linux.git/fs/eventpoll.c, branch v3.6

eventpoll: use-after-possible-free in epoll_create1()

2012-08-22T14:26:55+00:00

As soon as we'd installed the file into descriptor table, it can
get closed by another thread.  Freeing ep in process...

Signed-off-by: Al Viro

PM: Rename CAP_EPOLLWAKEUP to CAP_BLOCK_SUSPEND

2012-07-17T19:37:27+00:00

As discussed in
http://thread.gmane.org/gmane.linux.kernel/1249726/focus=1288990,
the capability introduced in 4d7e30d98939a0340022ccd49325a3d70f7e0238
to govern EPOLLWAKEUP seems misnamed: this capability is about governing
the ability to suspend the system, not using a particular API flag
(EPOLLWAKEUP). We should make the name of the capability more general
to encourage reuse in related cases. (Whether or not this capability
should also be used to govern the use of /sys/power/wake_lock is a
question that needs to be separately resolved.)

This patch renames the capability to CAP_BLOCK_SUSPEND. In order to ensure
that the old capability name doesn't make it out into the wild, could you
please apply and push up the tree to ensure that it is incorporated
for the 3.5 release.

Signed-off-by: Michael Kerrisk 
Acked-by: Serge Hallyn 
Signed-off-by: Rafael J. Wysocki

HAVE_RESTORE_SIGMASK is defined on all architectures now

2012-06-01T16:58:46+00:00

Everyone either defines it in arch thread_info.h or has TIF_RESTORE_SIGMASK
and picks default set_restore_sigmask() in linux/thread_info.h.  Kill the
ifdefs, slap #error in linux/thread_info.h to catch breakage when new ones
get merged.

Signed-off-by: Al Viro

epoll: Fix user space breakage related to EPOLLWAKEUP

2012-05-22T18:57:06+00:00

Commit 4d7e30d (epoll: Add a flag, EPOLLWAKEUP, to prevent
suspend while epoll events are ready) caused some applications to
malfunction, because they set the bit corresponding to the new
EPOLLWAKEUP flag in their eventpoll flags and they don't have the
new CAP_EPOLLWAKEUP capability.

To prevent that from happening, change epoll_ctl() to clear
EPOLLWAKEUP in epds.events if the caller doesn't have the
CAP_EPOLLWAKEUP capability instead of failing and returning an
error code, which allows the affected applications to function
normally.

Reported-and-tested-by: Jiri Slaby 
Signed-off-by: Rafael J. Wysocki

epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready

2012-05-05T19:50:41+00:00

When an epoll_event, that has the EPOLLWAKEUP flag set, is ready, a
wakeup_source will be active to prevent suspend. This can be used to
handle wakeup events from a driver that support poll, e.g. input, if
that driver wakes up the waitqueue passed to epoll before allowing
suspend.

Signed-off-by: Arve Hjønnevåg 
Reviewed-by: NeilBrown 
Signed-off-by: Rafael J. Wysocki

epoll: clear the tfile_check_list on -ELOOP

2012-04-26T04:26:33+00:00

An epoll_ctl(,EPOLL_CTL_ADD,,) operation can return '-ELOOP' to prevent
circular epoll dependencies from being created.  However, in that case we
do not properly clear the 'tfile_check_list'.  Thus, add a call to
clear_tfile_check_list() for the -ELOOP case.

Signed-off-by: Jason Baron 
Reported-by: Yurij M. Plotnikov 
Cc: Nelson Elhage 
Cc: Davide Libenzi 
Tested-by: Alexandra N. Kossovsky 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system

2012-03-28T22:58:21+00:00

Pull "Disintegrate and delete asm/system.h" from David Howells:
 "Here are a bunch of patches to disintegrate asm/system.h into a set of
  separate bits to relieve the problem of circular inclusion
  dependencies.

  I've built all the working defconfigs from all the arches that I can
  and made sure that they don't break.

  The reason for these patches is that I recently encountered a circular
  dependency problem that came about when I produced some patches to
  optimise get_order() by rewriting it to use ilog2().

  This uses bitops - and on the SH arch asm/bitops.h drags in
  asm-generic/get_order.h by a circuituous route involving asm/system.h.

  The main difficulty seems to be asm/system.h.  It holds a number of
  low level bits with no/few dependencies that are commonly used (eg.
  memory barriers) and a number of bits with more dependencies that
  aren't used in many places (eg.  switch_to()).

