code is actually simpler that way.
Acked-by: "Tigran A. Aivazian" <aivazian.tigran@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

kill_ioctx() used to have an explicit RCU delay between removing the
reference from ->ioctx_table and percpu_ref_kill() dropping the refcount.
At some point that delay had been removed, on the theory that
percpu_ref_kill() itself contained an RCU delay.  Unfortunately, that was
the wrong kind of RCU delay and it didn't care about rcu_read_lock() used
by lookup_ioctx().  As the result, we could get ctx freed right under
lookup_ioctx().  Tejun has fixed that in a6d7cff4 ("fs/aio: Add explicit
RCU grace period when freeing kioctx"); however, that fix is not enough.

Suppose io_destroy() from one thread races with e.g. io_setup() from another;
CPU1 removes the reference from current->mm->ioctx_table[...] just as CPU2
has picked it (under rcu_read_lock()).  Then CPU1 proceeds to drop the
refcount, getting it to 0 and triggering a call of free_ioctx_users(),
which proceeds to drop the secondary refcount and once that reaches zero
calls free_ioctx_reqs().  That does
        INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
        queue_rcu_work(system_wq, &ctx->free_rwork);
and schedules freeing the whole thing after RCU delay.

In the meanwhile CPU2 has gotten around to percpu_ref_get(), bumping the
refcount from 0 to 1 and returned the reference to io_setup().

Tejun's fix (that queue_rcu_work() in there) guarantees that ctx won't get
freed until after percpu_ref_get().  Sure, we'd increment the counter before
ctx can be freed.  Now we are out of rcu_read_lock() and there's nothing to
stop freeing of the whole thing.  Unfortunately, CPU2 assumes that since it
has grabbed the reference, ctx is *NOT* going away until it gets around to
dropping that reference.

The fix is obvious - use percpu_ref_tryget_live() and treat failure as miss.
It's not costlier than what we currently do in normal case, it's safe to
call since freeing *is* delayed and it closes the race window - either
lookup_ioctx() comes before percpu_ref_kill() (in which case ctx->users
won't reach 0 until the caller of lookup_ioctx() drops it) or lookup_ioctx()
fails, ctx->users is unaffected and caller of lookup_ioctx() doesn't see
the object in question at all.

Cc: stable@kernel.org
Fixes: a6d7cff4 "fs/aio: Add explicit RCU grace period when freeing kioctx"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

open file, unlink it, then use ioctl(2) to make it immutable or
append only.  Now close it and watch the blocks *not* freed...

Immutable/append-only checks belong in ->setattr().
Note: the bug is old and backport to anything prior to 737f2e93
("ext2: convert to use the new truncate convention") will need
these checks lifted into ext2_setattr().

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...
Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

That can (and does, on some filesystems) happen - ->mkdir() (and thus
vfs_mkdir()) can legitimately leave its argument negative and just
unhash it, counting upon the lookup to pick the object we'd created
next time we try to look at that name.

Some vfs_mkdir() callers forget about that possibility...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

new_sb is left uninitialized in case of early failures in kernfs_mount_ns(),
and while IS_ERR(root) is true in all such cases, using IS_ERR(root) || !new_sb
is not a solution - IS_ERR(root) is true in some cases when new_sb is true.

Make sure new_sb is initialized (and matches the reality) in all cases and
fix the condition for dropping kobj reference - we want it done precisely
in those situations where the reference has not been transferred into a new
super_block instance.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

make sure that info->node is initialized early, so that kernfs_kill_sb()
can list_del() it safely.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

There's an extra C here...

Fixes: 99c18ce5 ("cramfs: direct memory access support")
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

RTFS(Documentation/filesystems/nfs/Exporting) if you try to make
something exportable.

Fixes: ac632f5b "befs: add NFS export support"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Making something exportable takes more than providing ->s_export_ops.
In particular, ->lookup() *MUST* use d_splice_alias() instead of
d_add().

