Revision 90c1cba2b3b3851c151229f61801919b2904d437 authored by Bart Van Assche on 03 April 2019, 23:35:52 UTC, committed by Ingo Molnar on 10 April 2019, 11:45:59 UTC
The following commit:

  a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use")

changed the behavior of lockdep_free_key_range() from
unconditionally zapping lock classes into only zapping lock classes if
debug_lock == true. Not zapping lock classes if debug_lock == false leaves
dangling pointers in several lockdep datastructures, e.g. lock_class::name
in the all_lock_classes list.

The shell command "cat /proc/lockdep" causes the kernel to iterate the
all_lock_classes list. Hence the "unable to handle kernel paging request" cash
that Shenghui encountered by running cat /proc/lockdep.

Since the new behavior can cause cat /proc/lockdep to crash, restore the
pre-v5.1 behavior.

This patch avoids that cat /proc/lockdep triggers the following crash
with debug_lock == false:

  BUG: unable to handle kernel paging request at fffffbfff40ca448
  RIP: 0010:__asan_load1+0x28/0x50
  Call Trace:
   string+0xac/0x180
   vsnprintf+0x23e/0x820
   seq_vprintf+0x82/0xc0
   seq_printf+0x92/0xb0
   print_name+0x34/0xb0
   l_show+0x184/0x200
   seq_read+0x59e/0x6c0
   proc_reg_read+0x11f/0x170
   __vfs_read+0x4d/0x90
   vfs_read+0xc5/0x1f0
   ksys_read+0xab/0x130
   __x64_sys_read+0x43/0x50
   do_syscall_64+0x71/0x210
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reported-by: shenghui <shhuiw@foxmail.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
Link: https://lkml.kernel.org/r/20190403233552.124673-1-bvanassche@acm.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1 parent 771acc7
Raw File
Kconfig
menuconfig SAMPLES
	bool "Sample kernel code"
	depends on !UML
	help
	  You can build and test sample kernel code here.

if SAMPLES

config SAMPLE_TRACE_EVENTS
	tristate "Build trace_events examples -- loadable modules only"
	depends on EVENT_TRACING && m
	help
	  This build trace event example modules.

config SAMPLE_TRACE_PRINTK
        tristate "Build trace_printk module - tests various trace_printk formats"
	depends on EVENT_TRACING && m
	help
	 This builds a module that calls trace_printk() and can be used to
	 test various trace_printk() calls from a module.

config SAMPLE_KOBJECT
	tristate "Build kobject examples -- loadable modules only"
	depends on m
	help
	  This config option will allow you to build a number of
	  different kobject sample modules showing how to use kobjects,
	  ksets, and ktypes properly.

	  If in doubt, say "N" here.

config SAMPLE_KPROBES
	tristate "Build kprobes examples -- loadable modules only"
	depends on KPROBES && m
	help
	  This build several kprobes example modules.

config SAMPLE_KRETPROBES
	tristate "Build kretprobes example -- loadable modules only"
	default m
	depends on SAMPLE_KPROBES && KRETPROBES

config SAMPLE_HW_BREAKPOINT
	tristate "Build kernel hardware breakpoint examples -- loadable module only"
	depends on HAVE_HW_BREAKPOINT && m
	help
	  This builds kernel hardware breakpoint example modules.

config SAMPLE_KFIFO
	tristate "Build kfifo examples -- loadable modules only"
	depends on m
	help
	  This config option will allow you to build a number of
	  different kfifo sample modules showing how to use the
	  generic kfifo API.

	  If in doubt, say "N" here.

config SAMPLE_KDB
	tristate "Build kdb command example -- loadable modules only"
	depends on KGDB_KDB && m
	help
	  Build an example of how to dynamically add the hello
	  command to the kdb shell.

config SAMPLE_QMI_CLIENT
	tristate "Build qmi client sample -- loadable modules only"
	depends on m
	depends on ARCH_QCOM
	depends on NET
	select QCOM_QMI_HELPERS
	help
	  Build an QMI client sample driver, which demonstrates how to
	  communicate with a remote QRTR service, using QMI encoded messages.

config SAMPLE_RPMSG_CLIENT
	tristate "Build rpmsg client sample -- loadable modules only"
	depends on RPMSG && m
	help
	  Build an rpmsg client sample driver, which demonstrates how
	  to communicate with an AMP-configured remote processor over
	  the rpmsg bus.

config SAMPLE_LIVEPATCH
	tristate "Build live patching samples -- loadable modules only"
	depends on LIVEPATCH && m
	help
	  Build sample live patch demonstrations.

config SAMPLE_CONFIGFS
	tristate "Build configfs patching sample -- loadable modules only"
	depends on CONFIGFS_FS && m
	help
	  Builds a sample configfs interface.

config SAMPLE_CONNECTOR
	tristate "Build connector sample -- loadable modules only"
	depends on CONNECTOR && m
	help
	  When enabled, this builds both a sample kernel module for
	  the connector interface and a user space tool to communicate
	  with it.
	  See also Documentation/connector/connector.txt

config SAMPLE_SECCOMP
	tristate "Build seccomp sample code -- loadable modules only"
	depends on SECCOMP_FILTER && m
	help
	  Build samples of seccomp filters using various methods of
	  BPF filter construction.

config SAMPLE_VFIO_MDEV_MTTY
	tristate "Build VFIO mtty example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	help
	  Build a virtual tty sample driver for use as a VFIO
	  mediated device

config SAMPLE_VFIO_MDEV_MDPY
	tristate "Build VFIO mdpy example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	help
	  Build a virtual display sample driver for use as a VFIO
	  mediated device.  It is a simple framebuffer and supports
	  the region display interface (VFIO_GFX_PLANE_TYPE_REGION).

config SAMPLE_VFIO_MDEV_MDPY_FB
	tristate "Build VFIO mdpy example guest fbdev driver -- loadable module only"
	depends on FB && m
	select FB_CFB_FILLRECT
	select FB_CFB_COPYAREA
	select FB_CFB_IMAGEBLIT
	help
	  Guest fbdev driver for the virtual display sample driver.

config SAMPLE_VFIO_MDEV_MBOCHS
	tristate "Build VFIO mdpy example mediated device sample code -- loadable modules only"
	depends on VFIO_MDEV_DEVICE && m
	select DMA_SHARED_BUFFER
	help
	  Build a virtual display sample driver for use as a VFIO
	  mediated device.  It supports the region display interface
	  (VFIO_GFX_PLANE_TYPE_DMABUF).
	  Emulate enough of qemu stdvga to make bochs-drm.ko happy.
	  That is basically the vram memory bar and the bochs dispi
	  interface vbe registers in the mmio register bar.
	  Specifically it does *not* include any legacy vga stuff.
	  Device looks a lot like "qemu -device secondary-vga".

config SAMPLE_ANDROID_BINDERFS
	bool "Build Android binderfs example"
	depends on CONFIG_ANDROID_BINDERFS
	help
	  Builds a sample program to illustrate the use of the Android binderfs
	  filesystem.

config SAMPLE_STATX
	bool "Build example extended-stat using code"
	depends on BROKEN
	help
	  Build example userspace program to use the new extended-stat syscall.

endif # SAMPLES
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