Commit-ID: e526a302e425ab11111efc5f59e52449bbcc768e Gitweb: https://git.kernel.org/tip/e526a302e425ab11111efc5f59e52449bbcc768e Author: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> AuthorDate: Fri, 27 Oct 2017 13:25:44 -0700 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Wed, 1 Nov 2017 21:50:13 +0100 x86/insn-eval: Indicate a 32-bit displacement if ModRM.mod is 0 and ModRM.rm is 101b Section 2.2.1.3 of the Intel 64 and IA-32 Architectures Software Developer's Manual volume 2A states that when ModRM.mod is zero and ModRM.rm is 101b, a 32-bit displacement follows the ModRM byte. This means that none of the registers are used in the computation of the effective address. A return value of -EDOM indicates callers that they should not use the value of registers when computing the effective address for the instruction. In long mode, the effective address is given by the 32-bit displacement plus the location of the next instruction. In protected mode, only the displacement is used. The instruction decoder takes care of obtaining the displacement. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Borislav Petkov <bp@xxxxxxx> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: ricardo.neri@xxxxxxxxx Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx> Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> Cc: Huang Rui <ray.huang@xxxxxxx> Cc: Qiaowei Ren <qiaowei.ren@xxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Jiri Slaby <jslaby@xxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx> Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx> Cc: Chen Yucong <slaoub@xxxxxxxxx> Cc: Adam Buchbinder <adam.buchbinder@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Thomas Garnier <thgarnie@xxxxxxxxxx> Link: https://lkml.kernel.org/r/1509135945-13762-18-git-send-email-ricardo.neri-calderon@xxxxxxxxxxxxxxx --- arch/x86/lib/insn-eval.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index 01e36bd..6bf819f 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -427,6 +427,14 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, switch (type) { case REG_TYPE_RM: regno = X86_MODRM_RM(insn->modrm.value); + + /* + * ModRM.mod == 0 and ModRM.rm == 5 means a 32-bit displacement + * follows the ModRM byte. + */ + if (!X86_MODRM_MOD(insn->modrm.value) && regno == 5) + return -EDOM; + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break; @@ -770,10 +778,21 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); - if (addr_offset < 0) + /* + * -EDOM means that we must ignore the address_offset. + * In such a case, in 64-bit mode the effective address + * relative to the RIP of the following instruction. + */ + if (addr_offset == -EDOM) { + if (user_64bit_mode(regs)) + eff_addr = (long)regs->ip + insn->length; + else + eff_addr = 0; + } else if (addr_offset < 0) { goto out; - - eff_addr = regs_get_register(regs, addr_offset); + } else { + eff_addr = regs_get_register(regs, addr_offset); + } } eff_addr += insn->displacement.value; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html