linux-stable.git/arch/um/os-Linux, branch v4.1 Linux kernel stable tree um: Move uml_postsetup in the init_thread stack 2015-04-13T19:17:44+00:00 Thomas Meyer thomas@m3y3r.de 2015-03-28T08:59:46+00:00 33bbc3065414722065a20cbdbeaf352173e72f39 atomic_notifier_chain_register() and uml_postsetup() do call kernel code that rely on the "current" kernel macro and a valid task_struct resp. thread_info struct. Give those functions a valid stack by moving uml_postsetup() in the init_thread stack. This moves enables a panic() call in this early code to generate a valid stacktrace, instead of crashing. E.g. when an UML kernel is started with an initrd but too few physical memory the panic() call get's actually processed. Signed-off-by: Thomas Meyer <thomas@m3y3r.de> Signed-off-by: Richard Weinberger <richard@nod.at> 
atomic_notifier_chain_register() and uml_postsetup() do call kernel code
that rely on the "current" kernel macro and a valid task_struct resp.
thread_info struct. Give those functions a valid stack by moving
uml_postsetup() in the init_thread stack. This moves enables a panic()
call in this early code to generate a valid stacktrace, instead of
crashing.
E.g. when an UML kernel is started with an initrd but too few physical
memory the panic() call get's actually processed.

Signed-off-by: Thomas Meyer <thomas@m3y3r.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: Remove SKAS3/4 support 2015-04-13T19:00:53+00:00 Richard Weinberger richard@nod.at 2015-03-18T20:31:27+00:00 d0b5e15f0c0fdd759dd3dd48dc2dc2e7199e0da0 Before we had SKAS0 UML had two modes of operation TT (tracing thread) and SKAS3/4 (separated kernel address space). TT was known to be insecure and got removed a long time ago. SKAS3/4 required a few (3 or 4) patches on the host side which never went mainline. The last host patch is 10 years old. With SKAS0 mode (separated kernel address space using 0 host patches), default since 2005, SKAS3/4 is obsolete and can be removed. Signed-off-by: Richard Weinberger <richard@nod.at> 
Before we had SKAS0 UML had two modes of operation
TT (tracing thread) and SKAS3/4 (separated kernel address space).
TT was known to be insecure and got removed a long time ago.
SKAS3/4 required a few (3 or 4) patches on the host side which never went
mainline. The last host patch is 10 years old.

With SKAS0 mode (separated kernel address space using 0 host patches),
default since 2005, SKAS3/4 is obsolete and can be removed.

Signed-off-by: Richard Weinberger <richard@nod.at>
Revert "um: Fix wait_stub_done() error handling" 2014-07-20T10:56:34+00:00 Richard Weinberger richard@nod.at 2014-07-20T10:56:34+00:00 ae5db6d12341684913a78b6537c0b9c22c999b5c This reverts commit 0974a9cadc7886f7baaa458bb0c89f5c5f9d458e. The real for for that issue is to release current->mm->mmap_sem in fix_range_common(). Signed-off-by: Richard Weinberger <richard@nod.at> 
This reverts commit 0974a9cadc7886f7baaa458bb0c89f5c5f9d458e.
The real for for that issue is to release current->mm->mmap_sem in
fix_range_common().

Signed-off-by: Richard Weinberger <richard@nod.at>
um: Memory corruption on startup 2014-04-20T21:57:21+00:00 Anton Ivanov antivano@cisco.com 2014-03-07T18:37:47+00:00 0565103d1adbd765ca45248d04c327c076dd1571 The reverse case of this race (you must msync before read) is well known. This is the not so common one. It can be triggered only on systems which do a lot of task switching and only at UML startup. If you are starting 200+ UMLs ~ 0.5% will always die without this fix. Signed-off-by: Anton Ivanov <antivano@cisco.com> [rw: minor whitespace fixes] Signed-off-by: Richard Weinberger <richard@nod.at> 
The reverse case of this race (you must msync before read) is
well known. This is the not so common one.

It can be triggered only on systems which do a lot of task
switching and only at UML startup. If you are starting 200+ UMLs
~ 0.5% will always die without this fix.

Signed-off-by: Anton Ivanov <antivano@cisco.com>
[rw: minor whitespace fixes]
Signed-off-by: Richard Weinberger <richard@nod.at>
um: Missing pipe handling 2014-04-20T21:13:30+00:00 Anton Ivanov antivano@cisco.com 2014-03-07T18:37:46+00:00 9fcb663be42e4727c1beabc7c80e2d839199e6b1 UML does not handle sigpipe. As a result when running it under expect or redirecting the IO from the console to an external program it will crash if the program stops or exits. Signed-off-by: Anton Ivanov <antivano@cisco.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
UML does not handle sigpipe. As a result when running it under
expect or redirecting the IO from the console to an external program
it will crash if the program stops or exits.

