linux.git/kernel/futex/core.c, branch v6.6.131

futex: Don't include process MM in futex key on no-MMU

2023-11-20T10:58:53+00:00

[ Upstream commit c73801ae4f22b390228ebf471d55668e824198b6 ]

On no-MMU, all futexes are treated as private because there is no need
to map a virtual address to physical to match the futex across
processes. This doesn't quite work though, because private futexes
include the current process's mm_struct as part of their key. This makes
it impossible for one process to wake up a shared futex being waited on
in another process.

Fix this bug by excluding the mm_struct from the key. With
a single address space, the futex address is already a unique key.

Fixes: 784bdf3bb694 ("futex: Assume all mappings are private on !MMU systems")
Signed-off-by: Ben Wolsieffer 
Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Cc: André Almeida 
Link: https://lore.kernel.org/r/20231019204548.1236437-2-ben.wolsieffer@hefring.com
Signed-off-by: Sasha Levin

mm/mm_init.c: remove obsolete macro HASH_SMALL

2023-08-18T17:12:07+00:00

HASH_SMALL only works when parameter numentries is 0. But the sole caller
futex_init() never calls alloc_large_system_hash() with numentries set to
0. So HASH_SMALL is obsolete and remove it.

Link: https://lkml.kernel.org/r/20230625021323.849147-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin 
Reviewed-by: Mike Rapoport (IBM) 
Cc: André Almeida 
Cc: Darren Hart 
Cc: Davidlohr Bueso 
Cc: Ingo Molnar 
Cc: Miaohe Lin 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton

futex: Resend potentially swallowed owner death notification

2022-12-02T11:20:24+00:00

Commit ca16d5bee598 ("futex: Prevent robust futex exit race") addressed
two cases when tasks waiting on a robust non-PI futex remained blocked
despite the futex not being owned anymore:

* if the owner died after writing zero to the futex word, but before
  waking up a waiter

* if a task waiting on the futex was woken up, but died before updating
  the futex word (effectively swallowing the notification without acting
  on it)

In the second case, the task could be woken up either by the previous
owner (after the futex word was reset to zero) or by the kernel (after
the OWNER_DIED bit was set and the TID part of the futex word was reset
to zero) if the previous owner died without the resetting the futex.

Because the referenced commit wakes up a potential waiter only if the
whole futex word is zero, the latter subcase remains unaddressed.

Fix this by looking only at the TID part of the futex when deciding
whether a wake up is needed.

Fixes: ca16d5bee598 ("futex: Prevent robust futex exit race")
Signed-off-by: Alexey Izbyshev 
Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20221111215439.248185-1-izbyshev@ispras.ru

mm/truncate: Inline invalidate_complete_page() into its one caller

2022-03-21T16:59:01+00:00

invalidate_inode_page() is the only caller of invalidate_complete_page()
and inlining it reveals that the first check is unnecessary (because we
hold the page locked, and we just retrieved the mapping from the page).
Actually, it does make a difference, in that tail pages no longer fail
at this check, so it's now possible to remove a tail page from a mapping.

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: John Hubbard 
Reviewed-by: Christoph Hellwig

Merge branch 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2022-01-17T03:49:30+00:00

Pull signal/exit/ptrace updates from Eric Biederman:
 "This set of changes deletes some dead code, makes a lot of cleanups
  which hopefully make the code easier to follow, and fixes bugs found
  along the way.

  The end-game which I have not yet reached yet is for fatal signals
  that generate coredumps to be short-circuit deliverable from
  complete_signal, for force_siginfo_to_task not to require changing
  userspace configured signal delivery state, and for the ptrace stops
  to always happen in locations where we can guarantee on all
  architectures that the all of the registers are saved and available on
  the stack.

  Removal of profile_task_ext, profile_munmap, and profile_handoff_task
  are the big successes for dead code removal this round.

  A bunch of small bug fixes are included, as most of the issues
  reported were small enough that they would not affect bisection so I
  simply added the fixes and did not fold the fixes into the changes
  they were fixing.

