Pull driver core and debugfs fixes from Greg KH:
 "Here are four small driver core / debugfs patches for 5.6-rc3:

   - debugfs api cleanup now that all debugfs_create_regset32() callers
     have been fixed up. This was waiting until after the -rc1 merge as
     these fixes came in through different trees

   - driver core sync state fixes based on reports of minor issues found
     in the feature

  All of these have been in linux-next with no reported issues"

* tag 'driver-core-5.6-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  driver core: Skip unnecessary work when device doesn't have sync_state()
  driver core: Add dev_has_sync_state()
  driver core: Call sync_state() even if supplier has no consumers
  debugfs: remove return value of debugfs_create_regset32()

Pull io_uring fixes from Jens Axboe:
 "Here are a few io_uring fixes that should go into this release. This
  contains:

   - Removal of (now) unused io_wq_flush() and associated flag (Pavel)

   - Fix cancelation lockup with linked timeouts (Pavel)

   - Fix for potential use-after-free when freeing percpu ref for fixed
     file sets

   - io-wq cancelation fixups (Pavel)"

* tag 'io_uring-5.6-2020-03-07' of git://git.kernel.dk/linux-block:
  io_uring: fix lockup with timeouts
  io_uring: free fixed_file_data after RCU grace period
  io-wq: remove io_wq_flush and IO_WQ_WORK_INTERNAL
  io-wq: fix IO_WQ_WORK_NO_CANCEL cancellation

There is a recipe to deadlock the kernel: submit a timeout sqe with a
linked_timeout (e.g.  test_single_link_timeout_ception() from liburing),
and SIGKILL the process.

Then, io_kill_timeouts() takes @ctx->completion_lock, but the timeout
isn't flagged with REQ_F_COMP_LOCKED, and will try to double grab it
during io_put_free() to cancel the linked timeout. Probably, the same
can happen with another io_kill_timeout() call site, that is
io_commit_cqring().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull btrfs fix from David Sterba:
 "One fixup for DIO when in use with the new checksums, a missed case
  where the checksum size was still assuming u32"

* tag 'for-5.6-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: fix RAID direct I/O reads with alternate csums

Pull file locking fixes from Jeff Layton:
 "Just a couple of late-breaking patches for the file locking code. The
  second patch (from yangerkun) fixes a rather nasty looking potential
  use-after-free that should go to stable.

  The other patch could technically wait for 5.7, but it's fairly
  innocuous so I figured we might as well take it"

* tag 'filelock-v5.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  locks: fix a potential use-after-free problem when wakeup a waiter
  fcntl: Distribute switch variables for initialization

The percpu refcount protects this structure, and we can have an atomic
switch in progress when exiting. This makes it unsafe to just free the
struct normally, and can trigger the following KASAN warning:

BUG: KASAN: use-after-free in percpu_ref_switch_to_atomic_rcu+0xfa/0x1b0
Read of size 1 at addr ffff888181a19a30 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc4+ #5747
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
Call Trace:
 <IRQ>
 dump_stack+0x76/0xa0
 print_address_description.constprop.0+0x3b/0x60
 ? percpu_ref_switch_to_atomic_rcu+0xfa/0x1b0
 ? percpu_ref_switch_to_atomic_rcu+0xfa/0x1b0
 __kasan_report.cold+0x1a/0x3d
 ? percpu_ref_switch_to_atomic_rcu+0xfa/0x1b0
 percpu_ref_switch_to_atomic_rcu+0xfa/0x1b0
 rcu_core+0x370/0x830
 ? percpu_ref_exit+0x50/0x50
 ? rcu_note_context_switch+0x7b0/0x7b0
 ? run_rebalance_domains+0x11d/0x140
 __do_softirq+0x10a/0x3e9
 irq_exit+0xd5/0xe0
 smp_apic_timer_interrupt+0x86/0x200
 apic_timer_interrupt+0xf/0x20
 </IRQ>
RIP: 0010:default_idle+0x26/0x1f0

Fix this by punting the final exit and free of the struct to RCU, then
we know that it's safe to do so. Jann suggested the approach of using a
double rcu callback to achieve this. It's important that we do a nested
call_rcu() callback, as otherwise the free could be ordered before the
atomic switch, even if the latter was already queued.

Reported-by: syzbot+e017e49c39ab484ac87a@syzkaller.appspotmail.com
Suggested-by: Jann Horn <jannh@google.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

'16306a61d3b7 ("fs/locks: always delete_block after waiting.")' add the
logic to check waiter->fl_blocker without blocked_lock_lock. And it will
trigger a UAF when we try to wakeup some waiter：

Thread 1 has create a write flock a on file, and now thread 2 try to
unlock and delete flock a, thread 3 try to add flock b on the same file.

Thread2                         Thread3
                                flock syscall(create flock b)
	                        ...flock_lock_inode_wait
				    flock_lock_inode(will insert
				    our fl_blocked_member list
				    to flock a's fl_blocked_requests)
				   sleep
flock syscall(unlock)
...flock_lock_inode_wait
    locks_delete_lock_ctx
    ...__locks_wake_up_blocks
        __locks_delete_blocks(
	b->fl_blocker = NULL)
	...
                                   break by a signal
				   locks_delete_block
				    b->fl_blocker == NULL &&
				    list_empty(&b->fl_blocked_requests)
	                            success, return directly
				 locks_free_lock b
	wake_up(&b->fl_waiter)
	trigger UAF

Fix it by remove this logic, and this patch may also fix CVE-2019-19769.

Cc: stable@vger.kernel.org
Fixes: 16306a61d3b7 ("fs/locks: always delete_block after waiting.")
Signed-off-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>

When get an error in the middle of reading an inode, some fields in the
inode might be still not initialized.  And then the evict_inode path may
access those fields via iput().

To fix, this makes sure that inode fields are initialized.

Reported-by: syzbot+9d82b8de2992579da5d0@syzkaller.appspotmail.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/871rqnreqx.fsf@mail.parknet.co.jp
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull cifs fixes from Steve French:
 "Five small cifs/smb3 fixes, two for stable (one for a reconnect
  problem and the other fixes a use case when renaming an open file)"

* tag '5.6-rc4-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: Use #define in cifs_dbg
  cifs: fix rename() by ensuring source handle opened with DELETE bit
  cifs: add missing mount option to /proc/mounts
  cifs: fix potential mismatch of UNC paths
  cifs: don't leak -EAGAIN for stat() during reconnect

Variables declared in a switch statement before any case statements
cannot be automatically initialized with compiler instrumentation (as
they are not part of any execution flow). With GCC's proposed automatic
stack variable initialization feature, this triggers a warning (and they
don't get initialized). Clang's automatic stack variable initialization
(via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also
doesn't initialize such variables[1]. Note that these warnings (or silent
skipping) happen before the dead-store elimination optimization phase,
so even when the automatic initializations are later elided in favor of
direct initializations, the warnings remain.

To avoid these problems, move such variables into the "case" where
they're used or lift them up into the main function body.

fs/fcntl.c: In function ‘send_sigio_to_task’:
fs/fcntl.c:738:20: warning: statement will never be executed [-Wswitch-unreachable]
  738 |   kernel_siginfo_t si;
      |                    ^~

[1] https://bugs.llvm.org/show_bug.cgi?id=44916

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jeff Layton <jlayton@kernel.org>