linux-stable.git/fs/timerfd.c, branch v3.16.75

timerfd: Protect the might cancel mechanism proper

2017-08-26T01:14:49+00:00

commit 1e38da300e1e395a15048b0af1e5305bd91402f6 upstream.

The handling of the might_cancel queueing is not properly protected, so
parallel operations on the file descriptor can race with each other and
lead to list corruptions or use after free.

Protect the context for these operations with a seperate lock.

The wait queue lock cannot be reused for this because that would create a
lock inversion scenario vs. the cancel lock. Replacing might_cancel with an
atomic (atomic_t or atomic bit) does not help either because it still can
race vs. the actual list operation.

Reported-by: Dmitry Vyukov 
Signed-off-by: Thomas Gleixner 
Cc: "linux-fsdevel@vger.kernel.org"
Cc: syzkaller 
Cc: Al Viro 
Cc: linux-fsdevel@vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1701311521430.3457@nanos
Signed-off-by: Thomas Gleixner 
Signed-off-by: Ben Hutchings

timerfd: support CLOCK_BOOTTIME clock

2014-01-24T00:57:40+00:00

Add CLOCK_BOOTTIME support to timerfd

Signed-off-by: Greg Hackmann 
Signed-off-by: John Stultz

timerfd: Add alarm timers

2013-05-29T19:57:34+00:00

Add support for clocks CLOCK_REALTIME_ALARM and CLOCK_BOOTTIME_ALARM,
thereby enabling wakeup alarm timers via file descriptors.

Signed-off-by: Todd Poynor 
Signed-off-by: John Stultz

compat: restore timerfd settime and gettime compat syscalls

2013-03-02T14:35:13+00:00

Both compat syscalls got lost with 9d94b9e2 "switch timerfd compat syscalls
to COMPAT_SYSCALL_DEFINE" because of a typo:
COMPAT instead of CONFIG_COMPAT.

Signed-off-by: Heiko Carstens 
Signed-off-by: Al Viro

switch timerfd compat syscalls to COMPAT_SYSCALL_DEFINE

2013-02-03T20:09:25+00:00

... and move them over to fs/timerfd.c.  Cleaner and easier
that way...

Signed-off-by: Al Viro

switch simple cases of fget_light to fdget

2012-09-27T02:20:08+00:00

Signed-off-by: Al Viro

switch timerfd_[sg]ettime(2) to fget_light()

2012-09-27T01:10:08+00:00

Signed-off-by: Al Viro

timerfd: Fix wakeup of processes when timer is cancelled on clock change

2011-06-14T09:46:14+00:00

Currently processes waiting with poll on cancelable timerfd timers are
not woken up when the timers are canceled. When the system time is set
the clock_was_set() function calls timerfd_clock_was_set() to cancel
and wake up processes waiting on potential cancelable timerfd
timers. However the wake up currently has no effect because in the
case of timerfd_read it is dependent on ctx->ticks not being
0. timerfd_poll also requires ctx->ticks being non zero. As a
consequence processes waiting on cancelable timers only get woken up
when the timers expire. This patch fixes this by incrementing
ctx->ticks before calling wake_up.

Signed-off-by: Max Asbock 
Cc: kay.sievers@vrfy.org
Cc: virtuoso@slind.org
Cc: johnstul 
Link: http://lkml.kernel.org/r/1307985512.4710.41.camel@w-amax.beaverton.ibm.com
Signed-off-by: Thomas Gleixner

timerfd: Manage cancelable timers in timerfd

2011-05-23T11:59:53+00:00

Peter is concerned about the extra scan of CLOCK_REALTIME_COS in the
timer interrupt. Yes, I did not think about it, because the solution
was so elegant. I didn't like the extra list in timerfd when it was
proposed some time ago, but with a rcu based list the list walk it's
less horrible than the original global lock, which was held over the
list iteration.

Requested-by: Peter Zijlstra 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Peter Zijlstra

timerfd: Allow timers to be cancelled when clock was set

2011-05-02T19:39:15+00:00

Some applications must be aware of clock realtime being set
backward. A simple example is a clock applet which arms a timer for
the next minute display. If clock realtime is set backward then the
applet displays a stale time for the amount of time which the clock
was set backwards. Due to that applications poll the time because we
don't have an interface.

Extend the timerfd interface by adding a flag which puts the timer
onto a different internal realtime clock. All timers on this clock are
expired whenever the clock was set.

The timerfd core records the monotonic offset when the timer is
created. When the timer is armed, then the current offset is compared
to the previous recorded offset. When it has changed, then
timerfd_settime returns -ECANCELED. When a timer is read the offset is
compared and if it changed -ECANCELED returned to user space. Periodic
timers are not rearmed in the cancelation case.

Signed-off-by: Thomas Gleixner 
Acked-by: John Stultz 
Cc: Chris Friesen 
Tested-by: Kay Sievers 
Cc: "Kirill A. Shutemov" 
Cc: Peter Zijlstra 
Cc: Davide Libenzi 
Reviewed-by: Alexander Shishkin 
Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1104271359580.3323%40ionos%3E
Signed-off-by: Thomas Gleixner