linux-stable.git/include/linux/signal.h, branch v3.2.102

fcntl: Don't use ambiguous SIG_POLL si_codes

2017-11-26T13:51:01+00:00

commit d08477aa975e97f1dc64c0ae59cebf98520456ce upstream.

We have a weird and problematic intersection of features that when
they all come together result in ambiguous siginfo values, that
we can not support properly.

- Supporting fcntl(F_SETSIG,...) with arbitrary valid signals.

- Using positive values for POLL_IN, POLL_OUT, POLL_MSG, ..., etc
  that imply they are signal specific si_codes and using the
  aforementioned arbitrary signal to deliver them.

- Supporting injection of arbitrary siginfo values for debugging and
  checkpoint/restore.

The result is that just looking at siginfo si_codes of 1 to 6 are
ambigious.  It could either be a signal specific si_code or it could
be a generic si_code.

For most of the kernel this is a non-issue but for sending signals
with siginfo it is impossible to play back the kernel signals and
get the same result.

Strictly speaking when the si_code was changed from SI_SIGIO to
POLL_IN and friends between 2.2 and 2.4 this functionality was not
ambiguous, as only real time signals were supported.  Before 2.4 was
released the kernel began supporting siginfo with non realtime signals
so they could give details of why the signal was sent.

The result is that if F_SETSIG is set to one of the signals with signal
specific si_codes then user space can not know why the signal was sent.

I grepped through a bunch of userspace programs using debian code
search to get a feel for how often people choose a signal that results
in an ambiguous si_code.  I only found one program doing so and it was
using SIGCHLD to test the F_SETSIG functionality, and did not appear
to be a real world usage.

Therefore the ambiguity does not appears to be a real world problem in
practice.  Remove the ambiguity while introducing the smallest chance
of breakage by changing the si_code to SI_SIGIO when signals with
signal specific si_codes are targeted.

Fixes: v2.3.40 -- Added support for queueing non-rt signals
Fixes: v2.3.21 -- Changed the si_code from SI_SIGIO
Signed-off-by: "Eric W. Biederman" 
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings

signal: move the "sig < SIGRTMIN" check into siginmask(sig)

2017-11-26T13:51:01+00:00

commit 5c8ccefdf46c5f87d87b694c7fbc04941c2c99a5 upstream.

All the users of siginmask() must ensure that sig < SIGRTMIN.  sig_fatal()
doesn't and this is wrong:

	UBSAN: Undefined behaviour in kernel/signal.c:911:6
	shift exponent 32 is too large for 32-bit type 'long unsigned int'

the patch doesn't add the neccesary check to sig_fatal(), it moves the
check into siginmask() and updates other callers.

Link: http://lkml.kernel.org/r/20160517195052.GA15187@redhat.com
Reported-by: Meelis Roos 
Signed-off-by: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Ben Hutchings

Merge branch 'ptrace' of git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc

2011-05-20T20:33:21+00:00

* 'ptrace' of git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc: (41 commits)
  signal: trivial, fix the "timespec declared inside parameter list" warning
  job control: reorganize wait_task_stopped()
  ptrace: fix signal->wait_chldexit usage in task_clear_group_stop_trapping()
  signal: sys_sigprocmask() needs retarget_shared_pending()
  signal: cleanup sys_sigprocmask()
  signal: rename signandsets() to sigandnsets()
  signal: do_sigtimedwait() needs retarget_shared_pending()
  signal: introduce do_sigtimedwait() to factor out compat/native code
  signal: sys_rt_sigtimedwait: simplify the timeout logic
  signal: cleanup sys_rt_sigprocmask()
  x86: signal: sys_rt_sigreturn() should use set_current_blocked()
  x86: signal: handle_signal() should use set_current_blocked()
  signal: sigprocmask() should do retarget_shared_pending()
  signal: sigprocmask: narrow the scope of ->siglock
  signal: retarget_shared_pending: optimize while_each_thread() loop
  signal: retarget_shared_pending: consider shared/unblocked signals only
  signal: introduce retarget_shared_pending()
  ptrace: ptrace_check_attach() should not do s/STOPPED/TRACED/
  signal: Turn SIGNAL_STOP_DEQUEUED into GROUP_STOP_DEQUEUED
  signal: do_signal_stop: Remove the unneeded task_clear_group_stop_pending()
  ...

signal.h need a definition of struct task_struct

2011-05-20T01:22:20+00:00

This fixes these build errors on powerpc:

  In file included from arch/powerpc/mm/fault.c:18:
  include/linux/signal.h:239: error: 'struct task_struct' declared inside parameter list
  include/linux/signal.h:239: error: its scope is only this definition or declaration, which is probably not what you want
  include/linux/signal.h:240: error: 'struct task_struct' declared inside parameter list
  ..

