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x86/extable: Introduce _ASM_EXTABLE_UA for uaccess fixups

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Currently, most fixups for attempting to access userspace memory are
handled using _ASM_EXTABLE, which is also used for various other types of
fixups (e.g. safe MSR access, IRET failures, and a bunch of other things).
In order to make it possible to add special safety checks to uaccess fixups
(in particular, checking whether the fault address is actually in
userspace), introduce a new exception table handler ex_handler_uaccess()
and wire it up to all the user access fixups (excluding ones that
already use _ASM_EXTABLE_EX).

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: kernel-hardening@lists.openwall.com
Cc: dvyukov@google.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20180828201421.157735-5-jannh@google.com
This commit is contained in:
Jann Horn
2018-08-28 22:14:18 +02:00
committed by Thomas Gleixner
parent e3e4d5019c
commit 75045f77f7
12 changed files with 160 additions and 142 deletions
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4
arch/x86/lib/usercopy_64.c
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@@ -37,8 +37,8 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
"3: lea 0(%[size1],%[size8],8),%[size8]\n"
" jmp 2b\n"
".previous\n"
_ASM_EXTABLE(0b,3b)
_ASM_EXTABLE(1b,2b)
_ASM_EXTABLE_UA(0b, 3b)
_ASM_EXTABLE_UA(1b, 2b)
: [size8] "=&c"(size), [dst] "=&D" (__d0)
: [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr));
clac();