linux.git/fs/super.c, branch v5.1

[fix] get rid of checking for absent device name in vfs_get_tree()

2019-04-29T01:34:21+00:00

It has no business being there, it's checked by relevant ->get_tree()
as it is *and* it returns the wrong error for no reason whatsoever.

Fixes: f3a09c92018a "introduce fs_context methods"
Signed-off-by: Al Viro

vfs: Add some logging to the core users of the fs_context log

2019-02-28T08:29:38+00:00

Add some logging to the core users of the fs_context log so that
information can be extracted from them as to the reason for failure.

Signed-off-by: David Howells 
Signed-off-by: Al Viro

convenience helpers: vfs_get_super() and sget_fc()

2019-02-28T08:29:26+00:00

the former is an analogue of mount_{single,nodev} for use in
->get_tree() instances, the latter - analogue of sget() for the
same.

These are fairly similar to the originals, but the callback signature
for sget_fc() is different from sget() ones, so getting bits and
pieces shared would be too convoluted; we might get around to that
later, but for now let's just remember to keep them in sync.  They
do live next to each other, and changes in either won't be hard
to spot.

Signed-off-by: Al Viro

introduce fs_context methods

2019-01-30T22:44:27+00:00

Signed-off-by: Al Viro

convert do_remount_sb() to fs_context

2019-01-30T22:44:26+00:00

Replace do_remount_sb() with a function, reconfigure_super(), that's
fs_context aware.  The fs_context is expected to be parameterised already
and have ->root pointing to the superblock to be reconfigured.

A legacy wrapper is provided that is intended to be called from the
fs_context ops when those appear, but for now is called directly from
reconfigure_super().  This wrapper invokes the ->remount_fs() superblock op
for the moment.  It is intended that the remount_fs() op will be phased
out.

The fs_context->purpose is set to FS_CONTEXT_FOR_RECONFIGURE to indicate
that the context is being used for reconfiguration.

do_umount_root() is provided to consolidate remount-to-R/O for umount and
emergency remount by creating a context and invoking reconfiguration.

do_remount(), do_umount() and do_emergency_remount_callback() are switched
to use the new process.

[AV -- fold UMOUNT and EMERGENCY_REMOUNT in; fixes the
umount / bug, gets rid of pointless complexity]
[AV -- set ->net_ns in all cases; nfs remount will need that]
[AV -- shift security_sb_remount() call into reconfigure_super(); the callers
that didn't do security_sb_remount() have NULL fc->security anyway, so it's
a no-op for them]

Signed-off-by: David Howells 
Co-developed-by: Al Viro 
Signed-off-by: Al Viro

vfs_get_tree(): evict the call of security_sb_kern_mount()

2019-01-30T22:44:26+00:00

Right now vfs_get_tree() calls security_sb_kern_mount() (i.e.
mount MAC) unless it gets MS_KERNMOUNT or MS_SUBMOUNT in flags.
Doing it that way is both clumsy and imprecise.

Consider the callers' tree of vfs_get_tree():
vfs_get_tree()
        <- do_new_mount()
	<- vfs_kern_mount()
		<- simple_pin_fs()
		<- vfs_submount()
		<- kern_mount_data()
		<- init_mount_tree()
		<- btrfs_mount()
			<- vfs_get_tree()
		<- nfs_do_root_mount()
			<- nfs4_try_mount()
				<- nfs_fs_mount()
					<- vfs_get_tree()
			<- nfs4_referral_mount()

do_new_mount() always does need MAC (we are guaranteed that neither
MS_KERNMOUNT nor MS_SUBMOUNT will be passed there).

simple_pin_fs(), vfs_submount() and kern_mount_data() pass explicit
flags inhibiting that check.  So does nfs4_referral_mount() (the
flags there are ulimately coming from vfs_submount()).

init_mount_tree() is called too early for anything LSM-related; it
doesn't matter whether we attempt those checks, they'll do nothing.