  These patches break asm/system.h up into the following core pieces:

    (1) asm/barrier.h

        Move memory barriers here.  This already done for MIPS and Alpha.

    (2) asm/switch_to.h

        Move switch_to() and related stuff here.

    (3) asm/exec.h

        Move arch_align_stack() here.  Other process execution related bits
        could perhaps go here from asm/processor.h.

    (4) asm/cmpxchg.h

        Move xchg() and cmpxchg() here as they're full word atomic ops and
        frequently used by atomic_xchg() and atomic_cmpxchg().

    (5) asm/bug.h

        Move die() and related bits.

    (6) asm/auxvec.h

        Move AT_VECTOR_SIZE_ARCH here.

  Other arch headers are created as needed on a per-arch basis."

Fixed up some conflicts from other header file cleanups and moving code
around that has happened in the meantime, so David's testing is somewhat
weakened by that.  We'll find out anything that got broken and fix it..

* tag 'split-asm_system_h-for-linus-20120328' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-asm_system: (38 commits)
  Delete all instances of asm/system.h
  Remove all #inclusions of asm/system.h
  Add #includes needed to permit the removal of asm/system.h
  Move all declarations of free_initmem() to linux/mm.h
  Disintegrate asm/system.h for OpenRISC
  Split arch_align_stack() out from asm-generic/system.h
  Split the switch_to() wrapper out of asm-generic/system.h
  Move the asm-generic/system.h xchg() implementation to asm-generic/cmpxchg.h
  Create asm-generic/barrier.h
  Make asm-generic/cmpxchg.h #include asm-generic/cmpxchg-local.h
  Disintegrate asm/system.h for Xtensa
  Disintegrate asm/system.h for Unicore32 [based on ver #3, changed by gxt]
  Disintegrate asm/system.h for Tile
  Disintegrate asm/system.h for Sparc
  Disintegrate asm/system.h for SH
  Disintegrate asm/system.h for Score
  Disintegrate asm/system.h for S390
  Disintegrate asm/system.h for PowerPC
  Disintegrate asm/system.h for PA-RISC
  Disintegrate asm/system.h for MN10300
  ...

Remove all #inclusions of asm/system.h

2012-03-28T17:30:03+00:00

Remove all #inclusions of asm/system.h preparatory to splitting and killing
it.  Performed with the following command:

perl -p -i -e 's!^#\s*include\s*.*\n!!' `grep -Irl '^#\s*include\s*' *`

Signed-off-by: David Howells

epoll: remove unneeded variable in reverse_path_check()

2012-03-23T23:58:38+00:00

We never use the length variable.

Signed-off-by: Dan Carpenter 
Acked-by: Jason Baron 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: comment the funky #ifdef

2012-03-23T23:58:38+00:00

Looking for a bug in -rt, I stumbled across this code here from: commit
2dfa4eeab0fc ("epoll keyed wakeups: teach epoll about hints coming with
the wakeup key"), specifically:

  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
                                      unsigned long events, int subclass)
  {
         unsigned long flags;

         spin_lock_irqsave_nested(&wqueue->lock, flags, subclass);
         wake_up_locked_poll(wqueue, events);
         spin_unlock_irqrestore(&wqueue->lock, flags);
  }
  #else
  static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
                                      unsigned long events, int subclass)
  {
         wake_up_poll(wqueue, events);
  }
  #endif

You change the function of ep_wake_up_nested() depending on whether
CONFIG_DEBUG_LOCK_ALLOC is set or not.  This looks awfully suspicious,
and there's no comment to explain why.  I initially thought that this
was trying to fool lockdep, and hiding a real bug.

Investigating it, I found the creation of wake_up_nested() (which no
longer exists) but was created for the sole purpose of epoll and its
strange wake ups, as explained in commit 0ccf831cbee9 ("lockdep:
annotate epoll")

Although the commit message says "annotate epoll" the change log is much
better at explaining what is happening than what is in the actual code.
Thus a comment is really necessary here.  And to save the time of other
developers from having to go trudging through the git logs trying to
figure out why this code exists.

I took parts of the change log and placed it into a comment above the
affected code.  This will make the description of what is happening more
visible to new developers that have to look at this code for the first
time.

Signed-off-by: Steven Rostedt 
Cc: Davide Libenzi 
Cc: Peter Zijlstra 
Cc: Alan Cox 
Cc: Ingo Molnar 
Cc: David Miller 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds