092b31aa20
All copy_to_user() implementations need to be prepared to handle faults
accessing userspace. The __memcpy_mcsafe() implementation handles both
mmu-faults on the user destination and machine-check-exceptions on the
source buffer. However, the memcpy_mcsafe() wrapper may silently
fallback to memcpy() depending on build options and cpu-capabilities.
Force copy_to_user_mcsafe() to always use __memcpy_mcsafe() when
available, and otherwise disable all of the copy_to_user_mcsafe()
infrastructure when __memcpy_mcsafe() is not available, i.e.
CONFIG_X86_MCE=n.
This fixes crashes of the form:
run fstests generic/323 at 2018-07-02 12:46:23
BUG: unable to handle kernel paging request at 00007f0d50001000
RIP: 0010:__memcpy+0x12/0x20
[..]
Call Trace:
copyout_mcsafe+0x3a/0x50
_copy_to_iter_mcsafe+0xa1/0x4a0
? dax_alive+0x30/0x50
dax_iomap_actor+0x1f9/0x280
? dax_iomap_rw+0x100/0x100
iomap_apply+0xba/0x130
? dax_iomap_rw+0x100/0x100
dax_iomap_rw+0x95/0x100
? dax_iomap_rw+0x100/0x100
xfs_file_dax_read+0x7b/0x1d0 [xfs]
xfs_file_read_iter+0xa7/0xc0 [xfs]
aio_read+0x11c/0x1a0
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
Link: http://lkml.kernel.org/r/153108277790.37979.1486841789275803399.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.