linux-stable.git/include/linux/kexec.h, branch v6.3.4

kexec: introduce sysctl parameters kexec_load_limit_*

2023-02-03T06:50:05+00:00

kexec allows replacing the current kernel with a different one.  This is
usually a source of concerns for sysadmins that want to harden a system.

Linux already provides a way to disable loading new kexec kernel via
kexec_load_disabled, but that control is very coard, it is all or nothing
and does not make distinction between a panic kexec and a normal kexec.

This patch introduces new sysctl parameters, with finer tuning to specify
how many times a kexec kernel can be loaded.  The sysadmin can set
different limits for kexec panic and kexec reboot kernels.  The value can
be modified at runtime via sysctl, but only with a stricter value.

With these new parameters on place, a system with loadpin and verity
enabled, using the following kernel parameters:
sysctl.kexec_load_limit_reboot=0 sysct.kexec_load_limit_panic=1 can have a
good warranty that if initrd tries to load a panic kernel, a malitious
user will have small chances to replace that kernel with a different one,
even if they can trigger timeouts on the disk where the panic kernel
lives.

Link: https://lkml.kernel.org/r/20221114-disable-kexec-reset-v6-3-6a8531a09b9a@chromium.org
Signed-off-by: Ricardo Ribalda 
Reviewed-by: Steven Rostedt (Google) 
Acked-by: Baoquan He 
Cc: Bagas Sanjaya 
Cc: "Eric W. Biederman" 
Cc: Guilherme G. Piccoli  # Steam Deck
Cc: Joel Fernandes (Google) 
Cc: Jonathan Corbet 
Cc: Philipp Rudo 
Cc: Ross Zwisler 
Cc: Sergey Senozhatsky 
Signed-off-by: Andrew Morton

kexec: factor out kexec_load_permitted

2023-02-03T06:50:04+00:00

Both syscalls (kexec and kexec_file) do the same check, let's factor it
out.

Link: https://lkml.kernel.org/r/20221114-disable-kexec-reset-v6-2-6a8531a09b9a@chromium.org
Signed-off-by: Ricardo Ribalda 
Reviewed-by: Steven Rostedt (Google) 
Acked-by: Baoquan He 
Cc: Bagas Sanjaya 
Cc: "Eric W. Biederman" 
Cc: Guilherme G. Piccoli 
Cc: Joel Fernandes (Google) 
Cc: Jonathan Corbet 
Cc: Philipp Rudo 
Cc: Ross Zwisler 
Cc: Sergey Senozhatsky 
Signed-off-by: Andrew Morton

kexec: replace crash_mem_range with range

2022-11-18T21:55:07+00:00

We already have struct range, so just use it.

Link: https://lkml.kernel.org/r/20220929042936.22012-4-bhe@redhat.com
Signed-off-by: Li Chen 
Signed-off-by: Baoquan He 
Acked-by: Baoquan He 
Cc: Michael Ellerman 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Chen Lifu 
Cc: "Eric W . Biederman" 
Cc: Jianglei Nie 
Cc: Petr Mladek 
Cc: Russell King 
Cc: ye xingchen 
Cc: Zeal Robot 
Signed-off-by: Andrew Morton

kexec: turn all kexec_mutex acquisitions into trylocks

2022-09-12T04:55:06+00:00

Patch series "kexec, panic: Making crash_kexec() NMI safe", v4.


This patch (of 2):

Most acquistions of kexec_mutex are done via mutex_trylock() - those were
a direct "translation" from:

  8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()")

there have however been two additions since then that use mutex_lock():
crash_get_memory_size() and crash_shrink_memory().

A later commit will replace said mutex with an atomic variable, and
locking operations will become atomic_cmpxchg().  Rather than having those
mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into
trylocks that can return -EBUSY on acquisition failure.

This does halve the printable size of the crash kernel, but that's still
neighbouring 2G for 32bit kernels which should be ample enough.

Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com
Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com
Signed-off-by: Valentin Schneider 
Cc: Arnd Bergmann 
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 
Cc: Baoquan He 
Signed-off-by: Andrew Morton

kexec, KEYS: make the code in bzImage64_verify_sig generic

2022-07-15T16:21:16+00:00

commit 278311e417be ("kexec, KEYS: Make use of platform keyring for
signature verify") adds platform keyring support on x86 kexec but not
arm64.

The code in bzImage64_verify_sig uses the keys on the
.builtin_trusted_keys, .machine, if configured and enabled,
.secondary_trusted_keys, also if configured, and .platform keyrings
to verify the signed kernel image as PE file.

Cc: kexec@lists.infradead.org
Cc: keyrings@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Reviewed-by: Michal Suchanek 
Signed-off-by: Coiby Xu 
Signed-off-by: Mimi Zohar

kexec: clean up arch_kexec_kernel_verify_sig

2022-07-15T16:21:16+00:00

Before commit 105e10e2cf1c ("kexec_file: drop weak attribute from
functions"), there was already no arch-specific implementation
of arch_kexec_kernel_verify_sig. With weak attribute dropped by that
commit, arch_kexec_kernel_verify_sig is completely useless. So clean it
up.

Note later patches are dependent on this patch so it should be backported
to the stable tree as well.

