linux-stable.git/Documentation/filesystems, branch linux-5.4.y

rename(): fix the locking of subdirectories

2024-02-23T07:24:49+00:00

commit 22e111ed6c83dcde3037fc81176012721bc34c0b upstream.

	We should never lock two subdirectories without having taken
->s_vfs_rename_mutex; inode pointer order or not, the "order" proposed
in 28eceeda130f "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: 28eceeda130f "fs: Lock moved directories"
Reviewed-by: Jan Kara 
Signed-off-by: Al Viro 
Signed-off-by: Greg Kroah-Hartman

fs: Lock moved directories

2023-07-27T06:37:26+00:00

commit 28eceeda130f5058074dd007d9c59d2e8bc5af2e upstream.

When a directory is moved to a different directory, some filesystems
(udf, ext4, ocfs2, f2fs, and likely gfs2, reiserfs, and others) need to
update their pointer to the parent and this must not race with other
operations on the directory. Lock the directories when they are moved.
Although not all filesystems need this locking, we perform it in
vfs_rename() because getting the lock ordering right is really difficult
and we don't want to expose these locking details to filesystems.

CC: stable@vger.kernel.org
Signed-off-by: Jan Kara 
Message-Id: <20230601105830.13168-5-jack@suse.cz>
Signed-off-by: Christian Brauner 
Signed-off-by: Greg Kroah-Hartman

docs: Correct missing "d_" prefix for dentry_operations member d_weak_revalidate

2023-03-22T12:28:03+00:00

[ Upstream commit 74596085796fae0cfce3e42ee46bf4f8acbdac55 ]

The details for struct dentry_operations member d_weak_revalidate is
missing a "d_" prefix.

Fixes: af96c1e304f7 ("docs: filesystems: vfs: Convert vfs.txt to RST")
Signed-off-by: Glenn Washburn 
Reviewed-by: Matthew Wilcox (Oracle) 
Link: https://lore.kernel.org/r/20230227184042.2375235-1-development@efficientek.com
Signed-off-by: Jonathan Corbet 
Signed-off-by: Sasha Levin

ext4, doc: fix incorrect h_reserved size

2022-04-27T11:50:50+00:00

commit 7102ffe4c166ca0f5e35137e9f9de83768c2d27d upstream.

According to document and code, ext4_xattr_header's size is 32 bytes, so
h_reserved size should be 3.

Signed-off-by: Wang Jianjian 
Link: https://lore.kernel.org/r/92fcc3a6-7d77-8c09-4126-377fcb4c46a5@huawei.com
Signed-off-by: Theodore Ts'o 
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman

sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs output

2021-03-07T11:20:48+00:00

commit 2efc459d06f1630001e3984854848a5647086232 upstream.

Output defects can exist in sysfs content using sprintf and snprintf.

sprintf does not know the PAGE_SIZE maximum of the temporary buffer
used for outputting sysfs content and it's possible to overrun the
PAGE_SIZE buffer length.

Add a generic sysfs_emit function that knows that the size of the
temporary buffer and ensures that no overrun is done.

Add a generic sysfs_emit_at function that can be used in multiple
call situations that also ensures that no overrun is done.

Validate the output buffer argument to be page aligned.
Validate the offset len argument to be within the PAGE_SIZE buf.

Signed-off-by: Joe Perches 
Link: https://lore.kernel.org/r/884235202216d464d61ee975f7465332c86f76b2.1600285923.git.joe@perches.com
Signed-off-by: Greg Kroah-Hartman

seq_file: document how per-entry resources are managed.

2021-03-04T09:26:48+00:00

commit b3656d8227f4c45812c6b40815d8f4e446ed372a upstream.

Patch series "Fix some seq_file users that were recently broken".

A recent change to seq_file broke some users which were using seq_file
in a non-"standard" way ...  though the "standard" isn't documented, so
they can be excused.  The result is a possible leak - of memory in one
case, of references to a 'transport' in the other.

These three patches:
 1/ document and explain the problem
 2/ fix the problem user in x86
 3/ fix the problem user in net/sctp

This patch (of 3):

Users of seq_file will sometimes find it convenient to take a resource,
such as a lock or memory allocation, in the ->start or ->next operations.
These are per-entry resources, distinct from per-session resources which
are taken in ->start and released in ->stop.

The preferred management of these is release the resource on the
subsequent call to ->next or ->stop.

However prior to Commit 1f4aace60b0e ("fs/seq_file.c: simplify seq_file
iteration code and interface") it happened that ->show would always be
called after ->start or ->next, and a few users chose to release the
resource in ->show.

This is no longer reliable.  Since the mentioned commit, ->next will
always come after a successful ->show (to ensure m->index is updated
correctly), so the original ordering cannot be maintained.

This patch updates the documentation to clearly state the required
behaviour.  Other patches will fix the few problematic users.