Reading Documentation/filesystems/nfs/Exporting would've been a good idea;
as it is, exporting AFFS is badly (and exploitably) broken.

Partially-Fixes: ed4433d7 "fs/affs: make affs exportable"
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

we unlock the directory hash too early - if we are looking at secondary
link and primary (in another directory) gets removed just as we unlock,
we could have the old primary moved in place of the secondary, leaving
us to look into freed entry (and leaving our dentry with ->d_fsdata
pointing to a freed entry).

Cc: stable@vger.kernel.org # 2.4.4+
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Use path_equal() to detect whether we're already in root.
Signed-off-by: Danilo Krummrich <danilokrummrich@dk-develop.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

The __dentry_open function was removed in
commit <2a027e7a>("fold __dentry_open() into its sole caller").
Signed-off-by: Li Qiang <liq3ea@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

many years overdue...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

"VFS: don't keep disconnected dentries on d_anon" had a non-trivial
side-effect - d_unhashed() now returns true for those dentries,
making d_find_alias() skip them altogether.  For most of its callers
that's fine - we really want a connected alias there.  However,
there is a codepath where we relied upon picking such aliases
if nothing else could be found - selinux delayed initialization
of contexts for inodes on already mounted filesystems used to
rely upon that.

Cc: stable@kernel.org # f1ee6162 "VFS: don't keep disconnected dentries on d_anon"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfat_d_anon_disconn() is called only if alias->d_parent is equal to
dentry->d_parent *and* it returns false unless alias->d_parent == alias.
But in that case alias is the directory we are doing lookup in, and
d_splice_alias() would've done the right thing.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

All "try disconnected alias if nothing else fits" logics in d_find_alias()
got accidentally disabled by Neil a while ago; for most of the callers it
was the right thing to do, so fixes belong in few callers that *do* want
disconnected aliases.  This just takes the now-dead code in d_find_alias()
out.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

We recently had an oops reported on a 4.14 kernel in
xfs_reclaim_inodes_count() where sb->s_fs_info pointed to garbage
and so the m_perag_tree lookup walked into lala land.  It produces
an oops down this path during the failed mount:

  radix_tree_gang_lookup_tag+0xc4/0x130
  xfs_perag_get_tag+0x37/0xf0
  xfs_reclaim_inodes_count+0x32/0x40
  xfs_fs_nr_cached_objects+0x11/0x20
  super_cache_count+0x35/0xc0
  shrink_slab.part.66+0xb1/0x370
  shrink_node+0x7e/0x1a0
  try_to_free_pages+0x199/0x470
  __alloc_pages_slowpath+0x3a1/0xd20
  __alloc_pages_nodemask+0x1c3/0x200
  cache_grow_begin+0x20b/0x2e0
  fallback_alloc+0x160/0x200
  kmem_cache_alloc+0x111/0x4e0

The problem is that the superblock shrinker is running before the
filesystem structures it depends on have been fully set up. i.e.
the shrinker is registered in sget(), before ->fill_super() has been
called, and the shrinker can call into the filesystem before
fill_super() does it's setup work. Essentially we are exposed to
both use-after-free and use-before-initialisation bugs here.

To fix this, add a check for the SB_BORN flag in super_cache_count.
In general, this flag is not set until ->fs_mount() completes
successfully, so we know that it is set after the filesystem
setup has completed. This matches the trylock_super() behaviour
which will not let super_cache_scan() run if SB_BORN is not set, and
hence will not allow the superblock shrinker from entering the
filesystem while it is being set up or after it has failed setup
and is being torn down.

Cc: stable@kernel.org
Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
	lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
->i_mutex.  Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.

	Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode().  All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.

