Permission to create an object (create, mkdir, symlink, mknod) needs to
take supplementary groups into account.
Add a supplementary group request extension. This can contain an arbitrary
number of group IDs and can be added to any request. This extension is not
added to any request by default.
Add FUSE_CREATE_SUPP_GROUP init flag to enable supplementary group info in
creation requests. This adds just a single supplementary group that
matches the parent group in the case described above. In other cases the
extension is not added.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Will need to add supplementary groups to create messages, so add the
general concept of a request extension. A request extension is appended to
the end of the main request. It has a header indicating the size and type
of the extension.
The create security context (fuse_secctx_*) is similar to the generic
request extension, so include that as well in a backward compatible manner.
Add the total extension length to the request header. The offset of the
extension block within the request can be calculated by:
inh->len - inh->total_extlen * 8
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
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Merge tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse
Pull fuse update from Miklos Szeredi:
- Allow some write requests to proceed in parallel
- Fix a performance problem with allow_sys_admin_access
- Add a special kind of invalidation that doesn't immediately purge
submounts
- On revalidation treat the target of rename(RENAME_NOREPLACE) the same
as open(O_EXCL)
- Use type safe helpers for some mnt_userns transformations
* tag 'fuse-update-6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
fuse: Rearrange fuse_allow_current_process checks
fuse: allow non-extending parallel direct writes on the same file
fuse: remove the unneeded result variable
fuse: port to vfs{g,u}id_t and associated helpers
fuse: Remove user_ns check for FUSE_DEV_IOC_CLONE
fuse: always revalidate rename target dentry
fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY
fs/fuse: Replace kmap() with kmap_local_page()
This is a followup to a previous commit of mine [0], which added the
allow_sys_admin_access && capable(CAP_SYS_ADMIN) check. This patch
rearranges the order of checks in fuse_allow_current_process without
changing functionality.
Commit 9ccf47b26b ("fuse: Add module param for CAP_SYS_ADMIN access
bypassing allow_other") added allow_sys_admin_access &&
capable(CAP_SYS_ADMIN) check to the beginning of the function, with the
reasoning that allow_sys_admin_access should be an 'escape hatch' for users
with CAP_SYS_ADMIN, allowing them to skip any subsequent checks.
However, placing this new check first results in many capable() calls when
allow_sys_admin_access is set, where another check would've also returned
1. This can be problematic when a BPF program is tracing capable() calls.
At Meta we ran into such a scenario recently. On a host where
allow_sys_admin_access is set but most of the FUSE access is from processes
which would pass other checks - i.e. they don't need CAP_SYS_ADMIN 'escape
hatch' - this results in an unnecessary capable() call for each fs op. We
also have a daemon tracing capable() with BPF and doing some data
collection, so tracing these extraneous capable() calls has the potential
to regress performance for an application doing many FUSE ops.
So rearrange the order of these checks such that CAP_SYS_ADMIN 'escape
hatch' is checked last. Add a small helper, fuse_permissible_uidgid, to
make the logic easier to understand. Previously, if allow_other is set on
the fuse_conn, uid/git checking doesn't happen as current_in_userns result
is returned. These semantics are maintained here: fuse_permissible_uidgid
check only happens if allow_other is not set.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The previous commit df8629af29 ("fuse: always revalidate if exclusive
create") ensures that the dentries are revalidated on O_EXCL creates. This
commit complements it by also performing revalidation for rename target
dentries. Otherwise, a rename target file that only exists in kernel
dentry cache but not in the filesystem will result in EEXIST if
RENAME_NOREPLACE flag is used.
Signed-off-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Signed-off-by: Zhang Tianci <zhangtianci.1997@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Add a flag to entry expiration that lets the filesystem expire a dentry
without kicking it out from the cache immediately.
This makes a difference for overmounted dentries, where plain invalidation
would detach all submounts before dropping the dentry from the cache. If
only expiry is set on the dentry, then any overmounts are left alone and
until ->d_revalidate() is called.
Note: ->d_revalidate() is not called for the case of following a submount,
so invalidation will only be triggered for the non-overmounted case. The
dentry could also be mounted in a different mount instance, in which case
any submounts will still be detached.
Suggested-by: Jakob Blomer <jblomer@cern.ch>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].
