdatawrite_range+0xc1/0x100 [ 92.838788] filemap_write_and_wait+0x24/0x70 [ 92.840491] __blkdev_put+0x69/0x1e0 [ 92.841949] blkdev_close+0x16/0x20 [ 92.843418] __fput+0xda/0x1f0 [ 92.844740] task_work_run+0x87/0xb0 [ 92.846215] do_exit+0x2f5/0xba0 [ 92.850528] do_group_exit+0x34/0xb0 [ 92.852018] SyS_exit_group+0xb/0x10 [ 92.853449] do_syscall_64+0x6e/0x270 [ 92.854944] entry_SYSCALL_64_after_hwframe+0x42/0xb7 [ 92.943530] 1 lock held by a.out/634: [ 92.945105] #0: 00000000a2849e25 (&bdev->bd_mutex){+.+.}, at: __blkdev_put+0x3c/0x1e0 ---------------------------------------- The reason of q->mq_freeze_depth == 1 turned out that loop_set_status() forgot to call blk_mq_unfreeze_queue() at error paths for info->lo_encrypt_type != NULL case. ---------------------------------------- [ 37.509497] CPU: 2 PID: 634 Comm: a.out Tainted: G W 4.16.0+ #457 [ 37.513608] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017 [ 37.518832] RIP: 0010:blk_freeze_queue_start+0x17/0x40 [ 37.521778] RSP: 0018:ffffb0c2013e7c60 EFLAGS: 00010246 [ 37.524078] RAX: 0000000000000000 RBX: ffff8b07b1519798 RCX: 0000000000000000 [ 37.527015] RDX: 0000000000000002 RSI: ffffb0c2013e7cc0 RDI: ffff8b07b1519798 [ 37.529934] RBP: ffffb0c2013e7cc0 R08: 0000000000000008 R09: 47a189966239b898 [ 37.532684] R10: dad78b99b278552f R11: 9332dca72259d5ef R12: ffff8b07acd73678 [ 37.535452] R13: 0000000000004c04 R14: 0000000000000000 R15: ffff8b07b841e940 [ 37.538186] FS: 00007fede33b9740(0000) GS:ffff8b07b8e80000(0000) knlGS:0000000000000000 [ 37.541168] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 37.543590] CR2: 00000000206fdf18 CR3: 0000000130b30006 CR4: 00000000000606e0 [ 37.546410] Call Trace: [ 37.547902] blk_freeze_queue+0x9/0x30 [ 37.549968] loop_set_status+0x67/0x3c0 [loop] [ 37.549975] loop_set_status64+0x3b/0x70 [loop] [ 37.549986] lo_ioctl+0x223/0x810 [loop] [ 37.549995] blkdev_ioctl+0x572/0x980 [ 37.550003] block_ioctl+0x34/0x40 [ 37.550006] do_vfs_ioctl+0xa7/0x6d0 [ 37.550017] ksys_ioctl+0x6b/0x80 [ 37.573076] SyS_ioctl+0x5/0x10 [ 37.574831] do_syscall_64+0x6e/0x270 [ 37.576769] entry_SYSCALL_64_after_hwframe+0x42/0xb7 ---------------------------------------- [1] https://syzkaller.appspot.com/bug?id=cd662bc3f6022c0979d01a262c318fab2ee9b56f Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Reported-by: syzbot <bot+48594378e9851eab70bcd6f99327c7db58c5a28a@syzkaller.appspotmail.com> Fixes: `ecdd09597a` ("block/loop: fix race between I/O and set_status") Cc: Ming Lei <tom.leiming@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: stable <stable@vger.kernel.org> Cc: Jens Axboe <axboe@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		History 2018-04-19 08:54:10 +02:00
arch	zboot: fix stack protector in compressed boot phase	2018-04-19 08:54:08 +02:00
block	blk-mq: don't keep offline CPUs mapped to hctx 0	2018-04-19 08:54:09 +02:00
certs	certs/blacklist_nohashes.c: fix const confusion in certs blacklist	2018-02-21 15:35:43 -08:00
crypto	crypto: ahash - Fix early termination in hash walk	2018-04-08 14:29:50 +02:00
Documentation	serial: 8250: Add Nuvoton NPCM UART	2018-04-08 14:29:49 +02:00
drivers	block/loop: fix deadlock after loop_set_status	2018-04-19 08:54:10 +02:00
firmware	kbuild: remove all dummy assignments to obj-	2017-11-18 11:46:06 +09:00
fs	nfsd: fix incorrect umasks	2018-04-19 08:54:10 +02:00
include	media: v4l2-core: fix size of devnode_nums[] bitarray	2018-04-19 08:54:05 +02:00
init	jump_label: Disable jump labels in __exit code	2018-03-20 08:57:17 +01:00
ipc	ipc/shm.c: add split function to shm_vm_ops	2018-03-28 13:42:05 -10:00
kernel	perf/core: Fix use-after-free in uprobe_perf_close()	2018-04-19 08:54:07 +02:00
lib	lib: fix stall in __bitmap_parselist()	2018-04-19 08:54:08 +02:00
LICENSES	LICENSES: Add MPL-1.1 license	2018-01-06 10:59:44 -07:00
mm	mm/kmemleak.c: wait for scan completion before disabling free	2018-03-28 13:42:05 -10:00
net	sunrpc: remove incorrect HMAC request initialization	2018-04-19 08:54:08 +02:00
samples	- do not build samples when cross compiling (Michal Hocko)	2018-02-27 10:39:29 -08:00
scripts	kbuild: rpm-pkg: Support GNU tar >= 1.29	2018-03-28 01:42:17 +09:00
security	apparmor: fix resource audit messages when auditing peer	2018-04-19 08:54:10 +02:00
sound	ALSA: pcm: potential uninitialized return values	2018-03-27 15:20:19 +02:00
tools	perf intel-pt: Fix timestamp following overflow	2018-04-19 08:54:07 +02:00
usr	initramfs: fix initramfs rebuilds w/ compression after disabling	2017-11-03 07:39:19 -07:00
virt	kvm/arm fixes for 4.16, take 2	2018-03-15 21:45:37 +01:00
.cocciconfig	scripts: add Linux .cocciconfig for coccinelle	2016-07-22 12:13:39 +02:00
.get_maintainer.ignore	Add hch to .get_maintainer.ignore	2015-08-21 14:30:10 -07:00
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	.gitignore: ignore ASN.1 auto generated files	2018-02-14 21:05:38 +01:00
.mailmap	mailmap: Update email address for Gregory CLEMENT	2018-03-09 17:48:50 +01:00
COPYING	[PATCH] update FSF address in COPYING	2005-09-10 10:06:29 -07:00
CREDITS	MAINTAINERS: update TPM driver infrastructure changes	2017-11-09 17:58:40 -08:00
Kbuild	Kbuild updates for v4.15	2017-11-17 17:45:29 -08:00
Kconfig	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
MAINTAINERS	Merge branch 'akpm' (patches from Andrew)	2018-03-28 14:34:55 -10:00
Makefile	Linux 4.16.2	2018-04-12 12:30:01 +02:00
README	README: add a new README file, pointing to the Documentation/	2016-10-24 08:12:35 -02:00

README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.