Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Sat, 5 Dec 2015 09:54:48 -0800 | From | tip-bot for Dave Hansen <> | Subject | [tip:x86/urgent] x86/mpx: Fix instruction decoder condition |
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Commit-ID: 8e8efe0379bd93e8219ca0fc6fa80b5dd85b09cb Gitweb: http://git.kernel.org/tip/8e8efe0379bd93e8219ca0fc6fa80b5dd85b09cb Author: Dave Hansen <dave.hansen@linux.intel.com> AuthorDate: Mon, 30 Nov 2015 16:31:13 -0800 Committer: Thomas Gleixner <tglx@linutronix.de> CommitDate: Sat, 5 Dec 2015 18:52:14 +0100
x86/mpx: Fix instruction decoder condition
MPX decodes instructions in order to tell which bounds register was violated. Part of this decoding involves looking at the "REX prefix" which is a special instrucion prefix used to retrofit support for new registers in to old instructions.
The X86_REX_*() macros are defined to return actual bit values:
#define X86_REX_R(rex) ((rex) & 4)
*not* boolean values. However, the MPX code was checking for them like they were booleans. This might have led to us mis-decoding the "REX prefix" and giving false information out to userspace about bounds violations. X86_REX_B() actually is bit 1, so this is really only broken for the X86_REX_X() case.
Fix the conditionals up to tolerate the non-boolean values.
Fixes: fcc7ffd67991 "x86, mpx: Decode MPX instruction to get bound violation information" Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: x86@kernel.org Cc: Dave Hansen <dave@sr71.net> Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20151201003113.D800C1E0@viggo.jf.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/mm/mpx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 1202d5c..b2fd67d 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -101,19 +101,19 @@ 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); - if (X86_REX_B(insn->rex_prefix.value) == 1) + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break; case REG_TYPE_INDEX: regno = X86_SIB_INDEX(insn->sib.value); - if (X86_REX_X(insn->rex_prefix.value) == 1) + if (X86_REX_X(insn->rex_prefix.value)) regno += 8; break; case REG_TYPE_BASE: regno = X86_SIB_BASE(insn->sib.value); - if (X86_REX_B(insn->rex_prefix.value) == 1) + if (X86_REX_B(insn->rex_prefix.value)) regno += 8; break;
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