The current inode operation for getting posix acls takes an inode
argument but various filesystems (e.g., 9p, cifs, overlayfs) need access
to the dentry. In contrast to the ->set_acl() inode operation we cannot
simply extend ->get_acl() to take a dentry argument. The ->get_acl()
inode operation is called from:
acl_permission_check()
-> check_acl()
-> get_acl()
which is part of generic_permission() which in turn is part of
inode_permission(). Both generic_permission() and inode_permission() are
called in the ->permission() handler of various filesystems (e.g.,
overlayfs). So simply passing a dentry argument to ->get_acl() would
amount to also having to pass a dentry argument to ->permission(). We
should avoid this unnecessary change.
So instead of extending the existing inode operation rename it from
->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that
passes a dentry argument and which filesystems that need access to the
dentry can implement instead of ->get_inode_acl(). Filesystems like cifs
which allow setting and getting posix acls but not using them for
permission checking during lookup can simply not implement
->get_inode_acl().
This is intended to be a non-functional change.
Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Suggested-by/Inspired-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
This is basically equivalent to the FUSE_CREATE operation which creates and
opens a regular file.
Add a new FUSE_TMPFILE operation, otherwise just reuse the protocol and the
code for FUSE_CREATE.
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Since commit 73f03c2b4b ("fuse: Restrict allow_other to the superblock's
namespace or a descendant"), access to allow_other FUSE filesystems has
been limited to users in the mounting user namespace or descendants. This
prevents a process that is privileged in its userns - but not its parent
namespaces - from mounting a FUSE fs w/ allow_other that is accessible to
processes in parent namespaces.
While this restriction makes sense overall it breaks a legitimate usecase:
I have a tracing daemon which needs to peek into process' open files in
order to symbolicate - similar to 'perf'. The daemon is a privileged
process in the root userns, but is unable to peek into FUSE filesystems
mounted by processes in child namespaces.
This patch adds a module param, allow_sys_admin_access, to act as an escape
hatch for this descendant userns logic and for the allow_other mount option
in general. Setting allow_sys_admin_access allows processes with
CAP_SYS_ADMIN in the initial userns to access FUSE filesystems irrespective
of the mounting userns or whether allow_other was set. A sysadmin setting
this param must trust FUSEs on the host to not DoS processes as described
in 73f03c2b4b.
Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_finish_open() will be called with FUSE_NOWRITE set in case of atomic
O_TRUNC open(), so commit 76224355db ("fuse: truncate pagecache on
atomic_o_trunc") replaced invalidate_inode_pages2() by truncate_pagecache()
in such a case to avoid the A-A deadlock. However, we found another A-B-B-A
deadlock related to the case above, which will cause the xfstests
generic/464 testcase hung in our virtio-fs test environment.
For example, consider two processes concurrently open one same file, one
with O_TRUNC and another without O_TRUNC. The deadlock case is described
below, if open(O_TRUNC) is already set_nowrite(acquired A), and is trying
to lock a page (acquiring B), open() could have held the page lock
(acquired B), and waiting on the page writeback (acquiring A). This would
lead to deadlocks.
open(O_TRUNC)
----------------------------------------------------------------
fuse_open_common
inode_lock [C acquire]
fuse_set_nowrite [A acquire]
fuse_finish_open
truncate_pagecache
lock_page [B acquire]
truncate_inode_page
unlock_page [B release]
fuse_release_nowrite [A release]
inode_unlock [C release]
----------------------------------------------------------------
open()
----------------------------------------------------------------
fuse_open_common
fuse_finish_open
invalidate_inode_pages2
lock_page [B acquire]
fuse_launder_page
fuse_wait_on_page_writeback [A acquire & release]
unlock_page [B release]
----------------------------------------------------------------
Besides this case, all calls of invalidate_inode_pages2() and
invalidate_inode_pages2_range() in fuse code also can deadlock with
open(O_TRUNC).
Fix by moving the truncate_pagecache() call outside the nowrite protected
region. The nowrite protection is only for delayed writeback
(writeback_cache) case, where inode lock does not protect against
truncation racing with writes on the server. Write syscalls racing with
page cache truncation still get the inode lock protection.
This patch also changes the order of filemap_invalidate_lock()
vs. fuse_set_nowrite() in fuse_open_common(). This new order matches the
order found in fuse_file_fallocate() and fuse_do_setattr().