Cc: stable@vger.kernel.org
Suggested-by: Eric W. Biederman 
Reviewed-by: Michal Suchanek 
Acked-by: Baoquan He 
Signed-off-by: Coiby Xu 
[zohar@linux.ibm.com: reworded patch description "Note"]
Link: https://lore.kernel.org/linux-integrity/20220714134027.394370-1-coxu@redhat.com/
Signed-off-by: Mimi Zohar

kexec: drop weak attribute from functions

2022-07-15T16:21:16+00:00

Drop __weak attribute from functions in kexec_core.c:
- machine_kexec_post_load()
- arch_kexec_protect_crashkres()
- arch_kexec_unprotect_crashkres()
- crash_free_reserved_phys_range()

Link: https://lkml.kernel.org/r/c0f6219e03cb399d166d518ab505095218a902dd.1656659357.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Naveen N. Rao 
Suggested-by: Eric Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Mimi Zohar

kexec_file: drop weak attribute from functions

2022-07-15T16:21:16+00:00

As requested
(http://lkml.kernel.org/r/87ee0q7b92.fsf@email.froward.int.ebiederm.org),
this series converts weak functions in kexec to use the #ifdef approach.

Quoting the 3e35142ef99fe ("kexec_file: drop weak attribute from
arch_kexec_apply_relocations[_add]") changelog:

: Since commit d1bcae833b32f1 ("ELF: Don't generate unused section symbols")
: [1], binutils (v2.36+) started dropping section symbols that it thought
: were unused.  This isn't an issue in general, but with kexec_file.c, gcc
: is placing kexec_arch_apply_relocations[_add] into a separate
: .text.unlikely section and the section symbol ".text.unlikely" is being
: dropped.  Due to this, recordmcount is unable to find a non-weak symbol in
: .text.unlikely to generate a relocation record against.

This patch (of 2);

Drop __weak attribute from functions in kexec_file.c:
- arch_kexec_kernel_image_probe()
- arch_kimage_file_post_load_cleanup()
- arch_kexec_kernel_image_load()
- arch_kexec_locate_mem_hole()
- arch_kexec_kernel_verify_sig()

arch_kexec_kernel_image_load() calls into kexec_image_load_default(), so
drop the static attribute for the latter.

arch_kexec_kernel_verify_sig() is not overridden by any architecture, so
drop the __weak attribute.

Link: https://lkml.kernel.org/r/cover.1656659357.git.naveen.n.rao@linux.vnet.ibm.com
Link: https://lkml.kernel.org/r/2cd7ca1fe4d6bb6ca38e3283c717878388ed6788.1656659357.git.naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Naveen N. Rao 
Suggested-by: Eric Biederman 
Signed-off-by: Andrew Morton 
Signed-off-by: Mimi Zohar

ima: force signature verification when CONFIG_KEXEC_SIG is configured

2022-07-13T14:13:41+00:00

Currently, an unsigned kernel could be kexec'ed when IMA arch specific
policy is configured unless lockdown is enabled. Enforce kernel
signature verification check in the kexec_file_load syscall when IMA
arch specific policy is configured.

Fixes: 99d5cadfde2b ("kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE")
Reported-and-suggested-by: Mimi Zohar 
Signed-off-by: Coiby Xu 
Signed-off-by: Mimi Zohar

Merge tag 'riscv-for-linus-5.19-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

2022-05-31T21:10:54+00:00

Pull RISC-V updates from Palmer Dabbelt:

 - Support for the Svpbmt extension, which allows memory attributes to
   be encoded in pages

 - Support for the Allwinner D1's implementation of page-based memory
   attributes

 - Support for running rv32 binaries on rv64 systems, via the compat
   subsystem

 - Support for kexec_file()

 - Support for the new generic ticket-based spinlocks, which allows us
   to also move to qrwlock. These should have already gone in through
   the asm-geneic tree as well

 - A handful of cleanups and fixes, include some larger ones around
   atomics and XIP

* tag 'riscv-for-linus-5.19-mw0' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux: (51 commits)
  RISC-V: Prepare dropping week attribute from arch_kexec_apply_relocations[_add]
  riscv: compat: Using seperated vdso_maps for compat_vdso_info
  RISC-V: Fix the XIP build
  RISC-V: Split out the XIP fixups into their own file
  RISC-V: ignore xipImage
  RISC-V: Avoid empty create_*_mapping definitions
  riscv: Don't output a bogus mmu-type on a no MMU kernel
  riscv: atomic: Add custom conditional atomic operation implementation
  riscv: atomic: Optimize dec_if_positive functions
  riscv: atomic: Cleanup unnecessary definition
  RISC-V: Load purgatory in kexec_file
  RISC-V: Add purgatory
  RISC-V: Support for kexec_file on panic
  RISC-V: Add kexec_file support
  RISC-V: use memcpy for kexec_file mode
  kexec_file: Fix kexec_file.c build error for riscv platform
  riscv: compat: Add COMPAT Kbuild skeletal support
  riscv: compat: ptrace: Add compat_arch_ptrace implement
  riscv: compat: signal: Add rt_frame implementation
  riscv: add memory-type errata for T-Head
  ...