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  1. 12 4月, 2015 1 次提交
  3. 07 3月, 2015 1 次提交
  5. 20 2月, 2015 1 次提交
  7. 14 10月, 2014 1 次提交
    • O
      coredump: add %i/%I in core_pattern to report the tid of the crashed thread · b03023ec
      由 Oleg Nesterov 提交于 
      format_corename() can only pass the leader's pid to the core handler,
but there is no simple way to figure out which thread originated the
coredump.

As Jan explains, this also means that there is no simple way to create
the backtrace of the crashed process:

As programs are mostly compiled with implicit gcc -fomit-frame-pointer
one needs program's .eh_frame section (equivalently PT_GNU_EH_FRAME
segment) or .debug_frame section.  .debug_frame usually is present only
in separate debug info files usually not even installed on the system.
While .eh_frame is a part of the executable/library (and it is even
always mapped for C++ exceptions unwinding) it no longer has to be
present anywhere on the disk as the program could be upgraded in the
meantime and the running instance has its executable file already
unlinked from disk.

One possibility is to echo 0x3f >/proc/*/coredump_filter and dump all
the file-backed memory including the executable's .eh_frame section.
But that can create huge core files, for example even due to mmapped
data files.

Other possibility would be to read .eh_frame from /proc/PID/mem at the
core_pattern handler time of the core dump.  For the backtrace one needs
to read the register state first which can be done from core_pattern
handler:

    ptrace(PTRACE_SEIZE, tid, 0, PTRACE_O_TRACEEXIT)
    close(0);    // close pipe fd to resume the sleeping dumper
    waitpid();   // should report EXIT
    PTRACE_GETREGS or other requests

The remaining problem is how to get the 'tid' value of the crashed
thread.  It could be read from the first NT_PRSTATUS note of the core
file but that makes the core_pattern handler complicated.

Unfortunately %t is already used so this patch uses %i/%I.

Automatic Bug Reporting Tool (https://github.com/abrt/abrt/wiki/overview)
is experimenting with this.  It is using the elfutils
(https://fedorahosted.org/elfutils/) unwinder for generating the
backtraces.  Apart from not needing matching executables as mentioned
above, another advantage is that we can get the backtrace without saving
the core (which might be quite large) to disk.

[mmilata@redhat.com: final paragraph of changelog]
Signed-off-by: NJan Kratochvil <jan.kratochvil@redhat.com>
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Martin Milata <mmilata@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b03023ec
  9. 24 7月, 2014 1 次提交
  11. 20 4月, 2014 1 次提交
    • E
      coredump: fix va_list corruption · 404ca80e
      由 Eric Dumazet 提交于 
      A va_list needs to be copied in case it needs to be used twice.

Thanks to Hugh for debugging this issue, leading to various panics.

Tested:

  lpq84:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h" >/proc/sys/kernel/core_pattern

'produce_core' is simply : main() { *(int *)0 = 1;}

  lpq84:~# ./produce_core
  Segmentation fault (core dumped)
  lpq84:~# dmesg | tail -1
  [  614.352947] Core dump to |/foobar12345 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 (null) pipe failed

Notice the last argument was replaced by a NULL (we were lucky enough to
not crash, but do not try this on your production machine !)

After fix :

  lpq83:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h %h" >/proc/sys/kernel/core_pattern
  lpq83:~# ./produce_core
  Segmentation fault
  lpq83:~# dmesg | tail -1
  [  740.800441] Core dump to |/foobar12345 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 pipe failed

