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79ebe9110f
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Sun Ke 79ebe9110f nbd: Fix NULL pointer in flush_workqueue 
Open /dev/nbdX first, the config_refs will be 1 and
the pointers in nbd_device are still null. Disconnect
/dev/nbdX, then reference a null recv_workq. The
protection by config_refs in nbd_genl_disconnect is useless.

[  656.366194] BUG: kernel NULL pointer dereference, address: 0000000000000020
[  656.368943] #PF: supervisor write access in kernel mode
[  656.369844] #PF: error_code(0x0002) - not-present page
[  656.370717] PGD 10cc87067 P4D 10cc87067 PUD 1074b4067 PMD 0
[  656.371693] Oops: 0002 [#1] SMP
[  656.372242] CPU: 5 PID: 7977 Comm: nbd-client Not tainted 5.11.0-rc5-00040-g76c057c84d28 #1
[  656.373661] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[  656.375904] RIP: 0010:mutex_lock+0x29/0x60
[  656.376627] Code: 00 0f 1f 44 00 00 55 48 89 fd 48 83 05 6f d7 fe 08 01 e8 7a c3 ff ff 48 83 05 6a d7 fe 08 01 31 c0 65 48 8b 14 25 00 6d 01 00 <f0> 48 0f b1 55 d
[  656.378934] RSP: 0018:ffffc900005eb9b0 EFLAGS: 00010246
[  656.379350] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[  656.379915] RDX: ffff888104cf2600 RSI: ffffffffaae8f452 RDI: 0000000000000020
[  656.380473] RBP: 0000000000000020 R08: 0000000000000000 R09: ffff88813bd6b318
[  656.381039] R10: 00000000000000c7 R11: fefefefefefefeff R12: ffff888102710b40
[  656.381599] R13: ffffc900005eb9e0 R14: ffffffffb2930680 R15: ffff88810770ef00
[  656.382166] FS:  00007fdf117ebb40(0000) GS:ffff88813bd40000(0000) knlGS:0000000000000000
[  656.382806] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  656.383261] CR2: 0000000000000020 CR3: 0000000100c84000 CR4: 00000000000006e0
[  656.383819] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  656.384370] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  656.384927] Call Trace:
[  656.385111]  flush_workqueue+0x92/0x6c0
[  656.385395]  nbd_disconnect_and_put+0x81/0xd0
[  656.385716]  nbd_genl_disconnect+0x125/0x2a0
[  656.386034]  genl_family_rcv_msg_doit.isra.0+0x102/0x1b0
[  656.386422]  genl_rcv_msg+0xfc/0x2b0
[  656.386685]  ? nbd_ioctl+0x490/0x490
[  656.386954]  ? genl_family_rcv_msg_doit.isra.0+0x1b0/0x1b0
[  656.387354]  netlink_rcv_skb+0x62/0x180
[  656.387638]  genl_rcv+0x34/0x60
[  656.387874]  netlink_unicast+0x26d/0x590
[  656.388162]  netlink_sendmsg+0x398/0x6c0
[  656.388451]  ? netlink_rcv_skb+0x180/0x180
[  656.388750]  ____sys_sendmsg+0x1da/0x320
[  656.389038]  ? ____sys_recvmsg+0x130/0x220
[  656.389334]  ___sys_sendmsg+0x8e/0xf0
[  656.389605]  ? ___sys_recvmsg+0xa2/0xf0
[  656.389889]  ? handle_mm_fault+0x1671/0x21d0
[  656.390201]  __sys_sendmsg+0x6d/0xe0
[  656.390464]  __x64_sys_sendmsg+0x23/0x30
[  656.390751]  do_syscall_64+0x45/0x70
[  656.391017]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

To fix it, just add if (nbd->recv_workq) to nbd_disconnect_and_put().

Fixes: e9e006f5fc ("nbd: fix max number of supported devs")
Signed-off-by: Sun Ke <sunke32@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210512114331.1233964-2-sunke32@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-05-12 08:42:43 -06:00
arch The x86 MM changes in this cycle were: 2021-04-29 11:41:43 -07:00
block block, bfq: avoid circular stable merges 2021-05-12 07:39:23 -06:00
certs certs: add 'x509_revocation_list' to gitignore 2021-04-26 10:48:07 -07:00
crypto for-5.13/drivers-2021-04-27 2021-04-28 14:39:37 -07:00
Documentation - removed get_fs/set_fs 2021-04-29 11:28:08 -07:00
drivers nbd: Fix NULL pointer in flush_workqueue 2021-05-12 08:42:43 -06:00
fs block: reexpand iov_iter after read/write 2021-05-06 09:24:03 -06:00
include blkdev.h: remove unused codes blk_account_rq 2021-05-12 07:40:32 -06:00
init Merge branch 'for-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2021-04-27 18:47:42 -07:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel The x86 MM changes in this cycle were: 2021-04-29 11:41:43 -07:00
lib - removed get_fs/set_fs 2021-04-29 11:28:08 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm \n 2021-04-29 11:06:13 -07:00
net Scheduler updates for this cycle are: 2021-04-28 13:33:57 -07:00
samples vfio/mdev: Correct the function signatures for the mdev_type_attributes 2021-04-12 10:36:00 -06:00
scripts Devicetree updates for v5.13: 2021-04-28 15:50:24 -07:00
security Devicetree updates for v5.13: 2021-04-28 15:50:24 -07:00
sound - Core Frameworks 2021-04-28 15:59:13 -07:00
tools Perf events changes in this cycle were: 2021-04-28 13:03:44 -07:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.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 clang-lto series for v5.12-rc1 2021-02-23 09:28:51 -08:00
.mailmap It's been a relatively busy cycle in docsland, though more than usually 2021-04-26 13:22:43 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Core Frameworks 2021-04-28 15:59:13 -07:00
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 Here's a collection of largely clk driver updates for the merge window. The 2021-04-28 17:13:56 -07:00
Makefile CFI on arm64 series for v5.13-rc1 2021-04-27 10:16:46 -07:00
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.