Exposed by commit e66eed651fd1 ("list: remove prefetching from regular
list iterators"), which removed the include of  from
.

Without that, linux/signal.h no longer accidentally got the declaration
of 'struct task_struct'.

Fix by properly declaring the struct, rather than introducing any new
header file dependency.

Signed-off-by: Stephen Rothwell 
Signed-off-by: Linus Torvalds

signal: trivial, fix the "timespec declared inside parameter list" warning

2011-05-18T13:08:03+00:00

Fix the compile warning, do_sigtimedwait(struct timespec *) in signal.h
needs the forward declaration of timespec.

Reported-and-acked-by: Mike Frysinger 
Signed-off-by: Oleg Nesterov

signal: rename signandsets() to sigandnsets()

2011-04-28T11:01:39+00:00

As Tejun and Linus pointed out, "nand" is the wrong name for "x & ~y",
it should be "andn". Rename signandsets() as suggested.

Suggested-by: Tejun Heo 
Signed-off-by: Oleg Nesterov 
Acked-by: Tejun Heo

signal: introduce do_sigtimedwait() to factor out compat/native code

2011-04-28T11:01:38+00:00

Factor out the common code in sys_rt_sigtimedwait/compat_sys_rt_sigtimedwait
to the new helper, do_sigtimedwait().

Add the comment to document the extra tick we add to timespec_to_jiffies(ts),
thanks to Linus who explained this to me.

Perhaps it would be better to move compat_sys_rt_sigtimedwait() into
signal.c under CONFIG_COMPAT, then we can make do_sigtimedwait() static.

Signed-off-by: Oleg Nesterov 
Acked-by: Tejun Heo 
Reviewed-by: Matt Fleming

signal: sigprocmask() should do retarget_shared_pending()

2011-04-28T11:01:37+00:00

In short, almost every changing of current->blocked is wrong, or at least
can lead to the unexpected results.

For example. Two threads T1 and T2, T1 sleeps in sigtimedwait/pause/etc.
kill(tgid, SIG) can pick T2 for TIF_SIGPENDING. If T2 calls sigprocmask()
and blocks SIG before it notices the pending signal, nobody else can handle
this pending shared signal.

I am not sure this is bug, but at least this looks strange imho. T1 should
not sleep forever, there is a signal which should wake it up.

This patch moves the code which actually changes ->blocked into the new
helper, set_current_blocked() and changes this code to call
retarget_shared_pending() as exit_signals() does. We should only care about
the signals we just blocked, we use "newset & ~current->blocked" as a mask.

We do not check !sigisemptyset(newblocked), retarget_shared_pending() is
cheap unless mask & shared_pending.

Note: for this particular case we could simply change sigprocmask() to
return -EINTR if signal_pending(), but then we should change other callers
and, more importantly, if we need this fix then set_current_blocked() will
have more callers and some of them can't restart. See the next patch as a
random example.

Signed-off-by: Oleg Nesterov 
Reviewed-by: Matt Fleming 
Acked-by: Tejun Heo

sysctl extern cleanup: signal

2010-03-12T23:52:44+00:00

Extern declarations in sysctl.c should be moved to their own header file,
and then include them in relavant .c files.

Move print_fatal_signals extern declaration to linux/signal.h

Signed-off-by: Dave Young 
Cc: Oleg Nesterov 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

signals: introduce do_send_sig_info() helper

2009-09-24T14:21:01+00:00

Introduce do_send_sig_info() and convert group_send_sig_info(),
send_sig_info(), do_send_specific() to use this helper.

Hopefully it will have more users soon, it allows to specify
specific/group behaviour via "bool group" argument.

Shaves 80 bytes from .text.

Signed-off-by: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: stephane eranian 
Cc: Ingo Molnar 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds