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Filename Latest commit message Latest commit date
Peter Zijlstra ecc6061038 x86/alternatives: Fix int3_emulate_call() selftest stack corruption
KASAN shows the following splat during boot:

  BUG: KASAN: unknown-crash in unwind_next_frame+0x3f6/0x490
  Read of size 8 at addr ffffffff84007db0 by task swapper/0

  CPU: 0 PID: 0 Comm: swapper Tainted: G                T 5.2.0-rc6-00013-g7457c0d #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
  Call Trace:
   dump_stack+0x19/0x1b
   print_address_description+0x1b0/0x2b2
   __kasan_report+0x10f/0x171
   kasan_report+0x12/0x1c
   __asan_load8+0x54/0x81
   unwind_next_frame+0x3f6/0x490
   unwind_next_frame+0x1b/0x23
   arch_stack_walk+0x68/0xa5
   stack_trace_save+0x7b/0xa0
   save_trace+0x3c/0x93
   mark_lock+0x1ef/0x9b1
   lock_acquire+0x122/0x221
   __mutex_lock+0xb6/0x731
   mutex_lock_nested+0x16/0x18
   _vm_unmap_aliases+0x141/0x183
   vm_unmap_aliases+0x14/0x16
   change_page_attr_set_clr+0x15e/0x2f2
   set_memory_4k+0x2a/0x2c
   check_bugs+0x11fd/0x1298
   start_kernel+0x793/0x7eb
   x86_64_start_reservations+0x55/0x76
   x86_64_start_kernel+0x87/0xaa
   secondary_startup_64+0xa4/0xb0

  Memory state around the buggy address:
   ffffffff84007c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1
   ffffffff84007d00: f1 00 00 00 00 00 00 00 00 00 f2 f2 f2 f3 f3 f3
  >ffffffff84007d80: f3 79 be 52 49 79 be 00 00 00 00 00 00 00 00 f1

It turns out that int3_selftest() is corrupting the stack.  The problem is
that the KASAN-ified version of int3_magic() is much less trivial than the
C code appears.  It clobbers several unexpected registers.  So when the
selftest's INT3 is converted to an emulated call to int3_magic(), the
registers are clobbered and Bad Things happen when the function returns.

Fix this by converting int3_magic() to the trivial ASM function it should
be, avoiding all calling convention issues. Also add ASM_CALL_CONSTRAINT to
the INT3 ASM, since it contains a 'CALL'.

[peterz: cribbed changelog from josh]

Fixes: 7457c0da02 ("x86/alternatives: Add int3_emulate_call() selftest")
Reported-by: kernel test robot <rong.a.chen@intel.com>
Debugged-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20190709125744.GB3402@hirez.programming.kicks-ass.net
2019-07-09 22:39:15 +02:00
arch x86/alternatives: Fix int3_emulate_call() selftest stack corruption 2019-07-09 22:39:15 +02:00
block blk-mq: fix up placement of debugfs directory of queue files 2019-07-06 10:07:38 -06:00
certs
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2019-07-05 13:31:19 +09:00
Documentation Merge branch 'x86-topology-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 18:28:44 -07:00
drivers Merge branch 'x86-topology-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 18:28:44 -07:00
fs Merge branch 'x86-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 17:28:57 -07:00
include Merge branch 'x86-topology-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 18:28:44 -07:00
init Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:39:53 -07:00
ipc
kernel Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:39:53 -07:00
lib Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:39:53 -07:00
LICENSES
mm arm64 updates for 5.3: 2019-07-08 09:54:55 -07:00
net Two more quick bugfixes for nfsd, fixing a regression causing mount 2019-07-05 19:00:37 -07:00
samples Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:39:53 -07:00
scripts Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:12:03 -07:00
security Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:12:03 -07:00
sound sound fixes for 5.2 2019-07-05 02:03:50 +09:00
tools Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 15:45:14 -07:00
usr
virt SPDX update for 5.2-rc6 2019-06-21 09:58:42 -07:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 11:59:59 -07:00
Makefile Linux 5.2 2019-07-07 15:41:56 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.