Finally, in case of btrfs_mount() and nfs_fs_mount(), doing MAC
is pointless - either the caller will do it, or the flags are
such that we wouldn't have done it either.

In other words, the one and only case when we want that check
done is when we are called from do_new_mount(), and there we
want it unconditionally.

So let's simply move it there.  The superblock is still locked,
so nobody is going to get access to it (via ustat(2), etc.)
until we get a chance to apply the checks - we are free to
move them to any point up to where we drop ->s_umount (in
do_new_mount_fc()).

Signed-off-by: Al Viro

teach vfs_get_tree() to handle subtype, switch do_new_mount() to it

2019-01-30T22:44:25+00:00

Roll the handling of subtypes into do_new_mount() and vfs_get_tree().  The
former determines any subtype string and hangs it off the fs_context; the
latter applies it.

Make do_new_mount() create, parameterise and commit an fs_context and
create a mount for itself rather than calling vfs_kern_mount().

[AV -- missing kstrdup()]
[AV -- ... and no kstrdup() if we get to setting ->s_submount - we
simply transfer it from fc, leaving NULL behind]
[AV -- constify ->s_submount, while we are at it]

Reviewed-by: David Howells 
Signed-off-by: Al Viro

vfs: Introduce fs_context, switch vfs_kern_mount() to it.

2019-01-30T22:44:23+00:00

Introduce a filesystem context concept to be used during superblock
creation for mount and superblock reconfiguration for remount.  This is
allocated at the beginning of the mount procedure and into it is placed:

 (1) Filesystem type.

 (2) Namespaces.

 (3) Source/Device names (there may be multiple).

 (4) Superblock flags (SB_*).

 (5) Security details.

 (6) Filesystem-specific data, as set by the mount options.

Accessor functions are then provided to set up a context, parameterise it
from monolithic mount data (the data page passed to mount(2)) and tear it
down again.

A legacy wrapper is provided that implements what will be the basic
operations, wrapping access to filesystems that aren't yet aware of the
fs_context.

Finally, vfs_kern_mount() is changed to make use of the fs_context and
mount_fs() is replaced by vfs_get_tree(), called from vfs_kern_mount().
[AV -- add missing kstrdup()]
[AV -- put_cred() can be unconditional - fc->cred can't be NULL]
[AV -- take legacy_validate() contents into legacy_parse_monolithic()]
[AV -- merge KERNEL_MOUNT and USER_MOUNT]
[AV -- don't unlock superblock on success return from vfs_get_tree()]
[AV -- kill 'reference' argument of init_fs_context()]

Signed-off-by: David Howells 
Co-developed-by: Al Viro 
Signed-off-by: Al Viro

mount_fs: suppress MAC on MS_SUBMOUNT as well as MS_KERNMOUNT

2018-12-21T16:51:23+00:00

Reviewed-by: David Howells 
Signed-off-by: Al Viro

LSM: hide struct security_mnt_opts from any generic code

2018-12-21T16:48:34+00:00

Keep void * instead, allocate on demand (in parse_str_opts, at the
moment).  Eventually both selinux and smack will be better off
with private structures with several strings in those, rather than
this "counter and two pointers to dynamically allocated arrays"
ugliness.  This commit allows to do that at leisure, without
disrupting anything outside of given module.

Changes:
	* instead of struct security_mnt_opt use an opaque pointer
initialized to NULL.
	* security_sb_eat_lsm_opts(), security_sb_parse_opts_str() and
security_free_mnt_opts() take it as var argument (i.e. as void **);
call sites are unchanged.
	* security_sb_set_mnt_opts() and security_sb_remount() take
it by value (i.e. as void *).
	* new method: ->sb_free_mnt_opts().  Takes void *, does
whatever freeing that needs to be done.
	* ->sb_set_mnt_opts() and ->sb_remount() might get NULL as
mnt_opts argument, meaning "empty".

Reviewed-by: David Howells 
Signed-off-by: Al Viro