Linux mainline fork with MSM8998 patches | https://mainline.space | Currently supported devices:
OnePlus 5/5T, Xiaomi Mi 6, F(x)tec Pro¹ (2019 QX1000 model) & Sony Xperia XZ Premium (UNTESTED!)
4058ebf33c
When using a AIO read() operation on the function FS gadget driver a URB is
submitted asynchronously and on URB completion the received data is copied
to the userspace buffer associated with the read operation.
This is done from a kernel worker thread invoking copy_to_user() (through
copy_to_iter()). And while the user space process memory is made available
to the kernel thread using use_mm(), some architecture require in addition
to this that the operation runs with USER_DS set. Otherwise the userspace
memory access will fail.
For example on ARM64 with Privileged Access Never (PAN) and User Access
Override (UAO) enabled the following crash occurs.
Internal error: Accessing user space memory with fs=KERNEL_DS: 9600004f [#1] SMP
Modules linked in:
CPU: 2 PID: 1636 Comm: kworker/2:1 Not tainted 4.9.0-04081-g8ab2dfb-dirty #487
Hardware name: ZynqMP ZCU102 Rev1.0 (DT)
Workqueue: events ffs_user_copy_worker
task: ffffffc87afc8080 task.stack: ffffffc87a00c000
PC is at __arch_copy_to_user+0x190/0x220
LR is at copy_to_iter+0x78/0x3c8
[...]
[<ffffff800847b790>] __arch_copy_to_user+0x190/0x220
[<ffffff80086f25d8>] ffs_user_copy_worker+0x70/0x130
[<ffffff80080b8c64>] process_one_work+0x1dc/0x460
[<ffffff80080b8f38>] worker_thread+0x50/0x4b0
[<ffffff80080bf5a0>] kthread+0xd8/0xf0
[<ffffff8008083680>] ret_from_fork+0x10/0x50
Address this by placing a set_fs(USER_DS) before of the copy operation
and revert it again once the copy operation has finished.
This patch is analogous to commit
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.