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Amir Goldstein b9cabd2ec2 vfs: fix copy_file_range() regression in cross-fs copies 
commit 868f9f2f8e upstream.

A regression has been reported by Nicolas Boichat, found while using the
copy_file_range syscall to copy a tracefs file.

Before commit 5dae222a5f ("vfs: allow copy_file_range to copy across
devices") the kernel would return -EXDEV to userspace when trying to
copy a file across different filesystems.  After this commit, the
syscall doesn't fail anymore and instead returns zero (zero bytes
copied), as this file's content is generated on-the-fly and thus reports
a size of zero.

Another regression has been reported by He Zhe - the assertion of
WARN_ON_ONCE(ret == -EOPNOTSUPP) can be triggered from userspace when
copying from a sysfs file whose read operation may return -EOPNOTSUPP.

Since we do not have test coverage for copy_file_range() between any two
types of filesystems, the best way to avoid these sort of issues in the
future is for the kernel to be more picky about filesystems that are
allowed to do copy_file_range().

This patch restores some cross-filesystem copy restrictions that existed
prior to commit 5dae222a5f ("vfs: allow copy_file_range to copy across
devices"), namely, cross-sb copy is not allowed for filesystems that do
not implement ->copy_file_range().

Filesystems that do implement ->copy_file_range() have full control of
the result - if this method returns an error, the error is returned to
the user.  Before this change this was only true for fs that did not
implement the ->remap_file_range() operation (i.e.  nfsv3).

Filesystems that do not implement ->copy_file_range() still fall-back to
the generic_copy_file_range() implementation when the copy is within the
same sb.  This helps the kernel can maintain a more consistent story
about which filesystems support copy_file_range().

nfsd and ksmbd servers are modified to fall-back to the
generic_copy_file_range() implementation in case vfs_copy_file_range()
fails with -EOPNOTSUPP or -EXDEV, which preserves behavior of
server-side-copy.

fall-back to generic_copy_file_range() is not implemented for the smb
operation FSCTL_DUPLICATE_EXTENTS_TO_FILE, which is arguably a correct
change of behavior.

Fixes: 5dae222a5f ("vfs: allow copy_file_range to copy across devices")
Link: https://lore.kernel.org/linux-fsdevel/20210212044405.4120619-1-drinkcat@chromium.org/
Link: https://lore.kernel.org/linux-fsdevel/CANMq1KDZuxir2LM5jOTm0xx+BnvW=ZmpsG47CyHFJwnw7zSX6Q@mail.gmail.com/
Link: https://lore.kernel.org/linux-fsdevel/20210126135012.1.If45b7cdc3ff707bc1efa17f5366057d60603c45f@changeid/
Link: https://lore.kernel.org/linux-fsdevel/20210630161320.29006-1-lhenriques@suse.de/
Reported-by: Nicolas Boichat <drinkcat@chromium.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Luis Henriques <lhenriques@suse.de>
Fixes: 64bf5ff58d ("vfs: no fallback for ->copy_file_range")
Link: https://lore.kernel.org/linux-fsdevel/20f17f64-88cb-4e80-07c1-85cb96c83619@windriver.com/
Reported-by: He Zhe <zhe.he@windriver.com>
Tested-by: Namjae Jeon <linkinjeon@kernel.org>
Tested-by: Luis Henriques <lhenriques@suse.de>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2022-07-07 17:54:52 +02:00
Documentation mm/memory-failure: disable unpoison once hw error happens 2022-06-29 09:04:41 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
arch powerpc/bpf: Fix use of user_pt_regs in uapi 2022-07-07 17:54:46 +02:00
block block: pop cached rq before potentially blocking rq_qos_throttle() 2022-06-29 09:04:33 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:28:03 +02:00
crypto crypto: memneq - move into lib/ 2022-06-22 14:28:06 +02:00
drivers hwmon: (occ) Prevent power cap command overwriting poll response 2022-07-07 17:54:51 +02:00
fs vfs: fix copy_file_range() regression in cross-fs copies 2022-07-07 17:54:52 +02:00
include mptcp: fix conflict with <netinet/in.h> 2022-07-07 17:54:51 +02:00
init gcc-12: disable '-Warray-bounds' universally for now 2022-06-22 14:27:55 +02:00
ipc ipc/mqueue: use get_tree_nodev() in mqueue_get_tree() 2022-06-09 10:30:30 +02:00
kernel tick/nohz: unexport __init-annotated tick_nohz_full_setup() 2022-07-02 16:44:55 +02:00
lib crypto: memneq - move into lib/ 2022-06-22 14:28:06 +02:00
mm mm: lru_cache_disable: use synchronize_rcu_expedited 2022-06-29 09:04:41 +02:00
net net: ipv6: unexport __init-annotated seg6_hmac_net_init() 2022-07-07 17:54:51 +02:00
samples samples/landlock: Format with clang-format 2022-06-09 10:30:46 +02:00
scripts modpost: fix section mismatch check for exported init/exit sections 2022-06-29 09:04:43 +02:00
security selinux: free contexts previously transferred in selinux_add_opt() 2022-06-22 14:28:10 +02:00
sound ALSA: hda/realtek: Add quirk for Clevo NS50PU 2022-06-29 09:04:25 +02:00
tools selftests: mptcp: Initialize variables to quiet gcc 12 warnings 2022-07-07 17:54:51 +02:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM: Free new dirty bitmap if creating a new memslot fails 2022-05-20 13:02:05 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.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 hotfixes for 5.18-rc7 2022-05-13 10:22:37 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
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: Add new IOMMU development mailing list 2022-06-29 09:04:27 +02:00
Makefile Linux 5.18.9 2022-07-02 16:44:56 +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.