diff options
| author | Dan Williams <dan.j.williams@intel.com> | 2018-07-08 23:46:17 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-07-16 01:05:05 +0300 |
| commit | 092b31aa2048cf7561a39697974adcd147fbb27b (patch) | |
| tree | 2bd31cfd50215cff112d65ce0ff7e5b80025f259 | |
| parent | ca146f6f091e47b3fd18d6a7e76ec0297d202e0f (diff) | |
| download | linux-092b31aa2048cf7561a39697974adcd147fbb27b.tar.xz | |
x86/asm/memcpy_mcsafe: Fix copy_to_user_mcsafe() exception handling
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>
| -rw-r--r-- | arch/x86/Kconfig | 2 | ||||
| -rw-r--r-- | arch/x86/include/asm/uaccess_64.h | 7 |
2 files changed, 7 insertions, 2 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index f1dbb4ee19d7..887d3a7bb646 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -63,7 +63,7 @@ config X86 select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_REFCOUNT select ARCH_HAS_UACCESS_FLUSHCACHE if X86_64 - select ARCH_HAS_UACCESS_MCSAFE if X86_64 + select ARCH_HAS_UACCESS_MCSAFE if X86_64 && X86_MCE select ARCH_HAS_SET_MEMORY select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index 62acb613114b..a9d637bc301d 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -52,7 +52,12 @@ copy_to_user_mcsafe(void *to, const void *from, unsigned len) unsigned long ret; __uaccess_begin(); - ret = memcpy_mcsafe(to, from, len); + /* + * Note, __memcpy_mcsafe() is explicitly used since it can + * handle exceptions / faults. memcpy_mcsafe() may fall back to + * memcpy() which lacks this handling. + */ + ret = __memcpy_mcsafe(to, from, len); __uaccess_end(); return ret; } |