Reported-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Tested-by: Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>
Fixes: e4648309b8 ("fuse: truncate pending writes on O_TRUNC")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This is a "weak" conversion which converts straight back to using pages.
A full conversion should be performed at some point, hopefully by
someone familiar with the filesystem.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Straightforward conversion although the helper functions still assume
a single page.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Tested-by: Mike Marshall <hubcap@omnibond.com> # orangefs
Tested-by: David Howells <dhowells@redhat.com> # afs
When a new inode is created, send its security context to server along with
creation request (FUSE_CREAT, FUSE_MKNOD, FUSE_MKDIR and FUSE_SYMLINK).
This gives server an opportunity to create new file and set security
context (possibly atomically). In all the configurations it might not be
possible to set context atomically.
Like nfs and ceph, use security_dentry_init_security() to dermine security
context of inode and send it with create, mkdir, mknod, and symlink
requests.
Following is the information sent to server.
fuse_sectx_header, fuse_secctx, xattr_name, security_context
- struct fuse_secctx_header
This contains total number of security contexts being sent and total
size of all the security contexts (including size of
fuse_secctx_header).
- struct fuse_secctx
This contains size of security context which follows this structure.
There is one fuse_secctx instance per security context.
- xattr name string
This string represents name of xattr which should be used while setting
security context.
- security context
This is the actual security context whose size is specified in
fuse_secctx struct.
Also add the FUSE_SECURITY_CTX flag for the `flags` field of the
fuse_init_out struct. When this flag is set the kernel will append the
security context for a newly created inode to the request (create, mkdir,
mknod, and symlink). The server is responsible for ensuring that the inode
appears atomically (preferrably) with the requested security context.
For example, If the server is using SELinux and backed by a "real" linux
file system that supports extended attributes it can write the security
context value to /proc/thread-self/attr/fscreate before making the syscall
to create the inode.
This patch is based on patch from Chirantan Ekbote <chirantan@chromium.org>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fuse_update_attributes() refreshes metadata for internal use.
Each use needs a particular set of attributes to be refreshed, but
currently that cannot be expressed and all but atime are refreshed.
Add a mask argument, which lets fuse_update_get_attr() to decide based on
the cache_mask and the inval_mask whether a GETATTR call is needed or not.
Reported-by: Yongji Xie <xieyongji@bytedance.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
When deciding to send a GETATTR request take into account the cache mask
(which attributes are always valid). The cache mask takes precedence over
the invalid mask.
This results in the GETATTR request not being sent unnecessarily.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If writeback_cache is enabled, then the size, mtime and ctime attributes of
regular files are always valid in the kernel's cache. They are retrieved
from userspace only when the inode is freshly looked up.
Add a more generic "cache_mask", that indicates which attributes are
currently valid in cache.
This patch doesn't change behavior.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
In case of writeback_cache fuse_fillattr() would revert the queried
attributes to the cached version.
Move this to fuse_change_attributes() in order to manage the writeback
logic in a central helper. This will be necessary for patches that follow.
Only fuse_do_getattr() -> fuse_fillattr() uses the attributes after calling
fuse_change_attributes(), so this should not change behavior.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
There are two instances of "bool is_wb = fc->writeback_cache" where the
actual use mostly involves checking "is_wb && S_ISREG(inode->i_mode)".
Clean up these cases by storing the second condition in the local variable.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Only invalidate attributes that the operation might have changed.
Introduce two constants for common combinations of changed attributes:
FUSE_STATX_MODIFY: file contents are modified but not size
FUSE_STATX_MODSIZE: size and/or file contents modified
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
The fuse_iget() call in create_new_entry() already updated the inode with
all the new attributes and incremented the attribute version.
Incrementing the nlink will result in the wrong count. This wasn't noticed
because the attributes were invalidated right after this.
Updating ctime is still needed for the writeback case when the ctime is not
refreshed.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Rename didn't decrement/clear nlink on overwritten target inode.
Create a common helper fuse_entry_unlinked() that handles this for unlink,
rmdir and rename.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Logically it belongs there since attributes are invalidated due to the
updated ctime. This is a cleanup and should not change behavior.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
In writeback cache mode mtime/ctime updates are cached, and flushed to the
server using the ->write_inode() callback.
