Commit 86cc3510 authored Nov 05, 2017 by Ricardo Neri Committed by Ingo Molnar Nov 08, 2017

x86/insn-eval: Handle 32-bit address encodings in virtual-8086 mode



It is possible to utilize 32-bit address encodings in virtual-8086 mode via
an address override instruction prefix. However, the range of the
effective address is still limited to [0x-0xffff]. In such a case, return
error.

Also, linear addresses in virtual-8086 mode are limited to 20 bits. Enforce
such limit by truncating the most significant bytes of the computed linear
address.

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qiaowei Ren <qiaowei.ren@intel.com>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: ricardo.neri@intel.com
Link: http://lkml.kernel.org/r/1509935277-22138-5-git-send-email-ricardo.neri-calderon@linux.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent cd9b594a

arch/x86/lib/insn-eval.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -1041,6 +1041,13 @@ static void __user get_addr_ref_32(struct insn insn, struct pt_regs *regs)
		if (!user_64bit_mode(regs) && ((unsigned int)eff_addr > seg_limit))
		goto out;

		/*
		* Even though 32-bit address encodings are allowed in virtual-8086
		* mode, the address range is still limited to [0x-0xffff].
		*/
		if (v8086_mode(regs) && (eff_addr & ~0xffff))
		goto out;

		/*
		* Data type long could be 64 bits in size. Ensure that our 32-bit
		* effective address is not sign-extended when computing the linear
		@@ -1048,6 +1055,10 @@ static void __user get_addr_ref_32(struct insn insn, struct pt_regs *regs)
		*/
		linear_addr = (unsigned long)(eff_addr & 0xffffffff) + seg_base;

		/* Limit linear address to 20 bits */
		if (v8086_mode(regs))
		linear_addr &= 0xfffff;

		out:
		return (void __user *)linear_addr;
		}

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