linux.git/kernel/kexec.c, branch v5.10.258

panic, kexec: make __crash_kexec() NMI safe

2023-04-20T10:10:29+00:00

commit 05c6257433b7212f07a7e53479a8ab038fc1666a upstream.

Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI
panic() doesn't work.  The cause of that lies in the PREEMPT_RT definition
of mutex_trylock():

	if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task()))
		return 0;

This prevents an nmi_panic() from executing the main body of
__crash_kexec() which does the actual kexec into the kdump kernel.  The
warning and return are explained by:

  6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
  [...]
  The reasons for this are:

      1) There is a potential deadlock in the slowpath

      2) Another cpu which blocks on the rtmutex will boost the task
	 which allegedly locked the rtmutex, but that cannot work
	 because the hard/softirq context borrows the task context.

Furthermore, grabbing the lock isn't NMI safe, so do away with kexec_mutex
and replace it with an atomic variable.  This is somewhat overzealous as
*some* callsites could keep using a mutex (e.g.  the sysfs-facing ones
like crash_shrink_memory()), but this has the benefit of involving a
single unified lock and preventing any future NMI-related surprises.

Tested by triggering NMI panics via:

  $ echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi
  $ echo 1 > /proc/sys/kernel/unknown_nmi_panic
  $ echo 1 > /proc/sys/kernel/panic

  $ ipmitool power diag

Link: https://lkml.kernel.org/r/20220630223258.4144112-3-vschneid@redhat.com
Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context")
Signed-off-by: Valentin Schneider 
Cc: Arnd Bergmann 
Cc: Baoquan He 
Cc: "Eric W . Biederman" 
Cc: Juri Lelli 
Cc: Luis Claudio R. Goncalves 
Cc: Miaohe Lin 
Cc: Petr Mladek 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Wen Yang 
Signed-off-by: Greg Kroah-Hartman

kexec: move locking into do_kexec_load

2023-04-20T10:10:28+00:00

commit 4b692e861619353ce069e547a67c8d0e32d9ef3d upstream.

Patch series "compat: remove compat_alloc_user_space", v5.

Going through compat_alloc_user_space() to convert indirect system call
arguments tends to add complexity compared to handling the native and
compat logic in the same code.

This patch (of 6):

The locking is the same between the native and compat version of
sys_kexec_load(), so it can be done in the common implementation to reduce
duplication.

Link: https://lkml.kernel.org/r/20210727144859.4150043-1-arnd@kernel.org
Link: https://lkml.kernel.org/r/20210727144859.4150043-2-arnd@kernel.org
Signed-off-by: Arnd Bergmann 
Co-developed-by: Eric Biederman 
Co-developed-by: Christoph Hellwig 
Acked-by: "Eric W. Biederman" 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Thomas Bogendoerfer 
Cc: "James E.J. Bottomley" 
Cc: Helge Deller 
Cc: Michael Ellerman 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Heiko Carstens 
Cc: Vasily Gorbik 
Cc: Christian Borntraeger 
Cc: "David S. Miller" 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Borislav Petkov 
Cc: "H. Peter Anvin" 
Cc: Al Viro 
Cc: Feng Tang 
Cc: Christoph Hellwig 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Wen Yang 
Signed-off-by: Greg Kroah-Hartman

LSM: Introduce kernel_post_load_data() hook

2020-10-05T11:37:03+00:00

There are a few places in the kernel where LSMs would like to have
visibility into the contents of a kernel buffer that has been loaded or
read. While security_kernel_post_read_file() (which includes the
buffer) exists as a pairing for security_kernel_read_file(), no such
hook exists to pair with security_kernel_load_data().

Earlier proposals for just using security_kernel_post_read_file() with a
NULL file argument were rejected (i.e. "file" should always be valid for
the security_..._file hooks, but it appears at least one case was
left in the kernel during earlier refactoring. (This will be fixed in
a subsequent patch.)

Since not all cases of security_kernel_load_data() can have a single
contiguous buffer made available to the LSM hook (e.g. kexec image
segments are separately loaded), there needs to be a way for the LSM to
reason about its expectations of the hook coverage. In order to handle
this, add a "contents" argument to the "kernel_load_data" hook that
indicates if the newly added "kernel_post_load_data" hook will be called
with the full contents once loaded. That way, LSMs requiring full contents
can choose to unilaterally reject "kernel_load_data" with contents=false
(which is effectively the existing hook coverage), but when contents=true
they can allow it and later evaluate the "kernel_post_load_data" hook
once the buffer is loaded.

With this change, LSMs can gain coverage over non-file-backed data loads
(e.g. init_module(2) and firmware userspace helper), which will happen
in subsequent patches.

Additionally prepare IMA to start processing these cases.

Signed-off-by: Kees Cook 
Reviewed-by: KP Singh 
Link: https://lore.kernel.org/r/20201002173828.2099543-9-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman

kexec: add machine_kexec_post_load()

2020-01-08T16:32:55+00:00

It is the same as machine_kexec_prepare(), but is called after segments are
loaded. This way, can do processing work with already loaded relocation
segments. One such example is arm64: it has to have segments loaded in
order to create a page table, but it cannot do it during kexec time,
because at that time allocations won't be possible anymore.