Closing the file will result in a dirty inode being immediately written,
but in other cases the inode can remain dirty after all references are
dropped. This result in the inode being written back from reclaim, which
can deadlock on a regular allocation while the request is being served.
The usual mechanisms (GFP_NOFS/PF_MEMALLOC*) don't work for FUSE, because
serving a request involves unrelated userspace process(es).
Instead do the same as for dirty pages: make sure the inode is written
before the last reference is gone.
- fallocate(2)/copy_file_range(2): these call file_update_time() or
file_modified(), so flush the inode before returning from the call
- unlink(2), link(2) and rename(2): these call fuse_update_ctime(), so
flush the ctime directly from this helper
Reported-by: chenguanyou <chenguanyou@xiaomi.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Use invalidate_lock instead of fuse's private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we fix a long standing
race between hole punching and read(2) / readahead(2) paths that can
lead to stale page cache contents.
CC: Miklos Szeredi <miklos@szeredi.hu>
Reviewed-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Server responds to LOOKUP and other ops (READDIRPLUS/CREATE/MKNOD/...)
with ourarg containing nodeid and generation.
If a fuse inode is found in inode cache with the same nodeid but different
generation, the existing fuse inode should be unhashed and marked "bad" and
a new inode with the new generation should be hashed instead.
This can happen, for example, with passhrough fuse filesystem that returns
the real filesystem ino/generation on lookup and where real inode numbers
can get recycled due to real files being unlinked not via the fuse
passthrough filesystem.
With current code, this situation will not be detected and an old fuse
dentry that used to point to an older generation real inode, can be used to
access a completely new inode, which should be accessed only via the new
dentry.
Note that because the FORGET message carries the nodeid w/o generation, the
server should wait to get FORGET counts for the nlookup counts of the old
and reused inodes combined, before it can free the resources associated to
that nodeid.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
fc_mount() already handles the vfs_get_tree(), sb->s_umount
unlocking and vfs_create_mount() sequence. Using it greatly
simplifies fuse_dentry_automount().
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
We recently fixed an infinite loop by setting the SB_BORN flag on
submounts along with the write barrier needed by super_cache_count().
This is the job of vfs_get_tree() and FUSE shouldn't have to care
about the barrier at all.
Split out some code from fuse_dentry_automount() to the dedicated
fuse_get_tree_submount() handler for submounts and call vfs_get_tree().
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
We don't set the SB_BORN flag on submounts. This is wrong as these
superblocks are then considered as partially constructed or dying
in the rest of the code and can break some assumptions.
One such case is when you have a virtiofs filesystem with submounts
and you try to mount it again : virtio_fs_get_tree() tries to obtain
a superblock with sget_fc(). The logic in sget_fc() is to loop until
it has either found an existing matching superblock with SB_BORN set
or to create a brand new one. It is assumed that a superblock without
SB_BORN is transient and the loop is restarted. Forgetting to set
SB_BORN on submounts hence causes sget_fc() to retry forever.
Setting SB_BORN requires special care, i.e. a write barrier for
super_cache_count() which can check SB_BORN without taking any lock.
We should call vfs_get_tree() to deal with that but this requires
to have a proper ->get_tree() implementation for submounts, which
is a bigger piece of work. Go for a simple bug fix in the meatime.
Fixes: bf109c6404 ("fuse: implement crossmounts")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the
superblock can theoretically be killed. If this happens before the
submount was added to the &fc->mounts list, fuse_mount_remove() later
crashes in list_del_init() because it assumes the submount to be
already there.
Add the submount before dropping sb->s_umount to fix the inconsistency.
It is okay to nest fc->killsb under sb->s_umount, we already do this
on the ->kill_sb() path.
Signed-off-by: Greg Kurz <groug@kaod.org>
Fixes: bf109c6404 ("fuse: implement crossmounts")
Cc: stable@vger.kernel.org # v5.10+
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If fuse_fill_super_submount() returns an error, the error path
triggers a crash:
[ 26.206673] BUG: kernel NULL pointer dereference, address: 0000000000000000
[...]
[ 26.226362] RIP: 0010:__list_del_entry_valid+0x25/0x90
[...]
