Messages in this thread Patch in this message |  | | From | Ricardo Neri <> | Subject | [PATCH v8 20/28] x86/insn-eval: Handle 32-bit address encodings in virtual-8086 mode | Date | Fri, 18 Aug 2017 17:28:01 -0700 |
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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.
Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Adam Buchbinder <adam.buchbinder@gmail.com> Cc: Colin Ian King <colin.king@canonical.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Cc: Qiaowei Ren <qiaowei.ren@intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Kees Cook <keescook@chromium.org> Cc: Thomas Garnier <thgarnie@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@suse.de> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: x86@kernel.org Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> --- arch/x86/lib/insn-eval.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 6537b613d0b3..93a6d1f57c2d 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -801,12 +801,23 @@ static void __user *get_addr_ref_32(struct insn *insn, struct pt_regs *regs) goto out_err; /* + * 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_err; + + /* * Data type long could be 64 bits in size. Ensure that our 32-bit * effective address is not sign-extended when computing the linear * address. */ linear_addr = (unsigned long)(eff_addr & 0xffffffff) + seg_base_addr; + /* Limit linear address to 20 bits */ + if (v8086_mode(regs)) + linear_addr &= 0xfffff; + return (void __user *)linear_addr; out_err: return (void __user *)-1L; -- 2.13.0
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