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Dae R. Jeong de630248e7 md: fix a warning caused by a race between concurrent md_ioctl()s 
commit c731b84b51 upstream.

Syzkaller reports a warning as belows.
WARNING: CPU: 0 PID: 9647 at drivers/md/md.c:7169
...
Call Trace:
...
RIP: 0010:md_ioctl+0x4017/0x5980 drivers/md/md.c:7169
RSP: 0018:ffff888096027950 EFLAGS: 00010293
RAX: ffff88809322c380 RBX: 0000000000000932 RCX: ffffffff84e266f2
RDX: 0000000000000000 RSI: ffffffff84e299f7 RDI: 0000000000000007
RBP: ffff888096027bc0 R08: ffff88809322c380 R09: ffffed101341a482
R10: ffff888096027940 R11: ffff88809a0d240f R12: 0000000000000932
R13: ffff8880a2c14100 R14: ffff88809a0d2268 R15: ffff88809a0d2408
 __blkdev_driver_ioctl block/ioctl.c:304 [inline]
 blkdev_ioctl+0xece/0x1c10 block/ioctl.c:606
 block_ioctl+0xee/0x130 fs/block_dev.c:1930
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xd5f/0x1380 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

This is caused by a race between two concurrenct md_ioctl()s closing
the array.
CPU1 (md_ioctl())                   CPU2 (md_ioctl())
------                              ------
set_bit(MD_CLOSING, &mddev->flags);
did_set_md_closing = true;
                                    WARN_ON_ONCE(test_bit(MD_CLOSING,
                                            &mddev->flags));
if(did_set_md_closing)
    clear_bit(MD_CLOSING, &mddev->flags);

Fix the warning by returning immediately if the MD_CLOSING bit is set
in &mddev->flags which indicates that the array is being closed.

Fixes: 065e519e71 ("md: MD_CLOSING needs to be cleared after called md_set_readonly or do_md_stop")
Reported-by: syzbot+1e46a0864c1a6e9bd3d8@syzkaller.appspotmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Dae R. Jeong <dae.r.jeong@kaist.ac.kr>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-12-30 11:51:00 +01:00
Documentation KVM: mmu: Fix SPTE encoding of MMIO generation upper half 2020-12-21 13:27:06 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch ARM: dts: exynos: fix USB 3.0 pins supply being turned off on Odroid XU 2020-12-30 11:50:59 +01:00
block blk-mq: In blk_mq_dispatch_rq_list() "no budget" is a reason to kick 2020-12-30 11:50:54 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: af_alg - avoid undefined behavior accessing salg_name 2020-12-30 11:51:00 +01:00
drivers md: fix a warning caused by a race between concurrent md_ioctl()s 2020-12-30 11:51:00 +01:00
fs quota: Sanity-check quota file headers on load 2020-12-30 11:51:00 +01:00
include crypto: af_alg - avoid undefined behavior accessing salg_name 2020-12-30 11:51:00 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel kernel/cpu: add arch override for clear_tasks_mm_cpumask() mm handling 2020-12-30 11:50:56 +01:00
lib lib/syscall: fix syscall registers retrieval on 32-bit platforms 2020-12-11 13:23:32 +01:00
mm mm/zsmalloc.c: drop ZSMALLOC_PGTABLE_MAPPING 2020-12-16 10:56:59 +01:00
net Bluetooth: Fix slab-out-of-bounds read in hci_le_direct_adv_report_evt() 2020-12-30 11:51:00 +01:00
samples samples/bpf: Fix possible deadlock in xdpsock 2020-11-05 11:43:17 +01:00
scripts kbuild: avoid split lines in .mod files 2020-12-30 11:50:57 +01:00
security ima: extend boot_aggregate with kernel measurements 2020-12-08 10:40:24 +01:00
sound ALSA: pcm: oss: Fix potential out-of-bounds shift 2020-12-21 13:27:06 +01:00
tools selftests: fix poll error in udpgro.sh 2020-12-30 11:50:56 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: vgic-v3: Drop the reporting of GICR_TYPER.Last for userspace 2020-12-02 08:49:46 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.85 2020-12-21 13:27:07 +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.