Cc: stable@kernel.org	# 2.6.29 and later
Tested-by: Mike Marshall <hubcap@omnibond.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Make n signed to avoid leaking the pages array if __pipe_get_pages()
fails to allocate any pages.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

It returns -EFAULT and happens to be a helper for pipe_get_pages()
whose return type is ssize_t.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

it hadn't been checking for "busy" since 2.3.99-something and removing
that leaves us with "check if it's empty" followed by call of fat_dir_emtpy()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

We want it only for the stuff created by SB_KERNMOUNT mounts, *not* for
their copies.  As it is, creating a deep stack of bindings of /proc/*/ns/*
somewhere in a new namespace and exiting yields a stack overflow.

Cc: stable@kernel.org
Reported-by: Alexander Aring <aring@mojatatu.com>
Bisected-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Tested-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Tested-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

no users since 2014...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

syzbot is catching so many bugs triggered by commit 9ee332d9
("sget(): handle failures of register_shrinker()"). That commit expected
that calling kill_sb() from deactivate_locked_super() without successful
fill_super() is safe, but the reality was different; some callers assign
attributes which are needed for kill_sb() after sget() succeeds.

For example, [1] is a report where sb->s_mode (which seems to be either
FMODE_READ | FMODE_EXCL | FMODE_WRITE or FMODE_READ | FMODE_EXCL) is not
assigned unless sget() succeeds. But it does not worth complicate sget()
so that register_shrinker() failure path can safely call
kill_block_super() via kill_sb(). Making alloc_super() fail if memory
allocation for register_shrinker() failed is much simpler. Let's avoid
calling deactivate_locked_super() from sget_userns() by preallocating
memory for the shrinker and making register_shrinker() in sget_userns()
never fail.

[1] https://syzkaller.appspot.com/bug?id=588996a25a2587be2e3a54e8646728fb9cae44e7Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+5a170e19c963a2e0df79@syzkaller.appspotmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

if we ever hit rpc_gssd_dummy_depopulate() dentry passed to
it has refcount equal to 1.  __rpc_rmpipe() drops it and
dput() done after that hits an already freed dentry.

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

orangefs_fill_sb() might've failed to allocate ORANGEFS_SB(s); don't
oops in that case.

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

jffs2_fill_super() might fail to allocate jffs2_sb_info;
jffs2_kill_sb() must survive that.

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

hypfs_fill_super() might fail to allocate sbi; hypfs_kill_super()
should not oops on that.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

It's a fairly inconsequential bug, since fdput() won't actually try to
fput() the file due to fd.flags (and thus FDPUT_FPUT) being zero in
the failure case, but most other vfs code takes steps to avoid this.
Signed-off-by: Zev Weiss <zev@bewilderbeest.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull more btrfs updates from David Sterba:
 "We have queued a few more fixes (error handling, log replay,
  softlockup) and the rest is SPDX updates that touche almost all files
  so the diffstat is long"

* tag 'for-4.17-part2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: Only check first key for committed tree blocks
  btrfs: add SPDX header to Kconfig
  btrfs: replace GPL boilerplate by SPDX -- sources
  btrfs: replace GPL boilerplate by SPDX -- headers
  Btrfs: fix loss of prealloc extents past i_size after fsync log replay
  Btrfs: clean up resources during umount after trans is aborted
  btrfs: Fix possible softlock on single core machines
  Btrfs: bail out on error during replay_dir_deletes
  Btrfs: fix NULL pointer dereference in log_dir_items

Pull cifs fixes from Steve French:
 "SMB3 fixes, a few for stable, and some important cleanup work from
  Ronnie of the smb3 transport code"

* tag '4.17-rc1SMB3-Fixes' of git://git.samba.org/sfrench/cifs-2.6:
  cifs: change validate_buf to validate_iov
  cifs: remove rfc1002 hardcoded constants from cifs_discard_remaining_data()
  cifs: Change SMB2_open to return an iov for the error parameter
  cifs: add resp_buf_size to the mid_q_entry structure
  smb3.11: replace a 4 with server->vals->header_preamble_size
  cifs: replace a 4 with server->vals->header_preamble_size
  cifs: add pdu_size to the TCP_Server_Info structure
  SMB311: Improve checking of negotiate security contexts
  SMB3: Fix length checking of SMB3.11 negotiate request
  CIFS: add ONCE flag for cifs_dbg type
  cifs: Use ULL suffix for 64-bit constant
  SMB3: Log at least once if tree connect fails during reconnect
  cifs: smb2pdu: Fix potential NULL pointer dereference

Pull SCSI fixes from James Bottomley:
 "This is a set of minor (and safe changes) that didn't make the initial
  pull request plus some bug fixes.

