linux-stable.git/fs, branch v4.4.183

Abort file_remove_privs() for non-reg. files

2019-06-22T06:18:27+00:00

commit f69e749a49353d96af1a293f56b5b56de59c668a upstream.

file_remove_privs() might be called for non-regular files, e.g.
blkdev inode. There is no reason to do its job on things
like blkdev inodes, pipes, or cdevs. Hence, abort if
file does not refer to a regular inode.

AV: more to the point, for devices there might be any number of
inodes refering to given device.  Which one to strip the permissions
from, even if that made any sense in the first place?  All of them
will be observed with contents modified, after all.

Found by LockDoc (Alexander Lochmann, Horst Schirmeier and Olaf
Spinczyk)

Reviewed-by: Jan Kara 
Signed-off-by: Alexander Lochmann 
Signed-off-by: Horst Schirmeier 
Signed-off-by: Al Viro 
Cc: Zubin Mithra 
Signed-off-by: Greg Kroah-Hartman

coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping

2019-06-22T06:18:27+00:00

commit 04f5866e41fb70690e28397487d8bd8eea7d712a upstream.

The core dumping code has always run without holding the mmap_sem for
writing, despite that is the only way to ensure that the entire vma
layout will not change from under it.  Only using some signal
serialization on the processes belonging to the mm is not nearly enough.
This was pointed out earlier.  For example in Hugh's post from Jul 2017:

  https://lkml.kernel.org/r/alpine.LSU.2.11.1707191716030.2055@eggly.anvils

  "Not strictly relevant here, but a related note: I was very surprised
   to discover, only quite recently, how handle_mm_fault() may be called
   without down_read(mmap_sem) - when core dumping. That seems a
   misguided optimization to me, which would also be nice to correct"

In particular because the growsdown and growsup can move the
vm_start/vm_end the various loops the core dump does around the vma will
not be consistent if page faults can happen concurrently.

Pretty much all users calling mmget_not_zero()/get_task_mm() and then
taking the mmap_sem had the potential to introduce unexpected side
effects in the core dumping code.

Adding mmap_sem for writing around the ->core_dump invocation is a
viable long term fix, but it requires removing all copy user and page
faults and to replace them with get_dump_page() for all binary formats
which is not suitable as a short term fix.

For the time being this solution manually covers the places that can
confuse the core dump either by altering the vma layout or the vma flags
while it runs.  Once ->core_dump runs under mmap_sem for writing the
function mmget_still_valid() can be dropped.

Allowing mmap_sem protected sections to run in parallel with the
coredump provides some minor parallelism advantage to the swapoff code
(which seems to be safe enough by never mangling any vma field and can
keep doing swapins in parallel to the core dumping) and to some other
corner case.

In order to facilitate the backporting I added "Fixes: 86039bd3b4e6"
however the side effect of this same race condition in /proc/pid/mem
should be reproducible since before 2.6.12-rc2 so I couldn't add any
other "Fixes:" because there's no hash beyond the git genesis commit.

Because find_extend_vma() is the only location outside of the process
context that could modify the "mm" structures under mmap_sem for
reading, by adding the mmget_still_valid() check to it, all other cases
that take the mmap_sem for reading don't need the new check after
mmget_not_zero()/get_task_mm().  The expand_stack() in page fault
context also doesn't need the new check, because all tasks under core
dumping are frozen.

Link: http://lkml.kernel.org/r/20190325224949.11068-1-aarcange@redhat.com
Fixes: 86039bd3b4e6 ("userfaultfd: add new syscall to provide memory externalization")
Signed-off-by: Andrea Arcangeli 
Reported-by: Jann Horn 
Suggested-by: Oleg Nesterov 
Acked-by: Peter Xu 
Reviewed-by: Mike Rapoport 
Reviewed-by: Oleg Nesterov 
Reviewed-by: Jann Horn 
Acked-by: Jason Gunthorpe 
Acked-by: Michal Hocko 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Cc: Joel Fernandes (Google) 
[mhocko@suse.com: stable 4.4 backport
 - drop infiniband part because of missing 5f9794dc94f59
 - drop userfaultfd_event_wait_completion hunk because of
   missing 9cd75c3cd4c3d]
 - handle binder_update_page_range because of missing 720c241924046
 - handle mlx5_ib_disassociate_ucontext - akaher@vmware.com
]
Signed-off-by: Michal Hocko 
Signed-off-by: Greg Kroah-Hartman

configfs: Fix use-after-free when accessing sd->s_dentry

2019-06-22T06:18:26+00:00

[ Upstream commit f6122ed2a4f9c9c1c073ddf6308d1b2ac10e0781 ]

