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Baokun Li 1a3f1cf870 ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl commit `3cbf0e392f` upstream. Hulk Robot reported a KASAN report about use-after-free: ================================================================== BUG: KASAN: use-after-free in __list_del_entry_valid+0x13d/0x160 Read of size 8 at addr ffff888035e37d98 by task ubiattach/1385 [...] Call Trace: klist_dec_and_del+0xa7/0x4a0 klist_put+0xc7/0x1a0 device_del+0x4d4/0xed0 cdev_device_del+0x1a/0x80 ubi_attach_mtd_dev+0x2951/0x34b0 [ubi] ctrl_cdev_ioctl+0x286/0x2f0 [ubi] Allocated by task 1414: device_add+0x60a/0x18b0 cdev_device_add+0x103/0x170 ubi_create_volume+0x1118/0x1a10 [ubi] ubi_cdev_ioctl+0xb7f/0x1ba0 [ubi] Freed by task 1385: cdev_device_del+0x1a/0x80 ubi_remove_volume+0x438/0x6c0 [ubi] ubi_cdev_ioctl+0xbf4/0x1ba0 [ubi] [...] ================================================================== The lock held by ctrl_cdev_ioctl is ubi_devices_mutex, but the lock held by ubi_cdev_ioctl is ubi->device_mutex. Therefore, the two locks can be concurrent. ctrl_cdev_ioctl contains two operations: ubi_attach and ubi_detach. ubi_detach is bug-free because it uses reference counting to prevent concurrency. However, uif_init and uif_close in ubi_attach may race with ubi_cdev_ioctl. uif_init will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 _______________________\|________________________\|______________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_add_volume // sysfs exist kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume cdev_del // double free cdev_device_del And uif_close will race with ubi_cdev_ioctl as in the following stack. cpu1 cpu2 cpu3 _______________________\|________________________\|______________________ ctrl_cdev_ioctl ubi_attach_mtd_dev uif_init ubi_cdev_ioctl ubi_create_volume cdev_device_add ubi_debugfs_init_dev //error goto out_uif; uif_close kill_volumes ubi_cdev_ioctl ubi_remove_volume cdev_device_del // first free ubi_free_volume // double free The cause of this problem is that commit `714fb87e8b` make device "available" before it becomes accessible via sysfs. Therefore, we roll back the modification. We will fix the race condition between ubi device creation and udev by removing ubi_get_device in vol_attribute_show and dev_attribute_show.This avoids accessing uninitialized ubi_devices[ubi_num]. ubi_get_device is used to prevent devices from being deleted during sysfs execution. However, now kernfs ensures that devices will not be deleted before all reference counting are released. The key process is shown in the following stack. device_del device_remove_attrs device_remove_groups sysfs_remove_groups sysfs_remove_group remove_files kernfs_remove_by_name kernfs_remove_by_name_ns __kernfs_remove kernfs_drain Fixes: `714fb87e8b` ("ubi: Fix race condition between ubi device creation and udev") Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Baokun Li <libaokun1@huawei.com> Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-04-08 14:24:11 +02:00
arch	crypto: arm/aes-neonbs-cbc - Select generic cbc and aes	2022-04-08 14:24:10 +02:00
block	Revert "Revert "block, bfq: honor already-setup queue merges""	2022-04-08 14:23:56 +02:00
certs	certs: Add support for using elliptic curve keys for signing modules	2021-08-23 19:55:42 +03:00
crypto	crypto: xts - Add softdep on ecb	2022-04-08 14:23:55 +02:00
Documentation	ALSA: hda/realtek: Add alc256-samsung-headphone fixup	2022-04-08 14:24:03 +02:00
drivers	ubi: Fix race condition between ctrl_cdev_ioctl and ubi_cdev_ioctl	2022-04-08 14:24:11 +02:00
fs	gfs2: Make sure FITRIM minlen is rounded up to fs block size	2022-04-08 14:24:10 +02:00
include	rxrpc: Fix call timer start racing with call destruction	2022-04-08 14:24:10 +02:00
init	init: make unknown command line param message clearer	2021-11-18 19:17:11 +01:00
ipc	ipc/sem: do not sleep with a spin lock held	2022-02-08 18:34:03 +01:00
kernel	watch_queue: Free the page array when watch_queue is dismantled	2022-04-08 14:24:11 +02:00
lib	XArray: Update the LRU list in xas_split()	2022-04-08 14:24:09 +02:00
LICENSES	LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"	2021-07-15 06:31:24 -06:00
mm	mm/kmemleak: reset tag when compare object pointer	2022-04-08 14:22:56 +02:00
net	rxrpc: Fix call timer start racing with call destruction	2022-04-08 14:24:10 +02:00
samples	samples/bpf, xdpsock: Fix race when running for fix duration of time	2022-04-08 14:23:40 +02:00
scripts	modpost: restore the warning message for missing symbol versions	2022-04-08 14:24:10 +02:00
security	Fix incorrect type in assignment of ipv6 port for audit	2022-04-08 14:23:55 +02:00
sound	ASoC: mediatek: mt6358: add missing EXPORT_SYMBOLs	2022-04-08 14:24:11 +02:00
tools	selftests: test_vxlan_under_vrf: Fix broken test case	2022-04-08 14:23:52 +02:00
usr	usr/include/Makefile: add linux/nfc.h to the compile-test coverage	2022-02-01 17:27:15 +01:00
virt	KVM: Prevent module exit until all VMs are freed	2022-04-08 14:24:07 +02:00
.clang-format	clang-format: Update with the latest for_each macro list	2021-05-12 23:32:39 +02:00
.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: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: add Andrej Shadura	2021-10-18 20:22:03 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Daniel Drake to credits	2021-09-21 08:34:58 +03:00
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	MAINTAINERS: adjust file entry for of_net.c after movement	2022-03-08 19:12:53 +01:00
Makefile	Linux 5.15.32	2022-03-28 09:58:46 +02:00
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.