  There was a bug that broke coredumps piped to systemd-coredump. I
  dropped the change that caused that bug and replaced it entirely with
  something much more restrained. Unfortunately that required some
  rebasing.

  Some successes after this set of changes: There are few enough calls
  to do_exit to audit in a reasonable amount of time. The lifetime of
  struct kthread now matches the lifetime of struct task, and the
  pointer to struct kthread is no longer stored in set_child_tid. The
  flag SIGNAL_GROUP_COREDUMP is removed. The field group_exit_task is
  removed. Issues where task->exit_code was examined with
  signal->group_exit_code should been examined were fixed.

  There are several loosely related changes included because I am
  cleaning up and if I don't include them they will probably get lost.

  The original postings of these changes can be found at:
     https://lkml.kernel.org/r/87a6ha4zsd.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87bl1kunjj.fsf@email.froward.int.ebiederm.org
     https://lkml.kernel.org/r/87r19opkx1.fsf_-_@email.froward.int.ebiederm.org

  I trimmed back the last set of changes to only the obviously correct
  once. Simply because there was less time for review than I had hoped"

* 'signal-for-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (44 commits)
  ptrace/m68k: Stop open coding ptrace_report_syscall
  ptrace: Remove unused regs argument from ptrace_report_syscall
  ptrace: Remove second setting of PT_SEIZED in ptrace_attach
  taskstats: Cleanup the use of task->exit_code
  exit: Use the correct exit_code in /proc//stat
  exit: Fix the exit_code for wait_task_zombie
  exit: Coredumps reach do_group_exit
  exit: Remove profile_handoff_task
  exit: Remove profile_task_exit & profile_munmap
  signal: clean up kernel-doc comments
  signal: Remove the helper signal_group_exit
  signal: Rename group_exit_task group_exec_task
  coredump: Stop setting signal->group_exit_task
  signal: Remove SIGNAL_GROUP_COREDUMP
  signal: During coredumps set SIGNAL_GROUP_EXIT in zap_process
  signal: Make coredump handling explicit in complete_signal
  signal: Have prepare_signal detect coredumps using signal->core_state
  signal: Have the oom killer detect coredumps using signal->core_state
  exit: Move force_uaccess back into do_exit
  exit: Guarantee make_task_dead leaks the tsk when calling do_task_exit
  ...

exit: Move oops specific logic from do_exit into make_task_dead

2021-12-13T18:04:45+00:00

The beginning of do_exit has become cluttered and difficult to read as
it is filled with checks to handle things that can only happen when
the kernel is operating improperly.

Now that we have a dedicated function for cleaning up a task when the
kernel is operating improperly move the checks there.

Signed-off-by: "Eric W. Biederman"

futex: Remove futex_cmpxchg detection

2021-11-24T23:02:28+00:00

Now that all architectures have a working futex implementation in any
configuration, remove the runtime detection code.

Signed-off-by: Arnd Bergmann 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Russell King (Oracle) 
Acked-by: Vineet Gupta 
Acked-by: Max Filippov 
Acked-by: Christian Borntraeger 
Link: https://lore.kernel.org/r/20211026100432.1730393-2-arnd@kernel.org

futex: Split out wait/wake

2021-10-07T11:51:11+00:00

Move the wait/wake bits into their own file.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: André Almeida 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: André Almeida 
Link: https://lore.kernel.org/r/20210923171111.300673-15-andrealmeid@collabora.com

futex: Split out requeue

2021-10-07T11:51:10+00:00

Move all the requeue bits into their own file.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: André Almeida 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: André Almeida 
Link: https://lore.kernel.org/r/20210923171111.300673-14-andrealmeid@collabora.com

futex: Rename mark_wake_futex()

2021-10-07T11:51:10+00:00

In order to prepare introducing these symbols into the global
namespace; rename:

  s/mark_wake_futex/futex_wake_mark/g

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: André Almeida 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: André Almeida 
Link: https://lore.kernel.org/r/20210923171111.300673-13-andrealmeid@collabora.com