In the vfs_statx() context, during path lookup, the dentry gets
added to sd->s_dentry via configfs_attach_attr(). In the end,
vfs_statx() kills the dentry by calling path_put(), which invokes
configfs_d_iput(). Ideally, this dentry must be removed from
sd->s_dentry but it doesn't if the sd->s_count >= 3. As a result,
sd->s_dentry is holding reference to a stale dentry pointer whose
memory is already freed up. This results in use-after-free issue,
when this stale sd->s_dentry is accessed later in
configfs_readdir() path.

This issue can be easily reproduced, by running the LTP test case -
sh fs_racer_file_list.sh /config
(https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/fs/racer/fs_racer_file_list.sh)

Fixes: 76ae281f6307 ('configfs: fix race between dentry put and lookup')
Signed-off-by: Sahitya Tummala 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Sasha Levin

fs/ocfs2: fix race in ocfs2_dentry_attach_lock()

2019-06-22T06:18:22+00:00

commit be99ca2716972a712cde46092c54dee5e6192bf8 upstream.

ocfs2_dentry_attach_lock() can be executed in parallel threads against the
same dentry.  Make that race safe.  The race is like this:

            thread A                               thread B

(A1) enter ocfs2_dentry_attach_lock,
seeing dentry->d_fsdata is NULL,
and no alias found by
ocfs2_find_local_alias, so kmalloc
a new ocfs2_dentry_lock structure
to local variable "dl", dl1

               .....

                                    (B1) enter ocfs2_dentry_attach_lock,
                                    seeing dentry->d_fsdata is NULL,
                                    and no alias found by
                                    ocfs2_find_local_alias so kmalloc
                                    a new ocfs2_dentry_lock structure
                                    to local variable "dl", dl2.

                                                   ......

(A2) set dentry->d_fsdata with dl1,
call ocfs2_dentry_lock() and increase
dl1->dl_lockres.l_ro_holders to 1 on
success.
              ......

                                    (B2) set dentry->d_fsdata with dl2
                                    call ocfs2_dentry_lock() and increase
				    dl2->dl_lockres.l_ro_holders to 1 on
				    success.

                                                  ......

(A3) call ocfs2_dentry_unlock()
and decrease
dl2->dl_lockres.l_ro_holders to 0
on success.
             ....

                                    (B3) call ocfs2_dentry_unlock(),
                                    decreasing
				    dl2->dl_lockres.l_ro_holders, but
				    see it's zero now, panic

Link: http://lkml.kernel.org/r/20190529174636.22364-1-wen.gang.wang@oracle.com
Signed-off-by: Wengang Wang 
Reported-by: Daniel Sobe 
Tested-by: Daniel Sobe 
Reviewed-by: Changwei Ge 
Reviewed-by: Joseph Qi 
Cc: Mark Fasheh 
Cc: Joel Becker 
Cc: Junxiao Bi 
Cc: Gang He 
Cc: Jun Piao 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

nfsd: allow fh_want_write to be called twice

2019-06-22T06:18:20+00:00

[ Upstream commit 0b8f62625dc309651d0efcb6a6247c933acd8b45 ]

A fuzzer recently triggered lockdep warnings about potential sb_writers
deadlocks caused by fh_want_write().

Looks like we aren't careful to pair each fh_want_write() with an
fh_drop_write().

It's not normally a problem since fh_put() will call fh_drop_write() for
us.  And was OK for NFSv3 where we'd do one operation that might call
fh_want_write(), and then put the filehandle.

But an NFSv4 protocol fuzzer can do weird things like call unlink twice
in a compound, and then we get into trouble.

I'm a little worried about this approach of just leaving everything to
fh_put().  But I think there are probably a lot of
fh_want_write()/fh_drop_write() imbalances so for now I think we need it
to be more forgiving.