[akpm@linux-foundation.org: fix typo, per Willy]

Link: https://lkml.kernel.org/r/161248518659.21478.2484341937387294998.stgit@noble1
Link: https://lkml.kernel.org/r/161248539020.21478.3147971477400875336.stgit@noble1
Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
Signed-off-by: NeilBrown 
Cc: Xin Long 
Cc: Alexander Viro 
Cc: Jonathan Corbet 
Cc: Ingo Molnar 
Cc: Dave Hansen 
Cc: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: Vlad Yasevich 
Cc: Neil Horman 
Cc: Marcelo Ricardo Leitner 
Cc: "David S. Miller" 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

affs: fix basic permission bits to actually work

2020-09-09T17:12:34+00:00

commit d3a84a8d0dde4e26bc084b36ffcbdc5932ac85e2 upstream.

The basic permission bits (protection bits in AmigaOS) have been broken
in Linux' AFFS - it would only set bits, but never delete them.
Also, contrary to the documentation, the Archived bit was not handled.

Let's fix this for good, and set the bits such that Linux and classic
AmigaOS can coexist in the most peaceful manner.

Also, update the documentation to represent the current state of things.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Max Staudt 
Signed-off-by: David Sterba 
Signed-off-by: Greg Kroah-Hartman

cifs_atomic_open(): fix double-put on late allocation failure

2020-03-18T06:17:51+00:00

commit d9a9f4849fe0c9d560851ab22a85a666cddfdd24 upstream.

several iterations of ->atomic_open() calling conventions ago, we
used to need fput() if ->atomic_open() failed at some point after
successful finish_open().  Now (since 2016) it's not needed -
struct file carries enough state to make fput() work regardless
of the point in struct file lifecycle and discarding it on
failure exits in open() got unified.  Unfortunately, I'd missed
the fact that we had an instance of ->atomic_open() (cifs one)
that used to need that fput(), as well as the stale comment in
finish_open() demanding such late failure handling.  Trivially
fixed...

Fixes: fe9ec8291fca "do_last(): take fput() on error after opening to out:"
Cc: stable@kernel.org # v4.7+
Signed-off-by: Al Viro 
Signed-off-by: Greg Kroah-Hartman

Merge tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

2019-09-27T22:54:24+00:00

Pull fuse virtio-fs support from Miklos Szeredi:
 "Virtio-fs allows exporting directory trees on the host and mounting
  them in guest(s).

  This isn't actually a new filesystem, but a glue layer between the
  fuse filesystem and a virtio based back-end.

  It's similar in functionality to the existing virtio-9p solution, but
  significantly faster in benchmarks and has better POSIX compliance.
  Further permformance improvements can be achieved by sharing the page
  cache between host and guest, allowing for faster I/O and reduced
  memory use.

  Kata Containers have been including the out-of-tree virtio-fs (with
  the shared page cache patches as well) since version 1.7 as an
  experimental feature. They have been active in development and plan to
  switch from virtio-9p to virtio-fs as their default solution. There
  has been interest from other sources as well.

  The userspace infrastructure is slated to be merged into qemu once the
  kernel part hits mainline.

  This was developed by Vivek Goyal, Dave Gilbert and Stefan Hajnoczi"

* tag 'virtio-fs-5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  virtio-fs: add virtiofs filesystem
  virtio-fs: add Documentation/filesystems/virtiofs.rst
  fuse: reserve values for mapping protocol

Merge tag 'ceph-for-5.4-rc1' of git://github.com/ceph/ceph-client

2019-09-25T17:21:13+00:00

Pull ceph updates from Ilya Dryomov:
 "The highlights are:

   - automatic recovery of a blacklisted filesystem session (Zheng Yan).
     This is disabled by default and can be enabled by mounting with the
     new "recover_session=clean" option.

   - serialize buffered reads and O_DIRECT writes (Jeff Layton). Care is
     taken to avoid serializing O_DIRECT reads and writes with each
     other, this is based on the exclusion scheme from NFS.

   - handle large osdmaps better in the face of fragmented memory
     (myself)

   - don't limit what security.* xattrs can be get or set (Jeff Layton).
     We were overly restrictive here, unnecessarily preventing things
     like file capability sets stored in security.capability from
     working.

   - allow copy_file_range() within the same inode and across different
     filesystems within the same cluster (Luis Henriques)"

* tag 'ceph-for-5.4-rc1' of git://github.com/ceph/ceph-client: (41 commits)
  ceph: call ceph_mdsc_destroy from destroy_fs_client
  libceph: use ceph_kvmalloc() for osdmap arrays
  libceph: avoid a __vmalloc() deadlock in ceph_kvmalloc()
  ceph: allow object copies across different filesystems in the same cluster
  ceph: include ceph_debug.h in cache.c
  ceph: move static keyword to the front of declarations
  rbd: pull rbd_img_request_create() dout out into the callers
  ceph: reconnect connection if session hang in opening state
  libceph: drop unused con parameter of calc_target()
  ceph: use release_pages() directly
  rbd: fix response length parameter for encoded strings
  ceph: allow arbitrary security.* xattrs
  ceph: only set CEPH_I_SEC_INITED if we got a MAC label
  ceph: turn ceph_security_invalidate_secctx into static inline
  ceph: add buffered/direct exclusionary locking for reads and writes
  libceph: handle OSD op ceph_pagelist_append() errors
  ceph: don't return a value from void function
  ceph: don't freeze during write page faults
  ceph: update the mtime when truncating up
  ceph: fix indentation in __get_snap_name()
  ...