[ 26.247938] Call Trace:
[ 26.248300] fuse_mount_remove+0x2c/0x70 [fuse]
[ 26.248892] virtio_kill_sb+0x22/0x160 [virtiofs]
[ 26.249487] deactivate_locked_super+0x36/0xa0
[ 26.250077] fuse_dentry_automount+0x178/0x1a0 [fuse]
The crash happens because fuse_mount_remove() assumes that the FUSE
mount was already added to list under the FUSE connection, but this
only done after fuse_fill_super_submount() has returned success.
This means that until fuse_fill_super_submount() has returned success,
the FUSE mount isn't actually owned by the superblock. We should thus
reclaim ownership by clearing sb->s_fs_info, which will skip the call
to fuse_mount_remove(), and perform rollback, like virtio_fs_get_tree()
already does for the root sb.
Fixes: bf109c6404 ("fuse: implement crossmounts")
Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Pull fileattr conversion updates from Miklos Szeredi via Al Viro:
"This splits the handling of FS_IOC_[GS]ETFLAGS from ->ioctl() into a
separate method.
The interface is reasonably uniform across the filesystems that
support it and gives nice boilerplate removal"
* 'miklos.fileattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (23 commits)
ovl: remove unneeded ioctls
fuse: convert to fileattr
fuse: add internal open/release helpers
fuse: unsigned open flags
fuse: move ioctl to separate source file
vfs: remove unused ioctl helpers
ubifs: convert to fileattr
reiserfs: convert to fileattr
ocfs2: convert to fileattr
nilfs2: convert to fileattr
jfs: convert to fileattr
hfsplus: convert to fileattr
efivars: convert to fileattr
xfs: convert to fileattr
orangefs: convert to fileattr
gfs2: convert to fileattr
f2fs: convert to fileattr
ext4: convert to fileattr
ext2: convert to fileattr
btrfs: convert to fileattr
...
Since fuse just passes ioctl args through to/from server, converting to the
fileattr API is more involved, than most other filesystems.
Both .fileattr_set() and .fileattr_get() need to obtain an open file to
operate on. The simplest way is with the following sequence:
FUSE_OPEN
FUSE_IOCTL
FUSE_RELEASE
If this turns out to be a performance problem, it could be optimized for
the case when there's already a file (any file) open for the inode.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
inode_wrong_type(inode, mode) returns true if setting inode->i_mode
to given value would've changed the inode type. We have enough of
those checks open-coded to make a helper worthwhile.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Extend some inode methods with an additional user namespace argument. A
filesystem that is aware of idmapped mounts will receive the user
namespace the mount has been marked with. This can be used for
additional permission checking and also to enable filesystems to
translate between uids and gids if they need to. We have implemented all
relevant helpers in earlier patches.
As requested we simply extend the exisiting inode method instead of
introducing new ones. This is a little more code churn but it's mostly
mechanical and doesnt't leave us with additional inode methods.
Link: https://lore.kernel.org/r/20210121131959.646623-25-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The generic_fillattr() helper fills in the basic attributes associated
with an inode. Enable it to handle idmapped mounts. If the inode is
accessed through an idmapped mount map it into the mount's user
namespace before we store the uid and gid. If the initial user namespace
is passed nothing changes so non-idmapped mounts will see identical
behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-12-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
When file attributes are changed most filesystems rely on the
setattr_prepare(), setattr_copy(), and notify_change() helpers for
initialization and permission checking. Let them handle idmapped mounts.
If the inode is accessed through an idmapped mount map it into the
mount's user namespace. Afterwards the checks are identical to
non-idmapped mounts. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.
Helpers that perform checks on the ia_uid and ia_gid fields in struct
iattr assume that ia_uid and ia_gid are intended values and have already
been mapped correctly at the userspace-kernelspace boundary as we
already do today. If the initial user namespace is passed nothing
changes so non-idmapped mounts will see identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-8-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The two helpers inode_permission() and generic_permission() are used by
the vfs to perform basic permission checking by verifying that the
caller is privileged over an inode. In order to handle idmapped mounts
we extend the two helpers with an additional user namespace argument.
On idmapped mounts the two helpers will make sure to map the inode
according to the mount's user namespace and then peform identical
permission checks to inode_permission() and generic_permission(). If the
initial user namespace is passed nothing changes so non-idmapped mounts
will see identical behavior as before.
