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Udipto Goswami dca51010f7 usb: gadget: configfs: Restrict symlink creation is UDC already binded 
[ Upstream commit 89e7252d6c ]

During enumeration or composition switch,a userspace process
agnostic of the conventions of configs can try to create function
symlinks even after the UDC is bound to current config which is
not correct. Potentially it can create duplicates within the
current config.

Prevent this by adding a check if udc_name already exists, then bail
out of cfg_link.

Following is an example:

Step1:
ln -s X1 ffs.a
-->cfg_link
--> usb_get_function(ffs.a)
	->ffs_alloc

	CFG->FUNC_LIST: <ffs.a>
	C->FUNCTION: <empty>

Step2:
echo udc.name > /config/usb_gadget/g1/UDC
--> UDC_store
	->composite_bind
	->usb_add_function

	CFG->FUNC_LIST: <empty>
	C->FUNCTION: <ffs.a>

Step3:
ln -s Y1 ffs.a
-->cfg_link
-->usb_get_function(ffs.a)
	->ffs_alloc

	CFG->FUNC_LIST: <ffs.a>
	C->FUNCTION: <ffs.a>

both the lists corresponds to the same function instance ffs.a
but the usb_function* pointer is different because in step 3
ffs_alloc has created a new reference to usb_function* for
ffs.a and added it to cfg_list.

Step4:
Now a composition switch involving <ffs.b,ffs.a> is executed.

the composition switch will involve 3 things:
	1. unlinking the previous functions existing
	2. creating new symlinks
	3. writing UDC

However, the composition switch is generally taken care by
userspace process which creates the symlinks in its own
nomenclature(X*) and removes only those.
So it won't be able to remove Y1 which user had created
by own.

Due to this the new symlinks cannot be created for ffs.a
since the entry already exists in CFG->FUNC_LIST.

The state of the CFG->FUNC_LIST is as follows:
	CFG->FUNC_LIST: <ffs.a>

Fixes: 88af8bbe4e ("usb: gadget: the start of the configfs interface")
Signed-off-by: Krishna Kurapati PSSNV <quic_kriskura@quicinc.com>
Signed-off-by: Udipto Goswami <quic_ugoswami@quicinc.com>
Link: https://lore.kernel.org/r/20230201132308.31523-1-quic_ugoswami@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2023-03-10 09:33:35 +01:00
arch alpha/boot/tools/objstrip: fix the check for ELF header 2023-03-10 09:33:30 +01:00
block block: use proper return value from bio_failfast() 2023-03-10 09:32:47 +01:00
certs certs: Fix build error when PKCS#11 URI contains semicolon 2023-02-09 11:28:11 +01:00
crypto crypto: rsa-pkcs1pad - Use akcipher_request_complete 2023-03-10 09:33:03 +01:00
Documentation ASoC: dt-bindings: meson: fix gx-card codec node regex 2023-03-10 09:33:19 +01:00
drivers usb: gadget: configfs: Restrict symlink creation is UDC already binded 2023-03-10 09:33:35 +01:00
fs gfs2: jdata writepage fix 2023-03-10 09:33:25 +01:00
include drivers: base: transport_class: fix possible memory leak 2023-03-10 09:33:34 +01:00
init gcc: disable -Warray-bounds for gcc-11 too 2023-01-14 10:33:43 +01:00
io_uring use less confusing names for iov_iter direction initializers 2023-02-09 11:28:04 +01:00
ipc ipc: fix memory leak in init_mqueue_fs() 2022-12-31 13:32:01 +01:00
kernel bpf: Fix global subprog context argument resolution logic 2023-03-10 09:33:06 +01:00
lib kobject: Fix slab-out-of-bounds in fill_kobj_path() 2023-03-10 09:33:30 +01:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/gup: add folio to list when folio_isolate_lru() succeed 2023-02-22 12:59:54 +01:00
net NFS: fix disabling of swap 2023-03-10 09:33:22 +01:00
rust rust: print: avoid evaluating arguments in pr_* macros in unsafe blocks 2023-02-06 08:06:34 +01:00
samples ftrace: Export ftrace_free_filter() to modules 2023-02-01 08:34:37 +01:00
scripts scripts/tags.sh: fix incompatibility with PCRE2 2023-03-03 11:52:25 +01:00
security randstruct: disable Clang 15 support 2023-02-25 11:25:43 +01:00
sound ALSA: hda/hdmi: Register with vga_switcheroo on Dual GPU Macbooks 2023-03-10 09:33:23 +01:00
tools objtool: add UACCESS exceptions for __tsan_volatile_read/write 2023-03-10 09:33:28 +01:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt kvm/vfio: Fix potential deadlock on vfio group_lock 2023-02-01 08:34:36 +01:00
.clang-format inet: ping: use hlist_nulls rcu iterator during lookup 2022-12-01 12:42:46 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore Kbuild: add Rust support 2022-09-28 09:02:20 +02:00
.mailmap 9 hotfixes. 6 for MM, 3 for other areas. Four of these patches address 2022-12-10 17:10:52 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove Michal Marek from Kbuild maintainers 2022-11-16 14:53:00 +09:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS audit: update the mailing list in MAINTAINERS 2023-02-25 11:25:42 +01:00
Makefile Linux 6.1.15 2023-03-03 11:52:25 +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.