Signed-off-by: J. Bruce Fields 
Signed-off-by: Sasha Levin

fuse: retrieve: cap requested size to negotiated max_write

2019-06-22T06:18:20+00:00

[ Upstream commit 7640682e67b33cab8628729afec8ca92b851394f ]

FUSE filesystem server and kernel client negotiate during initialization
phase, what should be the maximum write size the client will ever issue.
Correspondingly the filesystem server then queues sys_read calls to read
requests with buffer capacity large enough to carry request header + that
max_write bytes. A filesystem server is free to set its max_write in
anywhere in the range between [1*page, fc->max_pages*page]. In particular
go-fuse[2] sets max_write by default as 64K, wheres default fc->max_pages
corresponds to 128K. Libfuse also allows users to configure max_write, but
by default presets it to possible maximum.

If max_write is < fc->max_pages*page, and in NOTIFY_RETRIEVE handler we
allow to retrieve more than max_write bytes, corresponding prepared
NOTIFY_REPLY will be thrown away by fuse_dev_do_read, because the
filesystem server, in full correspondence with server/client contract, will
be only queuing sys_read with ~max_write buffer capacity, and
fuse_dev_do_read throws away requests that cannot fit into server request
buffer. In turn the filesystem server could get stuck waiting indefinitely
for NOTIFY_REPLY since NOTIFY_RETRIEVE handler returned OK which is
understood by clients as that NOTIFY_REPLY was queued and will be sent
back.

Cap requested size to negotiate max_write to avoid the problem.  This
aligns with the way NOTIFY_RETRIEVE handler works, which already
unconditionally caps requested retrieve size to fuse_conn->max_pages.  This
way it should not hurt NOTIFY_RETRIEVE semantic if we return less data than
was originally requested.

Please see [1] for context where the problem of stuck filesystem was hit
for real, how the situation was traced and for more involving patch that
did not make it into the tree.

[1] https://marc.info/?l=linux-fsdevel&m=155057023600853&w=2
[2] https://github.com/hanwen/go-fuse

Signed-off-by: Kirill Smelkov 
Cc: Han-Wen Nienhuys 
Cc: Jakob Unterwurzacher 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Sasha Levin

f2fs: fix to do sanity check on valid block count of segment

2019-06-22T06:18:19+00:00

[ Upstream commit e95bcdb2fefa129f37bd9035af1d234ca92ee4ef ]

As Jungyeon reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=203233

- Overview
When mounting the attached crafted image and running program, following errors are reported.
Additionally, it hangs on sync after running program.

The image is intentionally fuzzed from a normal f2fs image for testing.
Compile options for F2FS are as follows.
CONFIG_F2FS_FS=y
CONFIG_F2FS_STAT_FS=y
CONFIG_F2FS_FS_XATTR=y
CONFIG_F2FS_FS_POSIX_ACL=y
CONFIG_F2FS_CHECK_FS=y

- Reproduces
cc poc_13.c
mkdir test
mount -t f2fs tmp.img test
cp a.out test
cd test
sudo ./a.out
sync

- Kernel messages
 F2FS-fs (sdb): Bitmap was wrongly set, blk:4608
 kernel BUG at fs/f2fs/segment.c:2102!
 RIP: 0010:update_sit_entry+0x394/0x410
 Call Trace:
  f2fs_allocate_data_block+0x16f/0x660
  do_write_page+0x62/0x170
  f2fs_do_write_node_page+0x33/0xa0
  __write_node_page+0x270/0x4e0
  f2fs_sync_node_pages+0x5df/0x670
  f2fs_write_checkpoint+0x372/0x1400
  f2fs_sync_fs+0xa3/0x130
  f2fs_do_sync_file+0x1a6/0x810
  do_fsync+0x33/0x60
  __x64_sys_fsync+0xb/0x10
  do_syscall_64+0x43/0xf0
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

sit.vblocks and sum valid block count in sit.valid_map may be
inconsistent, segment w/ zero vblocks will be treated as free
segment, while allocating in free segment, we may allocate a
free block, if its bitmap is valid previously, it can cause
kernel crash due to bitmap verification failure.

Anyway, to avoid further serious metadata inconsistence and
corruption, it is necessary and worth to detect SIT
inconsistence. So let's enable check_block_count() to verify
vblocks and valid_map all the time rather than do it only
CONFIG_F2FS_CHECK_FS is enabled.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim 
Signed-off-by: Sasha Levin

f2fs: fix to avoid panic in do_recover_data()

2019-06-22T06:18:19+00:00

[ Upstream commit 22d61e286e2d9097dae36f75ed48801056b77cac ]

As Jungyeon reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=203227

- Overview
When mounting the attached crafted image, following errors are reported.
Additionally, it hangs on sync after trying to mount it.