  The status handling code is actually a running regression from the
  previous merge window which had an incomplete fix (now reverted) and
  most of the remaining bug fixes are for problems older than the
  current merge window"

[ Side note: this merge also takes the base kernel git repository to 6+
  million objects for the first time. Technically we hit it a couple of
  merges ago already if you count all the tag objects, but now it
  reaches 6M+ objects reachable from HEAD.

  I was joking around that that's when I should switch to 5.0, because
  3.0 happened at the 2M mark, and 4.0 happened at 4M objects. But
  probably not, even if numerology is about as good a reason as any.

                                                              - Linus ]

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: devinfo: Add Microsoft iSCSI target to 1024 sector blacklist
  scsi: cxgb4i: silence overflow warning in t4_uld_rx_handler()
  scsi: dpt_i2o: Use after free in I2ORESETCMD ioctl
  scsi: core: Make scsi_result_to_blk_status() recognize CONDITION MET
  scsi: core: Rename __scsi_error_from_host_byte() into scsi_result_to_blk_status()
  Revert "scsi: core: return BLK_STS_OK for DID_OK in __scsi_error_from_host_byte()"
  scsi: aacraid: Insure command thread is not recursively stopped
  scsi: qla2xxx: Correct setting of SAM_STAT_CHECK_CONDITION
  scsi: qla2xxx: correctly shift host byte
  scsi: qla2xxx: Fix race condition between iocb timeout and initialisation
  scsi: qla2xxx: Avoid double completion of abort command
  scsi: qla2xxx: Fix small memory leak in qla2x00_probe_one on probe failure
  scsi: scsi_dh: Don't look for NULL devices handlers by name
  scsi: core: remove redundant assignment to shost->use_blk_mq

Pull more Kbuild updates from Masahiro Yamada:

 - pass HOSTLDFLAGS when compiling single .c host programs

 - build genksyms lexer and parser files instead of using shipped
   versions

 - rename *-asn1.[ch] to *.asn1.[ch] for suffix consistency

 - let the top .gitignore globally ignore artifacts generated by flex,
   bison, and asn1_compiler

 - let the top Makefile globally clean artifacts generated by flex,
   bison, and asn1_compiler

 - use safer .SECONDARY marker instead of .PRECIOUS to prevent
   intermediate files from being removed

 - support -fmacro-prefix-map option to make __FILE__ a relative path

 - fix # escaping to prepare for the future GNU Make release

 - clean up deb-pkg by using debian tools instead of handrolled
   source/changes generation

 - improve rpm-pkg portability by supporting kernel-install as a
   fallback of new-kernel-pkg

 - extend Kconfig listnewconfig target to provide more information

* tag 'kbuild-v4.17-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: extend output of 'listnewconfig'
  kbuild: rpm-pkg: use kernel-install as a fallback for new-kernel-pkg
  Kbuild: fix # escaping in .cmd files for future Make
  kbuild: deb-pkg: split generating packaging and build
  kbuild: use -fmacro-prefix-map to make __FILE__ a relative path
  kbuild: mark $(targets) as .SECONDARY and remove .PRECIOUS markers
  kbuild: rename *-asn1.[ch] to *.asn1.[ch]
  kbuild: clean up *-asn1.[ch] patterns from top-level Makefile
  .gitignore: move *-asn1.[ch] patterns to the top-level .gitignore
  kbuild: add %.dtb.S and %.dtb to 'targets' automatically
  kbuild: add %.lex.c and %.tab.[ch] to 'targets' automatically
  genksyms: generate lexer and parser during build instead of shipping
  kbuild: clean up *.lex.c and *.tab.[ch] patterns from top-level Makefile
  .gitignore: move *.lex.c *.tab.[ch] patterns to the top-level .gitignore
  kbuild: use HOSTLDFLAGS for single .c executables

