linux.git/fs/aio.c, branch v5.17

aio: move aio sysctl to aio.c

2022-01-22T06:33:34+00:00

The kernel/sysctl.c is a kitchen sink where everyone leaves their dirty
dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to places
where they actually belong.  The proc sysctl maintainers do not want to
know what sysctl knobs you wish to add for your own piece of code, we
just care about the core logic.

Move aio sysctl to aio.c and use the new register_sysctl_init() to
register the sysctl interface for aio.

[mcgrof@kernel.org: adjust commit log to justify the move]

Link: https://lkml.kernel.org/r/20211123202347.818157-9-mcgrof@kernel.org
Signed-off-by: Xiaoming Ni 
Signed-off-by: Luis Chamberlain 
Reviewed-by: Jan Kara 
Cc: Al Viro 
Cc: Amir Goldstein 
Cc: Andy Shevchenko 
Cc: Benjamin LaHaise 
Cc: "Eric W. Biederman" 
Cc: Greg Kroah-Hartman 
Cc: Iurii Zaikin 
Cc: Kees Cook 
Cc: Paul Turner 
Cc: Peter Zijlstra 
Cc: Petr Mladek 
Cc: Qing Wang 
Cc: Sebastian Reichel 
Cc: Sergey Senozhatsky 
Cc: Stephen Kitt 
Cc: Tetsuo Handa 
Cc: Antti Palosaari 
Cc: Arnd Bergmann 
Cc: Benjamin Herrenschmidt 
Cc: Clemens Ladisch 
Cc: David Airlie 
Cc: Jani Nikula 
Cc: Joel Becker 
Cc: Joonas Lahtinen 
Cc: Joseph Qi 
Cc: Julia Lawall 
Cc: Lukas Middendorf 
Cc: Mark Fasheh 
Cc: Phillip Potter 
Cc: Rodrigo Vivi 
Cc: Douglas Gilbert 
Cc: James E.J. Bottomley 
Cc: Jani Nikula 
Cc: John Ogness 
Cc: Martin K. Petersen 
Cc: "Rafael J. Wysocki" 
Cc: Steven Rostedt (VMware) 
Cc: Suren Baghdasaryan 
Cc: "Theodore Ts'o" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

aio: Fix incorrect usage of eventfd_signal_allowed()

2021-12-09T18:52:55+00:00

We should defer eventfd_signal() to the workqueue when
eventfd_signal_allowed() return false rather than return
true.

Fixes: b542e383d8c0 ("eventfd: Make signal recursion protection a task bit")
Signed-off-by: Xie Yongji 
Link: https://lore.kernel.org/r/20210913111928.98-1-xieyongji@bytedance.com
Reviewed-by: Eric Biggers 
Signed-off-by: Eric Biggers

aio: fix use-after-free due to missing POLLFREE handling

2021-12-09T18:49:56+00:00

signalfd_poll() and binder_poll() are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case.  This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution.  This solution is for the queue to be cleared
before it is freed, by sending a POLLFREE notification to all waiters.

Unfortunately, only eventpoll handles POLLFREE.  A second type of
non-blocking poll, aio poll, was added in kernel v4.18, and it doesn't
handle POLLFREE.  This allows a use-after-free to occur if a signalfd or
binder fd is polled with aio poll, and the waitqueue gets freed.

Fix this by making aio poll handle POLLFREE.

A patch by Ramji Jiyani 
(https://lore.kernel.org/r/20211027011834.2497484-1-ramjiyani@google.com)
tried to do this by making aio_poll_wake() always complete the request
inline if POLLFREE is seen.  However, that solution had two bugs.
First, it introduced a deadlock, as it unconditionally locked the aio
context while holding the waitqueue lock, which inverts the normal
locking order.  Second, it didn't consider that POLLFREE notifications
are missed while the request has been temporarily de-queued.

The second problem was solved by my previous patch.  This patch then
properly fixes the use-after-free by handling POLLFREE in a
deadlock-free way.  It does this by taking advantage of the fact that
freeing of the waitqueue is RCU-delayed, similar to what eventpoll does.

