3.19.8-ckt12 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> commit 8e8efe0379bd93e8219ca0fc6fa80b5dd85b09cb upstream. 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@xxxxxxxxxx> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: Dave Hansen <dave@xxxxxxxx> Link: http://lkml.kernel.org/r/20151201003113.D800C1E0@xxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- 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 3df5f1a..feda8ca 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -120,19 +120,19 @@ 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; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html