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Wesley Cheng 24729b307e usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete 
FFS based applications can utilize the aio_cancel() callback to dequeue
pending USB requests submitted to the UDC.  There is a scenario where the
FFS application issues an AIO cancel call, while the UDC is handling a
soft disconnect.  For a DWC3 based implementation, the callstack looks
like the following:

    DWC3 Gadget                               FFS Application
dwc3_gadget_soft_disconnect()              ...
  --> dwc3_stop_active_transfers()
    --> dwc3_gadget_giveback(-ESHUTDOWN)
      --> ffs_epfile_async_io_complete()   ffs_aio_cancel()
        --> usb_ep_free_request()            --> usb_ep_dequeue()

There is currently no locking implemented between the AIO completion
handler and AIO cancel, so the issue occurs if the completion routine is
running in parallel to an AIO cancel call coming from the FFS application.
As the completion call frees the USB request (io_data->req) the FFS
application is also referencing it for the usb_ep_dequeue() call.  This can
lead to accessing a stale/hanging pointer.

commit b566d38857 ("usb: gadget: f_fs: use io_data->status consistently")
relocated the usb_ep_free_request() into ffs_epfile_async_io_complete().
However, in order to properly implement locking to mitigate this issue, the
spinlock can't be added to ffs_epfile_async_io_complete(), as
usb_ep_dequeue() (if successfully dequeuing a USB request) will call the
function driver's completion handler in the same context.  Hence, leading
into a deadlock.

Fix this issue by moving the usb_ep_free_request() back to
ffs_user_copy_worker(), and ensuring that it explicitly sets io_data->req
to NULL after freeing it within the ffs->eps_lock.  This resolves the race
condition above, as the ffs_aio_cancel() routine will not continue
attempting to dequeue a request that has already been freed, or the
ffs_user_copy_work() not freeing the USB request until the AIO cancel is
done referencing it.

This fix depends on
  commit b566d38857 ("usb: gadget: f_fs: use io_data->status
  consistently")

Fixes: 2e4c7553cd ("usb: gadget: f_fs: add aio support")
Cc: stable <stable@kernel.org>	# b566d38857 ("usb: gadget: f_fs: use io_data->status consistently")
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
Link: https://lore.kernel.org/r/20240409014059.6740-1-quic_wcheng@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2024-04-23 16:10:55 -07:00
Documentation Kernfs bugfix and documentation update for 6.9-rc5 2024-04-21 10:30:21 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch - Add a missing memory barrier in the concurrency ID mm switching 2024-04-21 09:39:36 -07:00
block block-6.9-20240420 2024-04-20 11:28:02 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
drivers usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete 2024-04-23 16:10:55 -07:00
fs Kernfs bugfix and documentation update for 6.9-rc5 2024-04-21 10:30:21 -07:00
include Char/Misc driver fixes for 6.9-rc5 2024-04-21 10:32:58 -07:00
init init/main.c: Fix potential static_command_line memory overflow 2024-04-13 00:59:36 +09:00
io_uring io_uring/net: restore msg_control on sendzc retry 2024-04-08 21:48:41 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel - Add a missing memory barrier in the concurrency ID mm switching 2024-04-21 09:39:36 -07:00
lib hardening fixes for v6.9-rc5 2024-04-19 14:10:11 -07:00
mm mm/shmem: inline shmem_is_huge() for disabled transparent hugepages 2024-04-16 15:39:51 -07:00
net netfilter pull request 24-04-18 2024-04-18 13:12:37 +02:00
rust Kbuild updates for v6.9 2024-03-21 14:41:00 -07:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts hardening fixes for v6.9-rc4 2024-04-10 13:31:34 -07:00
security security: Place security_path_post_mknod() where the original IMA call was 2024-04-03 10:21:32 -07:00
sound ALSA: seq: ump: Fix conversion from MIDI2 to MIDI1 UMP messages 2024-04-19 12:07:14 +02:00
tools * Clean up SVM's enter/exit assembly code so that it can be compiled 2024-04-20 11:10:51 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start() 2024-04-11 12:58:53 -07:00
.clang-format clang-format: Update with v6.7-rc4's `for_each` macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
…
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap TTY/Serial driver fixes for 6.9-rc5 2024-04-21 10:27:01 -07:00
.rustfmt.toml
…
COPYING
…
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
…
MAINTAINERS TTY/Serial driver fixes for 6.9-rc5 2024-04-21 10:27:01 -07:00
Makefile Linux 6.9-rc5 2024-04-21 12:35:54 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.