[ Upstream commit c8a139d001a1aab1ea8734db14b22dac9dd143b6 ]

ops->show() can return a negative error code.
Commit 65da3484d9be ("sysfs: correctly handle short reads on PREALLOC attrs.")
(in v4.4) caused this to be stored in an unsigned 'size_t' variable, so errors
would look like large numbers.
As a result, if an error is returned, sysfs_kf_read() will return the
value of 'count', typically 4096.

Commit 17d0774f8068 ("sysfs: correctly handle read offset on PREALLOC attrs")
(in v4.8) extended this error to use the unsigned large 'len' as a size for
memmove().
Consequently, if ->show returns an error, then the first read() on the
sysfs file will return 4096 and could return uninitialized memory to
user-space.
If the application performs a subsequent read, this will trigger a memmove()
with extremely large count, and is likely to crash the machine is bizarre ways.

This bug can currently only be triggered by reading from an md
sysfs attribute declared with __ATTR_PREALLOC() during the
brief period between when mddev_put() deletes an mddev from
the ->all_mddevs list, and when mddev_delayed_delete() - which is
scheduled on a workqueue - completes.
Before this, an error won't be returned by the ->show()
After this, the ->show() won't be called.

I can reproduce it reliably only by putting delay like
	usleep_range(500000,700000);
early in mddev_delayed_delete(). Then after creating an
md device md0 run
  echo clear > /sys/block/md0/md/array_state; cat /sys/block/md0/md/array_state

The bug can be triggered without the usleep.

Fixes: 65da3484d9be ("sysfs: correctly handle short reads on PREALLOC attrs.")
Fixes: 17d0774f8068 ("sysfs: correctly handle read offset on PREALLOC attrs")
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

[ Upstream commit 17d0774f80681020eccc9638d925a23f1fc4f671 ]

Attributes declared with __ATTR_PREALLOC use sysfs_kf_read() which returns
zero bytes for non-zero offset. This breaks script checkarray in mdadm tool
in debian where /bin/sh is 'dash' because its builtin 'read' reads only one
byte at a time. Script gets 'i' instead of 'idle' when reads current action
from /sys/block/$dev/md/sync_action and as a result does nothing.

This patch adds trivial implementation of partial read: generate whole
string and move required part into buffer head.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Fixes: 4ef67a8c95f3 ("sysfs/kernfs: make read requests on pre-alloc files use the buffer.")
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=787950
Cc: Stable <stable@vger.kernel.org> # v3.19+
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

[ Upstream commit 65da3484d9be5664f5f7d2378e438bb2794f40b8 ]

attributes declared with __ATTR_PREALLOC use sysfs_kf_read()
which ignores the 'count' arg.
So a 1-byte read request can return more bytes than that.

This is seen with the 'dash' shell when 'read' is used on
some 'md' sysfs attributes.

So only return the 'min' of count and the attribute length.

Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

commit 1b852bceb0d111e510d1a15826ecc4a19358d512 upstream.

Fresh mounts of proc and sysfs are a very special case that works very
much like a bind mount.  Unfortunately the current structure can not
preserve the MNT_LOCK... mount flags.  Therefore refactor the logic
into a form that can be modified to preserve those lock bits.

Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount
of the filesystem be fully visible in the current mount namespace,
before the filesystem may be mounted.

Move the logic for calling fs_fully_visible from proc and sysfs into
fs/namespace.c where it has greater access to mount namespace state.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 87d2846fcf88113fae2341da1ca9a71f0d916f2c upstream.

Add two functions sysfs_create_mount_point and
sysfs_remove_mount_point that hang a permanently empty directory off
of a kobject or remove a permanently emptpy directory hanging from a
kobject.  Export these new functions so modular filesystems can use
them.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

For sysfs file attributes, only read and write permissions make sense.
Mask provided attribute permissions accordingly and send a warning
to the console if invalid permission bits are set.

This patch is originally from Guenter [1] and includes the fixup
explained in the thread, that is printing permissions in octal format
and limiting the scope of attributes to SYSFS_PREALLOC | 0664.

[1] https://lkml.org/lkml/2015/1/19/599

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Up to now, is_visible can only be used to either remove visibility
of a file entirely or to add permissions, but not to reduce permissions.
This makes it impossible, for example, to use DEVICE_ATTR_RW to define
file attributes and reduce permissions to read-only.

This behavior is undesirable and unnecessarily complicates code which
needs to reduce permissions; instead of just returning the desired
permissions, it has to ensure that the permissions in the attribute
variable declaration only reflect the minimal permissions ever needed.

Change semantics of is_visible to only use the permissions returned
from it instead of oring the returned value with the hard-coded
permissions.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull driver core patches from Greg KH:
 "Really tiny set of patches for this kernel.  Nothing major, all
  described in the shortlog and have been in linux-next for a while"

* tag 'driver-core-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  sysfs: fix warning when creating a sysfs group without attributes
  firmware_loader: handle timeout via wait_for_completion_interruptible_timeout()
  firmware_loader: abort request if wait_for_completion is interrupted
  firmware: Correct function name in comment
  device: Change dev_<level> logging functions to return void
  device: Fix dev_dbg_once macro

When a new kernfs node is created, KERNFS_STATIC_NAME is used to avoid
making a separate copy of its name.  It's currently only used for sysfs
attributes whose filenames are required to stay accessible and unchanged.
There are rare exceptions where these names are allocated and formatted
dynamically but for the vast majority of cases they're consts in the
rodata section.

Now that kernfs is converted to use kstrdup_const() and kfree_const(),
there's little point in keeping KERNFS_STATIC_NAME around.  Remove it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When attempting to create a gropu without attrs, the warning prints the
name of the group.  However, the check for name being a NULL pointer is
wrong: it uses the pointer to the name when it's NULL.  Fix it to use
the name if present, otherwise just put an empty string.

Cc: Bruno Prémont <bonbons@linux-vserver.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>