Link: https://lore.kernel.org/r/20210121131959.646623-6-christian.brauner@ubuntu.com
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Jan Kara's analysis of the syzbot report (edited):
The reproducer opens a directory on FUSE filesystem, it then attaches
dnotify mark to the open directory. After that a fuse_do_getattr() call
finds that attributes returned by the server are inconsistent, and calls
make_bad_inode() which, among other things does:
inode->i_mode = S_IFREG;
This then confuses dnotify which doesn't tear down its structures
properly and eventually crashes.
Avoid calling make_bad_inode() on a live inode: switch to a private flag on
the fuse inode. Also add the test to ops which the bad_inode_ops would
have caught.
This bug goes back to the initial merge of fuse in 2.6.14...
Reported-by: syzbot+f427adf9324b92652ccc@syzkaller.appspotmail.com
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Tested-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
With FUSE_HANDLE_KILLPRIV_V2 support, server will need to kill suid/sgid/
security.capability on open(O_TRUNC), if server supports
FUSE_ATOMIC_O_TRUNC.
But server needs to kill suid/sgid only if caller does not have CAP_FSETID.
Given server does not have this information, client needs to send this info
to server.
So add a flag FUSE_OPEN_KILL_SUIDGID to fuse_open_in request which tells
server to kill suid/sgid (only if group execute is set).
This flag is added to the FUSE_OPEN request, as well as the FUSE_CREATE
request if the create was non-exclusive, since that might result in an
existing file being opened/truncated.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If client does a write() on a suid/sgid file, VFS will first call
fuse_setattr() with ATTR_KILL_S[UG]ID set. This requires sending setattr
to file server with ATTR_MODE set to kill suid/sgid. But to do that client
needs to know latest mode otherwise it is racy.
To reduce the race window, current code first call fuse_do_getattr() to get
latest ->i_mode and then resets suid/sgid bits and sends rest to server
with setattr(ATTR_MODE). This does not reduce the race completely but
narrows race window significantly.
With fc->handle_killpriv_v2 enabled, it should be possible to remove this
race completely. Do not kill suid/sgid with ATTR_MODE at all. It will be
killed by server when WRITE request is sent to server soon. This is
similar to fc->handle_killpriv logic. V2 is just more refined version of
protocol. Hence this patch does not send ATTR_MODE to kill suid/sgid if
fc->handle_killpriv_v2 is enabled.
This creates an issue if fc->writeback_cache is enabled. In that case
WRITE can be cached in guest and server might not see WRITE request and
hence will not kill suid/sgid. Miklos suggested that in such cases, we
should fallback to a writethrough WRITE instead and that will generate
WRITE request and kill suid/sgid. This patch implements that too.
But this relies on client seeing the suid/sgid set. If another client sets
suid/sgid and this client does not see it immideately, then we will not
fallback to writethrough WRITE. So this is one limitation with both
fc->handle_killpriv_v2 and fc->writeback_cache enabled. Both the options
are not fully compatible. But might be good enough for many use cases.
Note: This patch is not checking whether security.capability is set or not
when falling back to writethrough path. If suid/sgid is not set and
only security.capability is set, that will be taken care of by
file_remove_privs() call in ->writeback_cache path.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
If fc->handle_killpriv_v2 is enabled, we expect file server to clear
suid/sgid/security.capbility upon chown/truncate/write as appropriate.
Upon truncate (ATTR_SIZE), suid/sgid are cleared only if caller does not
have CAP_FSETID. File server does not know whether caller has CAP_FSETID
or not. Hence set FATTR_KILL_SUIDGID upon truncate to let file server know
that caller does not have CAP_FSETID and it should kill suid/sgid as
appropriate.
On chown (ATTR_UID/ATTR_GID) suid/sgid need to be cleared irrespective of
capabilities of calling process, so set FATTR_KILL_SUIDGID unconditionally
in that case.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Failure to do so may result in EEXIST even if the file only exists in the
cache and not in the filesystem.
The atomic nature of O_EXCL mandates that the cached state should be
ignored and existence verified anew.
Reported-by: Ken Schalk <kschalk@nvidia.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fuse mount now only ever has a refcount of one (before being freed) so the
count field is unnecessary.