Signed-off-by: Anton Ivanov <antivano@cisco.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
uml: Simplify tempdir logic. 2014-04-20T21:10:44+00:00 Tristan Schmelcher tschmelcher@google.com 2013-11-11T18:03:06+00:00 0d71832e3004a0833938cc28a096823cd55b8e79 Inferring the mount hierarchy correctly from /proc/mounts is hard when MS_MOVE may have been used, and the previous code did it wrongly. This change simplifies the logic to only require that /dev/shm be _on_ tmpfs (which can be checked trivially with statfs) rather than that it be a _mountpoint_ of tmpfs, since there isn't a compelling reason to be that strict. We also now check for tmpfs on whatever directory we ultimately use so that the user is better informed. This change also moves the more standard TMPDIR environment variable check ahead of the others. Applies to 3.12. Signed-off-by: Tristan Schmelcher <tschmelcher@google.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
Inferring the mount hierarchy correctly from /proc/mounts is hard when MS_MOVE
may have been used, and the previous code did it wrongly. This change simplifies
the logic to only require that /dev/shm be _on_ tmpfs (which can be checked
trivially with statfs) rather than that it be a _mountpoint_ of tmpfs, since
there isn't a compelling reason to be that strict. We also now check for tmpfs
on whatever directory we ultimately use so that the user is better informed.

This change also moves the more standard TMPDIR environment variable check ahead
of the others.

Applies to 3.12.

Signed-off-by: Tristan Schmelcher <tschmelcher@google.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: Make stack trace reliable against kernel mode faults 2013-11-17T10:27:30+00:00 Richard Weinberger richard@nod.at 2013-09-23T15:38:02+00:00 f72c22e45e8f8fe78c7f793d983bee5bed63497e As UML uses an alternative signal stack we cannot use the current stack pointer for stack dumping if UML itself dies by SIGSEGV. To bypass this issue we save regs taken from mcontext in our segv handler into thread_struct and use these regs to obtain the stack pointer in show_stack(). Signed-off-by: Richard Weinberger <richard@nod.at> 
As UML uses an alternative signal stack we cannot use
the current stack pointer for stack dumping if UML itself
dies by SIGSEGV. To bypass this issue we save regs taken
from mcontext in our segv handler into thread_struct and
use these regs to obtain the stack pointer in show_stack().

Signed-off-by: Richard Weinberger <richard@nod.at>
um: Run UML in it's own session. 2013-09-07T08:57:07+00:00 Richard Weinberger richard@nod.at 2013-08-18T11:30:09+00:00 250127216dd6635f5730752d7444bdec992aecb0 If UML is not run by a shell it can happen that UML will kill unrelated proceses upon a fatal exit because it issues a kill(0, ...). To prevent such oddities we create a new session in main(). Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
If UML is not run by a shell it can happen that UML
will kill unrelated proceses upon a fatal exit because
it issues a kill(0, ...).
To prevent such oddities we create a new session in main().

Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: Cleanup SIGTERM handling 2013-09-07T08:56:58+00:00 Richard Weinberger richard@nod.at 2013-08-18T11:30:08+00:00 91d44ff860a9e9c0db81a89cbc24fa31fbd8e6d3 Richard reported that some UML processes survive if the UML main process receives a SIGTERM. This issue was caused by a wrongly placed signal(SIGTERM, SIG_DFL) in init_new_thread_signals(). It disabled the UML exit handler accidently for some processes. The correct solution is to disable the fatal handler for all UML helper threads/processes. Such that last_ditch_exit() does not get called multiple times and all processes can exit due to SIGTERM. Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
Richard reported that some UML processes survive if the UML
main process receives a SIGTERM.
This issue was caused by a wrongly placed signal(SIGTERM, SIG_DFL)
in init_new_thread_signals().
It disabled the UML exit handler accidently for some processes.
The correct solution is to disable the fatal handler for all
UML helper threads/processes.
Such that last_ditch_exit() does not get called multiple times
and all processes can exit due to SIGTERM.

Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
um: ubd: Add REQ_FLUSH suppport 2013-09-07T08:56:49+00:00 Richard Weinberger richard@nod.at 2013-08-18T11:30:06+00:00 805f11a0d515658106bfbfadceff0eb30bd90ad2 UML's block device driver does not support write barriers, to support this this patch adds REQ_FLUSH suppport. Every time the block layer sends a REQ_FLUSH we fsync() now our backing file to guarantee data consistency. Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com> Signed-off-by: Richard Weinberger <richard@nod.at> 
UML's block device driver does not support write barriers,
to support this this patch adds REQ_FLUSH suppport.
Every time the block layer sends a REQ_FLUSH we fsync() now
our backing file to guarantee data consistency.

Reported-and-tested-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Richard Weinberger <richard@nod.at>