Fixes: 5fe9d8ca ("coredump: cn_vprintf() has no reason to call vsnprintf() twice")
Signed-off-by: NEric Dumazet <edumazet@google.com>
Diagnosed-by: NHugh Dickins <hughd@google.com>
Acked-by: NOleg Nesterov <oleg@redhat.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org # 3.11+
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      404ca80e
  13. 24 1月, 2014 1 次提交
  15. 16 11月, 2013 2 次提交
  17. 09 11月, 2013 5 次提交
  19. 25 10月, 2013 1 次提交
  21. 12 9月, 2013 1 次提交
  23. 04 7月, 2013 6 次提交
  25. 05 5月, 2013 1 次提交
  27. 01 5月, 2013 8 次提交
    • O
      coredump: change wait_for_dump_helpers() to use wait_event_interruptible() · dc7ee2aa
      由 Oleg Nesterov 提交于 
      wait_for_dump_helpers() calls wake_up/kill_fasync from inside the
wait_event-like loop.  This is not needed and in fact this is not
strictly correct, we can/should do this only once after we change
pipe->writers.  We could even check if it becomes zero.

Change this code to use use wait_event_interruptible(), this can also
help to make this wait freezable.

With this patch we check pipe->readers without pipe_lock(), this is
fine.  Once we see pipe->readers == 1 we know that the handler
decremented the counter, this is all we need.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      dc7ee2aa
    • O
      coredump: factor out the setting of PF_DUMPCORE · 079148b9
      由 Oleg Nesterov 提交于 
      Cleanup.  Every linux_binfmt->core_dump() sets PF_DUMPCORE, move this into
zap_threads() called by do_coredump().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      079148b9
    • O
      coredump: introduce dump_interrupted() · 528f827e
      由 Oleg Nesterov 提交于 
      By discussion with Mandeep.

Change dump_write(), dump_seek() and do_coredump() to check
signal_pending() and abort if it is true.  dump_seek() does this only
before f_op->llseek(), otherwise it relies on dump_write().

We need this change to ensure that the coredump won't delay suspend, and
to ensure it reacts to SIGKILL "quickly enough", a core dump can take a
lot of time.  In particular this can help oom-killer.

We add the new trivial helper, dump_interrupted() to add the comments and
to simplify the potential freezer changes.  Perhaps it will have more
callers.

Ideally it should do try_to_freeze() but then we need the unpleasant
changes in dump_write() and wait_for_dump_helpers().  It is not trivial to
change dump_write() to restart if f_op->write() fails because of
freezing().  We need to handle the short writes, we need to clear
TIF_SIGPENDING (and we can't rely on recalc_sigpending() unless we change
it to check PF_DUMPCORE).  And if the buggy f_op->write() sets
TIF_SIGPENDING we can not distinguish this case from the race with
freeze_task() + __thaw_task().

So we simply accept the fact that the freezer can truncate a core-dump but
at least you can reliably suspend.  Hopefully we can tolerate this
unlikely case and the necessary complications doesn't worth a trouble.
But if we decide to make the coredumping freezable later we can do this on
top of this change.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Acked-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      528f827e
    • O
      coredump: sanitize the setting of signal->group_exit_code · acdedd99
      由 Oleg Nesterov 提交于 
      Now that the coredumping process can be SIGKILL'ed, the setting of
->group_exit_code in do_coredump() can race with complete_signal() and
SIGKILL or 0x80 can be "lost", or wait(status) can report status ==
SIGKILL | 0x80.

But the main problem is that it is not clear to me what should we do if
binfmt->core_dump() succeeds but SIGKILL was sent, that is why this patch
comes as a separate change.

This patch adds 0x80 if ->core_dump() succeeds and the process was not
killed.  But perhaps we can (should?) re-set ->group_exit_code changed by
SIGKILL back to "siginfo->si_signo |= 0x80" in case when core_dumped == T.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      acdedd99
    • O
      coredump: ensure that SIGKILL always kills the dumping thread · 6cd8f0ac
      由 Oleg Nesterov 提交于 
      prepare_signal() blesses SIGKILL sent to the dumping process but this
signal can be "lost" anyway.  The problems is, complete_signal() sees
SIGNAL_GROUP_EXIT and skips the "kill them all" logic.  And even if the
dumping process is single-threaded (so the target is always "correct"),
the group-wide SIGKILL is not recorded in task->pending and thus
__fatal_signal_pending() won't be true.  A multi-threaded case has even
more problems.