The image is intentionally fuzzed from a normal f2fs image for testing.
Compile options for F2FS are as follows.
CONFIG_F2FS_FS=y
CONFIG_F2FS_STAT_FS=y
CONFIG_F2FS_FS_XATTR=y
CONFIG_F2FS_FS_POSIX_ACL=y
CONFIG_F2FS_CHECK_FS=y

- Reproduces
mkdir test
mount -t f2fs tmp.img test
sync

- Messages
 kernel BUG at fs/f2fs/recovery.c:549!
 RIP: 0010:recover_data+0x167a/0x1780
 Call Trace:
  f2fs_recover_fsync_data+0x613/0x710
  f2fs_fill_super+0x1043/0x1aa0
  mount_bdev+0x16d/0x1a0
  mount_fs+0x4a/0x170
  vfs_kern_mount+0x5d/0x100
  do_mount+0x200/0xcf0
  ksys_mount+0x79/0xc0
  __x64_sys_mount+0x1c/0x20
  do_syscall_64+0x43/0xf0
  entry_SYSCALL_64_after_hwframe+0x44/0xa9

During recovery, if ofs_of_node is inconsistent in between recovered
node page and original checkpointed node page, let's just fail recovery
instead of making kernel panic.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim 
Signed-off-by: Sasha Levin

fs/fat/file.c: issue flush after the writeback of FAT

2019-06-22T06:18:17+00:00

[ Upstream commit bd8309de0d60838eef6fb575b0c4c7e95841cf73 ]

fsync() needs to make sure the data & meta-data of file are persistent
after the return of fsync(), even when a power-failure occurs later.  In
the case of fat-fs, the FAT belongs to the meta-data of file, so we need
to issue a flush after the writeback of FAT instead before.

Also bail out early when any stage of fsync fails.

Link: http://lkml.kernel.org/r/20190409030158.136316-1-houtao1@huawei.com
Signed-off-by: Hou Tao 
Acked-by: OGAWA Hirofumi 
Cc: Al Viro 
Cc: Jan Kara 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

fuse: Add FOPEN_STREAM to use stream_open()

2019-06-11T10:24:13+00:00

commit bbd84f33652f852ce5992d65db4d020aba21f882 upstream.

Starting from commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per
POSIX") files opened even via nonseekable_open gate read and write via lock
and do not allow them to be run simultaneously. This can create read vs
write deadlock if a filesystem is trying to implement a socket-like file
which is intended to be simultaneously used for both read and write from
filesystem client.  See commit 10dce8af3422 ("fs: stream_open - opener for
stream-like files so that read and write can run simultaneously without
deadlock") for details and e.g. commit 581d21a2d02a ("xenbus: fix deadlock
on writes to /proc/xen/xenbus") for a similar deadlock example on
/proc/xen/xenbus.

To avoid such deadlock it was tempting to adjust fuse_finish_open to use
stream_open instead of nonseekable_open on just FOPEN_NONSEEKABLE flags,
but grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE,
and in particular GVFS which actually uses offset in its read and write
handlers

	https://codesearch.debian.net/search?q=-%3Enonseekable+%3D
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481

so if we would do such a change it will break a real user.

Add another flag (FOPEN_STREAM) for filesystem servers to indicate that the
opened handler is having stream-like semantics; does not use file position
and thus the kernel is free to issue simultaneous read and write request on
opened file handle.

This patch together with stream_open() should be added to stable kernels
starting from v3.14+. This will allow to patch OSSPD and other FUSE
filesystems that provide stream-like files to return FOPEN_STREAM |
FOPEN_NONSEEKABLE in open handler and this way avoid the deadlock on all
kernel versions. This should work because fuse_finish_open ignores unknown
open flags returned from a filesystem and so passing FOPEN_STREAM to a
kernel that is not aware of this flag cannot hurt. In turn the kernel that
is not aware of FOPEN_STREAM will be < v3.14 where just FOPEN_NONSEEKABLE
is sufficient to implement streams without read vs write deadlock.

Cc: stable@vger.kernel.org # v3.14+
Signed-off-by: Kirill Smelkov 
Signed-off-by: Miklos Szeredi 
Signed-off-by: Greg Kroah-Hartman