Remove the refcounting and fold fuse_mount_put() into callers. The only
caller of fuse_mount_put() where fm->fc was NULL is fuse_dentry_automount()
and here the fuse_conn_put() can simply be omitted.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
FUSE servers can indicate crossmount points by setting FUSE_ATTR_SUBMOUNT
in fuse_attr.flags. The inode will then be marked as S_AUTOMOUNT, and the
.d_automount implementation creates a new submount at that location, so
that the submount gets a distinct st_dev value.
Note that all submounts get a distinct superblock and a distinct st_dev
value, so for virtio-fs, even if the same filesystem is mounted more than
once on the host, none of its mount points will have the same st_dev. We
need distinct superblocks because the superblock points to the root node,
but the different host mounts may show different trees (e.g. due to
submounts in some of them, but not in others).
Right now, this behavior is only enabled when fuse_conn.auto_submounts is
set, which is the case only for virtio-fs.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
We want to allow submounts for the same fuse_conn, but with different
superblocks so that each of the submounts has its own device ID. To do
so, we need to split all mount-specific information off of fuse_conn
into a new fuse_mount structure, so that multiple mounts can share a
single fuse_conn.
We need to take care only to perform connection-level actions once (i.e.
when the fuse_conn and thus the first fuse_mount are established, or
when the last fuse_mount and thus the fuse_conn are destroyed). For
example, fuse_sb_destroy() must invoke fuse_send_destroy() until the
last superblock is released.
To do so, we keep track of which fuse_mount is the root mount and
perform all fuse_conn-level actions only when this fuse_mount is
involved.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Currently in fuse we don't seem have any lock which can serialize fault
path with truncate/punch_hole path. With dax support I need one for
following reasons.
1. Dax requirement
DAX fault code relies on inode size being stable for the duration of
fault and want to serialize with truncate/punch_hole and they explicitly
mention it.
static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
const struct iomap_ops *ops)
/*
* Check whether offset isn't beyond end of file now. Caller is
* supposed to hold locks serializing us with truncate / punch hole so
* this is a reliable test.
*/
max_pgoff = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2. Make sure there are no users of pages being truncated/punch_hole
get_user_pages() might take references to page and then do some DMA
to said pages. Filesystem might truncate those pages without knowing
that a DMA is in progress or some I/O is in progress. So use
dax_layout_busy_page() to make sure there are no such references
and I/O is not in progress on said pages before moving ahead with
truncation.
3. Limitation of kvm page fault error reporting
If we are truncating file on host first and then removing mappings in
guest lateter (truncate page cache etc), then this could lead to a
problem with KVM. Say a mapping is in place in guest and truncation
happens on host. Now if guest accesses that mapping, then host will
take a fault and kvm will either exit to qemu or spin infinitely.
IOW, before we do truncation on host, we need to make sure that guest
inode does not have any mapping in that region or whole file.
4. virtiofs memory range reclaim
Soon I will introduce the notion of being able to reclaim dax memory
ranges from a fuse dax inode. There also I need to make sure that
no I/O or fault is going on in the reclaimed range and nobody is using
it so that range can be reclaimed without issues.
Currently if we take inode lock, that serializes read/write. But it does
not do anything for faults. So I add another semaphore fuse_inode->i_mmap_sem
for this purpose. It can be used to serialize with faults.
As of now, I am adding taking this semaphore only in dax fault path and
not regular fault path because existing code does not have one. May
be existing code can benefit from it as well to take care of some
races, but that we can fix later if need be. For now, I am just focussing
only on DAX path which is new path.
Also added logic to take fuse_inode->i_mmap_sem in
truncate/punch_hole/open(O_TRUNC) path to make sure file truncation and
fuse dax fault are mutually exlusive and avoid all the above problems.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fuse mounts without "allow_other" are off-limits to all non-owners. Yet it
makes sense to allow querying st_dev on the root, since this value is
provided by the kernel, not the userspace filesystem.
Allow statx(2) with a zero request mask to succeed on a fuse mounts for all
users.
Reported-by: Nikolaus Rath <Nikolaus@rath.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Allow fuse to pass RENAME_WHITEOUT to fuse server. Overlayfs on top of
virtiofs uses RENAME_WHITEOUT.
Without this patch renaming a directory in overlayfs (dir is on lower)
fails with -EINVAL. With this patch it works.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