And even ignoring all technical details, SIGNAL_GROUP_EXIT doesn't look
right to me.  This coredumping process is not exiting yet, it can do a lot
of work dumping the core.

With this patch the dumping process doesn't have SIGNAL_GROUP_EXIT, we set
signal->group_exit_task instead.  This makes signal_group_exit() true and
thus this should equally close the races with exit/exec/stop but allows to
kill the dumping thread reliably.

Notes:
	- It is not clear what should we do with ->group_exit_code
	  if the dumper was killed, see the next change.

	- we need more (hopefully straightforward) changes to ensure
	  that SIGKILL actually interrupts the coredump. Basically we
	  need to check __fatal_signal_pending() in dump_write() and
	  dump_seek().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      6cd8f0ac
    • O
      coredump: only SIGKILL should interrupt the coredumping task · 403bad72
      由 Oleg Nesterov 提交于 
      There are 2 well known and ancient problems with coredump/signals, and a
lot of related bug reports:

- do_coredump() clears TIF_SIGPENDING but of course this can't help
  if, say, SIGCHLD comes after that.

  In this case the coredump can fail unexpectedly. See for example
  wait_for_dump_helper()->signal_pending() check but there are other
  reasons.

- At the same time, dumping a huge core on the slow media can take a
  lot of time/resources and there is no way to kill the coredumping
  task reliably. In particular this is not oom_kill-friendly.

This patch tries to fix the 1st problem, and makes the preparation for the
next changes.

We add the new SIGNAL_GROUP_COREDUMP flag set by zap_threads() to indicate
that this process dumps the core.  prepare_signal() checks this flag and
nacks any signal except SIGKILL.

Note that this check tries to be conservative, in the long term we should
probably treat the SIGNAL_GROUP_EXIT case equally but this needs more
discussion.  See marc.info/?l=linux-kernel&m=120508897917439

Notes:
	- recalc_sigpending() doesn't check SIGNAL_GROUP_COREDUMP.
	  The patch assumes that dump_write/etc paths should never
	  call it, but we can change it as well.

	- There is another source of TIF_SIGPENDING, freezer. This
	  will be addressed separately.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Tested-by: NMandeep Singh Baines <msb@chromium.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Neil Horman <nhorman@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      403bad72
    • L
      usermodehelper: split remaining calls to call_usermodehelper_fns() · 907ed132
      由 Lucas De Marchi 提交于 
      These are the only users of call_usermodehelper_fns().  This function
suffers from not being able to determine if the cleanup is called.  Even
if in this places the cleanup pointer is NULL, convert them to use the
separate call_usermodehelper_setup() + call_usermodehelper_exec()
functions so we can remove the _fns variant.
Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      907ed132
    • L
      coredump: remove trailling whitespace · fb96c475
      由 Lucas De Marchi 提交于 
      Signed-off-by: NLucas De Marchi <lucas.demarchi@profusion.mobi>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: James Morris <james.l.morris@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      fb96c475
  29. 10 4月, 2013 2 次提交
  31. 28 2月, 2013 1 次提交
  33. 23 2月, 2013 1 次提交
  35. 29 11月, 2012 1 次提交
  37. 17 10月, 2012 1 次提交
    • A
      fix a leak in replace_fd() users · 45525b26
      由 Al Viro 提交于 
      replace_fd() began with "eats a reference, tries to insert into
descriptor table" semantics; at some point I'd switched it to
much saner current behaviour ("try to insert into descriptor
table, grabbing a new reference if inserted; caller should do
fput() in any case"), but forgot to update the callers.
Mea culpa...

[Spotted by Pavel Roskin, who has really weird system with pipe-fed
coredumps as part of what he considers a normal boot ;-)]
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      45525b26
  39. 06 10月, 2012 3 次提交