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Al Viro 22e111ed6c rename(): fix the locking of subdirectories 
We should never lock two subdirectories without having taken
->s_vfs_rename_mutex; inode pointer order or not, the "order" proposed
in 28eceeda13 "fs: Lock moved directories" is not transitive, with
the usual consequences.

	The rationale for locking renamed subdirectory in all cases was
the possibility of race between rename modifying .. in a subdirectory to
reflect the new parent and another thread modifying the same subdirectory.
For a lot of filesystems that's not a problem, but for some it can lead
to trouble (e.g. the case when short directory contents is kept in the
inode, but creating a file in it might push it across the size limit
and copy its contents into separate data block(s)).

	However, we need that only in case when the parent does change -
otherwise ->rename() doesn't need to do anything with .. entry in the
first place.  Some instances are lazy and do a tautological update anyway,
but it's really not hard to avoid.

Amended locking rules for rename():
	find the parent(s) of source and target
	if source and target have the same parent
		lock the common parent
	else
		lock ->s_vfs_rename_mutex
		lock both parents, in ancestor-first order; if neither
		is an ancestor of another, lock the parent of source
		first.
	find the source and target.
	if source and target have the same parent
		if operation is an overwriting rename of a subdirectory
			lock the target subdirectory
	else
		if source is a subdirectory
			lock the source
		if target is a subdirectory
			lock the target
	lock non-directories involved, in inode pointer order if both
	source and target are such.

That way we are guaranteed that parents are locked (for obvious reasons),
that any renamed non-directory is locked (nfsd relies upon that),
that any victim is locked (emptiness check needs that, among other things)
and subdirectory that changes parent is locked (needed to protect the update
of .. entries).  We are also guaranteed that any operation locking more
than one directory either takes ->s_vfs_rename_mutex or locks a parent
followed by its child.

Cc: stable@vger.kernel.org
Fixes: 28eceeda13 "fs: Lock moved directories"
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2023-11-25 02:53:20 -05:00
arch parisc architecture fixes for kernel v6.7-rc1 (part 2): 2023-11-12 11:05:31 -08:00
block blk-core: use pr_warn_ratelimited() in bio_check_ro() 2023-11-07 08:15:23 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression in ahash and hides the Kconfig sub-options for the jitter RNG. 2023-11-09 17:04:58 -08:00
Documentation rename(): fix the locking of subdirectories 2023-11-25 02:53:20 -05:00
drivers wifi: iwlwifi: fix system commands group ordering 2023-11-12 11:34:19 -08:00
fs rename(): fix the locking of subdirectories 2023-11-25 02:53:20 -05:00
include Probes fixes for v6.7-rc1: 2023-11-10 16:35:04 -08:00
init As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
io_uring io_uring: do not clamp read length for multishot read 2023-11-06 13:41:58 -07:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel Probes fixes for v6.7-rc1: 2023-11-10 16:35:04 -08:00
lib lib: test_objpool: make global variables static 2023-11-10 19:59:04 +09:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: report failures when memblock_can_resize is not set 2023-11-08 09:40:13 -08:00
net Including fixes from netfilter and bpf. 2023-11-09 17:09:35 -08:00
rust Kbuild updates for v6.7 2023-11-04 08:07:19 -10:00
samples Landlock updates for v6.7-rc1 2023-11-03 09:28:53 -10:00
scripts Kbuild updates for v6.7 2023-11-04 08:07:19 -10:00
security selinux: saner handling of policy reloads 2023-11-16 12:45:33 -05:00
sound sound fixes for 6.7-rc1 2023-11-10 11:57:51 -08:00
tools LoongArch changes for v6.7 2023-11-12 10:58:08 -08:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap As usual, lots of singleton and doubleton patches all over the tree and 2023-11-02 20:53:31 -10:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig
MAINTAINERS - removed AR7 platform support 2023-11-10 09:19:46 -08:00
Makefile Linux 6.7-rc1 2023-11-12 16:19:07 -08:00
README

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.