Signed-off-by: Pavel Tatashin 
Acked-by: Dave Young 
Signed-off-by: Will Deacon

kexec_load: Disable at runtime if the kernel is locked down

2019-08-20T04:54:15+00:00

The kexec_load() syscall permits the loading and execution of arbitrary
code in ring 0, which is something that lock-down is meant to prevent. It
makes sense to disable kexec_load() in this situation.

This does not affect kexec_file_load() syscall which can check for a
signature on the image to be booted.

Signed-off-by: David Howells 
Signed-off-by: Matthew Garrett 
Acked-by: Dave Young 
Reviewed-by: Kees Cook 
cc: kexec@lists.infradead.org
Signed-off-by: James Morris

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 230

2019-06-19T15:09:06+00:00

Based on 2 normalized pattern(s):

  this source code is licensed under the gnu general public license
  version 2 see the file copying for more details

  this source code is licensed under general public license version 2
  see

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 52 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Enrico Weigelt 
Reviewed-by: Allison Randal 
Reviewed-by: Alexios Zavras 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190602204653.449021192@linutronix.de
Signed-off-by: Greg Kroah-Hartman

kexec: add call to LSM hook in original kexec_load syscall

2018-07-16T19:31:57+00:00

In order for LSMs and IMA-appraisal to differentiate between kexec_load
and kexec_file_load syscalls, both the original and new syscalls must
call an LSM hook.  This patch adds a call to security_kernel_load_data()
in the original kexec_load syscall.

Signed-off-by: Mimi Zohar 
Cc: Eric Biederman 
Cc: Kees Cook 
Acked-by: Serge Hallyn 
Acked-by: Kees Cook 
Signed-off-by: James Morris

kexec: call do_kexec_load() in compat syscall directly

2018-04-02T18:15:01+00:00

do_kexec_load() can be called directly by compat_sys_kexec() as long as
the same parameters checks are completed which are currently handled
(also) by sys_kexec(). Therefore, move those to kexec_load_check(),
call that newly introduced helper function from both sys_kexec() and
compat_sys_kexec(), and duplicate the remaining code from sys_kexec()
in compat_sys_kexec().

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Eric Biederman 
Cc: kexec@lists.infradead.org
Signed-off-by: Dominik Brodowski

kdump: protect vmcoreinfo data under the crash memory

2017-07-12T23:26:00+00:00

Currently vmcoreinfo data is updated at boot time subsys_initcall(), it
has the risk of being modified by some wrong code during system is
running.

As a result, vmcore dumped may contain the wrong vmcoreinfo.  Later on,
when using "crash", "makedumpfile", etc utility to parse this vmcore, we
probably will get "Segmentation fault" or other unexpected errors.

E.g.  1) wrong code overwrites vmcoreinfo_data; 2) further crashes the
system; 3) trigger kdump, then we obviously will fail to recognize the
crash context correctly due to the corrupted vmcoreinfo.

Now except for vmcoreinfo, all the crash data is well
protected(including the cpu note which is fully updated in the crash
path, thus its correctness is guaranteed).  Given that vmcoreinfo data
is a large chunk prepared for kdump, we better protect it as well.

To solve this, we relocate and copy vmcoreinfo_data to the crash memory
when kdump is loading via kexec syscalls.  Because the whole crash
memory will be protected by existing arch_kexec_protect_crashkres()
mechanism, we naturally protect vmcoreinfo_data from write(even read)
access under kernel direct mapping after kdump is loaded.

Since kdump is usually loaded at the very early stage after boot, we can
trust the correctness of the vmcoreinfo data copied.

On the other hand, we still need to operate the vmcoreinfo safe copy
when crash happens to generate vmcoreinfo_note again, we rely on vmap()
to map out a new kernel virtual address and update to use this new one
instead in the following crash_save_vmcoreinfo().

BTW, we do not touch vmcoreinfo_note, because it will be fully updated
using the protected vmcoreinfo_data after crash which is surely correct
just like the cpu crash note.

Link: http://lkml.kernel.org/r/1493281021-20737-3-git-send-email-xlpang@redhat.com
Signed-off-by: Xunlei Pang 
Tested-by: Michael Holzheu 
Cc: Benjamin Herrenschmidt 
Cc: Dave Young 
Cc: Eric Biederman 
Cc: Hari Bathini 
Cc: Juergen Gross 
Cc: Mahesh Salgaonkar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kexec: allow architectures to override boot mapping

2016-08-02T23:35:27+00:00

kexec physical addresses are the boot-time view of the system.  For
certain ARM systems (such as Keystone 2), the boot view of the system
does not match the kernel's view of the system: the boot view uses a
special alias in the lower 4GB of the physical address space.

To cater for these kinds of setups, we need to translate between the
boot view physical addresses and the normal kernel view physical
addresses.  This patch extracts the current transation points into
linux/kexec.h, and allows an architecture to override the functions.

Due to the translations required, we unfortunately end up with six
translation functions, which are reduced down to four that the
architecture can override.

[akpm@linux-foundation.org: kexec.h needs asm/io.h for phys_to_virt()]
Link: http://lkml.kernel.org/r/E1b8koP-0004HZ-Vf@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King 
Cc: Keerthy 
Cc: Pratyush Anand 
Cc: Vitaly Andrianov 
Cc: Eric Biederman 
Cc: Dave Young 
Cc: Baoquan He 
Cc: Vivek Goyal 
Cc: Simon Horman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds