lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 3 Mar 2017 13:41:15 -0800 From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> To: Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de> Cc: Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Brian Gerst <brgerst@...il.com>, Chris Metcalf <cmetcalf@...lanox.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Paolo Bonzini <pbonzini@...hat.com>, Liang Z Li <liang.z.li@...el.com>, Masami Hiramatsu <mhiramat@...nel.org>, Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>, Jonathan Corbet <corbet@....net>, "Michael S. Tsirkin" <mst@...hat.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Vlastimil Babka <vbabka@...e.cz>, Chen Yucong <slaoub@...il.com>, Alexandre Julliard <julliard@...ehq.org>, Stas Sergeev <stsp@...t.ru>, Fenghua Yu <fenghua.yu@...el.com>, "Ravi V. Shankar" <ravi.v.shankar@...el.com>, Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org, x86@...nel.org, linux-msdos@...r.kernel.org, wine-devel@...ehq.org, Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Adam Buchbinder <adam.buchbinder@...il.com>, Colin Ian King <colin.king@...onical.com>, Lorenzo Stoakes <lstoakes@...il.com>, Qiaowei Ren <qiaowei.ren@...el.com>, Nathan Howard <liverlint@...il.com>, Adan Hawthorn <adanhawthorn@...il.com>, Joe Perches <joe@...ches.com> Subject: [v5 03/20] x86/mpx: Do not use R/EBP as base in the SIB byte with Mod = 0 Section 2.2.1.2 of the Intel 64 and IA-32 Architectures Software Developer's Manual volume 2A states that when a SIB byte is used and the base of the SIB byte points to R/EBP (i.e., base = 5) and the mod part of the ModRM byte is zero, the value of such register will not be used as part of the address computation. To signal this, a -EDOM error is returned to indicate callers that they should ignore the value. Also, for this particular case, a displacement of 32-bits should follow the SIB byte if the mod part of ModRM is equal to zero. The instruction decoder ensures that this is the case. Cc: Dave Hansen <dave.hansen@...ux.intel.com> Cc: Adam Buchbinder <adam.buchbinder@...il.com> Cc: Colin Ian King <colin.king@...onical.com> Cc: Lorenzo Stoakes <lstoakes@...il.com> Cc: Qiaowei Ren <qiaowei.ren@...el.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Nathan Howard <liverlint@...il.com> Cc: Adan Hawthorn <adanhawthorn@...il.com> Cc: Joe Perches <joe@...ches.com> Cc: Ravi V. Shankar <ravi.v.shankar@...el.com> Cc: x86@...nel.org Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> --- arch/x86/mm/mpx.c | 29 ++++++++++++++++++++++------- 1 file changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index d9e92d6..ef7eb67 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -121,6 +121,17 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, case REG_TYPE_BASE: regno = X86_SIB_BASE(insn->sib.value); + /* + * If mod is 0 and register R/EBP (regno=5) is indicated in the + * base part of the SIB byte, the value of such register should + * not be used in the address computation. Also, a 32-bit + * displacement is expected in this case; the instruction + * decoder takes care of it. This is true for both R13 and + * R/EBP as REX.B will not be decoded. + */ + if (regno == 5 && X86_MODRM_MOD(insn->modrm.value) == 0) + return -EDOM; + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break; @@ -161,16 +172,21 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) eff_addr = regs_get_register(regs, addr_offset); } else { if (insn->sib.nbytes) { + /* + * Negative values in the base and index offset means + * an error when decoding the SIB byte. Except -EDOM, + * which means that the registers should not be used + * in the address computation. + */ base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); - if (base_offset < 0) + if (unlikely(base_offset == -EDOM)) + base = 0; + else if (unlikely(base_offset < 0)) goto out_err; + else + base = regs_get_register(regs, base_offset); indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); - /* - * A negative offset generally means a error, except - * -EDOM, which means that the contents of the register - * should not be used as index. - */ if (unlikely(indx_offset == -EDOM)) indx = 0; else if (unlikely(indx_offset < 0)) @@ -178,7 +194,6 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) else indx = regs_get_register(regs, indx_offset); - base = regs_get_register(regs, base_offset); eff_addr = base + indx * (1 << X86_SIB_SCALE(sib)); } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); -- 2.9.3
Powered by blists - more mailing lists