Pull x86 fixes from Thomas Gleixner:
 "A set of fixes and updates for x86:

   - Address a swiotlb regression which was caused by the recent DMA
     rework and made driver fail because dma_direct_supported() returned
     false

   - Fix a signedness bug in the APIC ID validation which caused invalid
     APIC IDs to be detected as valid thereby bloating the CPU possible
     space.

   - Fix inconsisten config dependcy/select magic for the MFD_CS5535
     driver.

   - Fix a corruption of the physical address space bits when encryption
     has reduced the address space and late cpuinfo updates overwrite
     the reduced bit information with the original value.

   - Dominiks syscall rework which consolidates the architecture
     specific syscall functions so all syscalls can be wrapped with the
     same macros. This allows to switch x86/64 to struct pt_regs based
     syscalls. Extend the clearing of user space controlled registers in
     the entry patch to the lower registers"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/apic: Fix signedness bug in APIC ID validity checks
  x86/cpu: Prevent cpuinfo_x86::x86_phys_bits adjustment corruption
  x86/olpc: Fix inconsistent MFD_CS5535 configuration
  swiotlb: Use dma_direct_supported() for swiotlb_ops
  syscalls/x86: Adapt syscall_wrapper.h to the new syscall stub naming convention
  syscalls/core, syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()
  syscalls/core, syscalls/x86: Clean up compat syscall stub naming convention
  syscalls/core, syscalls/x86: Clean up syscall stub naming convention
  syscalls/x86: Extend register clearing on syscall entry to lower registers
  syscalls/x86: Unconditionally enable 'struct pt_regs' based syscalls on x86_64
  syscalls/x86: Use 'struct pt_regs' based syscall calling for IA32_EMULATION and x32
  syscalls/core: Prepare CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y for compat syscalls
  syscalls/x86: Use 'struct pt_regs' based syscall calling convention for 64-bit syscalls
  syscalls/core: Introduce CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y
  x86/syscalls: Don't pointlessly reload the system call number
  x86/mm: Fix documentation of module mapping range with 4-level paging
  x86/cpuid: Switch to 'static const' specifier

Pull x86 pti updates from Thomas Gleixner:
 "Another series of PTI related changes:

   - Remove the manual stack switch for user entries from the idtentry
     code. This debloats entry by 5k+ bytes of text.

   - Use the proper types for the asm/bootparam.h defines to prevent
     user space compile errors.

   - Use PAGE_GLOBAL for !PCID systems to gain back performance

   - Prevent setting of huge PUD/PMD entries when the entries are not
     leaf entries otherwise the entries to which the PUD/PMD points to
     and are populated get lost"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/pgtable: Don't set huge PUD/PMD on non-leaf entries
  x86/pti: Leave kernel text global for !PCID
  x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image
  x86/pti: Enable global pages for shared areas
  x86/mm: Do not forbid _PAGE_RW before init for __ro_after_init
  x86/mm: Comment _PAGE_GLOBAL mystery
  x86/mm: Remove extra filtering in pageattr code
  x86/mm: Do not auto-massage page protections
  x86/espfix: Document use of _PAGE_GLOBAL
  x86/mm: Introduce "default" kernel PTE mask
  x86/mm: Undo double _PAGE_PSE clearing
  x86/mm: Factor out pageattr _PAGE_GLOBAL setting
  x86/entry/64: Drop idtentry's manual stack switch for user entries
  x86/uapi: Fix asm/bootparam.h userspace compilation errors