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Robin Murphy 6ef21f34aa arm64: Avoid premature usercopy failure 
commit 295cf15623 upstream.

Al reminds us that the usercopy API must only return complete failure
if absolutely nothing could be copied. Currently, if userspace does
something silly like giving us an unaligned pointer to Device memory,
or a size which overruns MTE tag bounds, we may fail to honour that
requirement when faulting on a multi-byte access even though a smaller
access could have succeeded.

Add a mitigation to the fixup routines to fall back to a single-byte
copy if we faulted on a larger access before anything has been written
to the destination, to guarantee making *some* forward progress. We
needn't be too concerned about the overall performance since this should
only occur when callers are doing something a bit dodgy in the first
place. Particularly broken userspace might still be able to trick
generic_perform_write() into an infinite loop by targeting write() at
an mmap() of some read-only device register where the fault-in load
succeeds but any store synchronously aborts such that copy_to_user() is
genuinely unable to make progress, but, well, don't do that...

CC: stable@vger.kernel.org
Reported-by: Chen Huang <chenhuang5@huawei.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/dc03d5c675731a1f24a62417dba5429ad744234e.1626098433.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2021-07-20 16:00:10 +02:00
arch arm64: Avoid premature usercopy failure 2021-07-20 16:00:10 +02:00
block rq-qos: fix missed wake-ups in rq_qos_throttle try two 2021-07-19 10:04:52 +02:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto crypto: sm2 - fix a memory leak in sm2 2021-07-14 17:06:44 +02:00
Documentation docs: Makefile: Use CONFIG_SHELL not SHELL 2021-07-19 10:04:50 +02:00
drivers EDAC/igen6: fix core dependency AGAIN 2021-07-20 16:00:10 +02:00
fs cifs: Do not use the original cruid when following DFS links for multiuser mounts 2021-07-20 16:00:08 +02:00
include media: subdev: disallow ioctl for saa6588/davinci 2021-07-19 10:04:53 +02:00
init sched/core: Initialize the idle task with preemption disabled 2021-07-14 17:06:21 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel cgroup: verify that source is a string 2021-07-20 16:00:09 +02:00
lib seq_buf: Fix overflow in seq_buf_putmem_hex() 2021-07-19 10:04:52 +02:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/hugetlb: fix refs calculation from unaligned @vaddr 2021-07-20 16:00:10 +02:00
net sctp: add size validation when walking chunks 2021-07-19 10:04:46 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 17:07:08 +02:00
scripts kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' 2021-07-14 17:06:40 +02:00
security smackfs: restrict bytes count in smk_set_cipso() 2021-07-19 10:04:55 +02:00
sound ASoC: tegra: Set driver_name=tegra for all machine drivers 2021-07-19 10:04:51 +02:00
tools KVM: selftests: do not require 64GB in set_memory_region_test 2021-07-20 16:00:08 +02:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio 2021-07-20 16:00:08 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 Marek's other e-mail address and identity without diacritics 2021-06-24 19:40:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -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 Merge branch 'akpm' (patches from Andrew) 2021-06-25 11:05:03 -07:00
Makefile Linux 5.13.3 2021-07-19 10:04:55 +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.