Fixes: 2c14fa838cbe ("aio: implement IOCB_CMD_POLL")
Cc:  # v4.18+
Link: https://lore.kernel.org/r/20211209010455.42744-6-ebiggers@kernel.org
Signed-off-by: Eric Biggers

aio: keep poll requests on waitqueue until completed

2021-12-09T18:49:56+00:00

Currently, aio_poll_wake() will always remove the poll request from the
waitqueue.  Then, if aio_poll_complete_work() sees that none of the
polled events are ready and the request isn't cancelled, it re-adds the
request to the waitqueue.  (This can easily happen when polling a file
that doesn't pass an event mask when waking up its waitqueue.)

This is fundamentally broken for two reasons:

  1. If a wakeup occurs between vfs_poll() and the request being
     re-added to the waitqueue, it will be missed because the request
     wasn't on the waitqueue at the time.  Therefore, IOCB_CMD_POLL
     might never complete even if the polled file is ready.

  2. When the request isn't on the waitqueue, there is no way to be
     notified that the waitqueue is being freed (which happens when its
     lifetime is shorter than the struct file's).  This is supposed to
     happen via the waitqueue entries being woken up with POLLFREE.

Therefore, leave the requests on the waitqueue until they are actually
completed (or cancelled).  To keep track of when aio_poll_complete_work
needs to be scheduled, use new fields in struct poll_iocb.  Remove the
'done' field which is now redundant.

Note that this is consistent with how sys_poll() and eventpoll work;
their wakeup functions do *not* remove the waitqueue entries.

Fixes: 2c14fa838cbe ("aio: implement IOCB_CMD_POLL")
Cc:  # v4.18+
Link: https://lore.kernel.org/r/20211209010455.42744-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers

Merge tag 'kspp-misc-fixes-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux

2021-11-02T00:29:10+00:00

Pull hardening fixes and cleanups from Gustavo A. R. Silva:
 "Various hardening fixes and cleanups that I've been collecting during
  the last development cycle:

  Fix -Wcast-function-type error:

   - firewire: Remove function callback casts (Oscar Carter)

  Fix application of sizeof operator:

   - firmware/psci: fix application of sizeof to pointer (jing yangyang)

  Replace open coded instances with size_t saturating arithmetic
  helpers:

   - assoc_array: Avoid open coded arithmetic in allocator arguments
     (Len Baker)

   - writeback: prefer struct_size over open coded arithmetic (Len
     Baker)

   - aio: Prefer struct_size over open coded arithmetic (Len Baker)

   - dmaengine: pxa_dma: Prefer struct_size over open coded arithmetic
     (Len Baker)

  Flexible array transformation:

   - KVM: PPC: Replace zero-length array with flexible array member (Len
     Baker)

  Use 2-factor argument multiplication form:

   - nouveau/svm: Use kvcalloc() instead of kvzalloc() (Gustavo A. R.
     Silva)

   - xfs: Use kvcalloc() instead of kvzalloc() (Gustavo A. R. Silva)"

* tag 'kspp-misc-fixes-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux:
  firewire: Remove function callback casts
  nouveau/svm: Use kvcalloc() instead of kvzalloc()
  firmware/psci: fix application of sizeof to pointer
  dmaengine: pxa_dma: Prefer struct_size over open coded arithmetic
  KVM: PPC: Replace zero-length array with flexible array member
  aio: Prefer struct_size over open coded arithmetic
  writeback: prefer struct_size over open coded arithmetic
  xfs: Use kvcalloc() instead of kvzalloc()
  assoc_array: Avoid open coded arithmetic in allocator arguments

fs: get rid of the res2 iocb->ki_complete argument

2021-10-25T16:36:24+00:00

The second argument was only used by the USB gadget code, yet everyone
pays the overhead of passing a zero to be passed into aio, where it
ends up being part of the aio res2 value.

Now that everybody is passing in zero, kill off the extra argument.

Reviewed-by: Darrick J. Wong 
Signed-off-by: Jens Axboe

aio: Prefer struct_size over open coded arithmetic

2021-10-20T23:24:31+00:00

As noted in the "Deprecated Interfaces, Language Features, Attributes,
and Conventions" documentation [1], size calculations (especially
multiplication) should not be performed in memory allocator (or similar)
function arguments due to the risk of them overflowing. This could lead
to values wrapping around and a smaller allocation being made than the
caller was expecting. Using those allocations could lead to linear
overflows of heap memory and other misbehaviors.

So, use the struct_size() helper to do the arithmetic instead of the
argument "size + size * count" in the kzalloc() function.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments

Signed-off-by: Len Baker 
Reviewed-by: Gustavo A. R. Silva 
Signed-off-by: Gustavo A. R. Silva

eventfd: Make signal recursion protection a task bit

2021-08-27T23:33:02+00:00

The recursion protection for eventfd_signal() is based on a per CPU
variable and relies on the !RT semantics of spin_lock_irqsave() for
protecting this per CPU variable. On RT kernels spin_lock_irqsave() neither
disables preemption nor interrupts which allows the spin lock held section
to be preempted. If the preempting task invokes eventfd_signal() as well,
then the recursion warning triggers.

Paolo suggested to protect the per CPU variable with a local lock, but
that's heavyweight and actually not necessary. The goal of this protection
is to prevent the task stack from overflowing, which can be achieved with a
per task recursion protection as well.

Replace the per CPU variable with a per task bit similar to other recursion
protection bits like task_struct::in_page_owner. This works on both !RT and
RT kernels and removes as a side effect the extra per CPU storage.

No functional change for !RT kernels.

Reported-by: Daniel Bristot de Oliveira 
Signed-off-by: Thomas Gleixner 
Tested-by: Daniel Bristot de Oliveira 
Acked-by: Jason Wang 
Cc: Al Viro 
Link: https://lore.kernel.org/r/87wnp9idso.ffs@tglx

Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio"

2021-04-30T18:20:39+00:00

This reverts commit cd544fd1dc9293c6702fab6effa63dac1cc67e99.

As discussed in [1] this commit was a no-op because the mapping type was
checked in vma_to_resize before move_vma is ever called.  This meant that
vm_ops->mremap() would never be called on such mappings.  Furthermore,
we've since expanded support of MREMAP_DONTUNMAP to non-anonymous
mappings, and these special mappings are still protected by the existing
check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EINVAL.

1. https://lkml.org/lkml/2020/12/28/2340

Link: https://lkml.kernel.org/r/20210323182520.2712101-2-bgeffon@google.com
Signed-off-by: Brian Geffon 
Acked-by: Hugh Dickins 
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Alejandro Colomar 
Cc: Andrea Arcangeli 
Cc: Andy Lutomirski 
Cc: Axel Rasmussen 
Cc: "Kirill A . Shutemov" 
Cc: Lokesh Gidra 
Cc: Michael Kerrisk 
Cc: "Michael S . Tsirkin" 
Cc: Mike Rapoport 
Cc: Minchan Kim 
Cc: Peter Xu 
Cc: Sonny Rao 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2020-12-15T20:53:37+00:00

Merge misc updates from Andrew Morton:

 - a few random little subsystems

 - almost all of the MM patches which are staged ahead of linux-next
   material. I'll trickle to post-linux-next work in as the dependents
   get merged up.

Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).

* emailed patches from Andrew Morton : (200 commits)
  mm: cleanup kstrto*() usage
  mm: fix fall-through warnings for Clang
  mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
  mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
  mm:backing-dev: use sysfs_emit in macro defining functions
  mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
  mm: use sysfs_emit for struct kobject * uses
  mm: fix kernel-doc markups
  zram: break the strict dependency from lzo
  zram: add stat to gather incompressible pages since zram set up
  zram: support page writeback
  mm/process_vm_access: remove redundant initialization of iov_r
  mm/zsmalloc.c: rework the list_add code in insert_zspage()
  mm/zswap: move to use crypto_acomp API for hardware acceleration
  mm/zswap: fix passing zero to 'PTR_ERR' warning
  mm/zswap: make struct kernel_param_ops definitions const
  userfaultfd/selftests: hint the test runner on required privilege
  userfaultfd/selftests: fix retval check for userfaultfd_open()
  userfaultfd/selftests: always dump something in modes
  userfaultfd: selftests: make __{s,u}64 format specifiers portable
  ...