Messages in this thread Patch in this message |  | | Date | Tue, 29 Aug 2017 18:09:06 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v8 05/28] x86/mpx: Use signed variables to compute effective addresses |
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On Fri, Aug 18, 2017 at 05:27:46PM -0700, Ricardo Neri wrote: > Even though memory addresses are unsigned, the operands used to compute the > effective address do have a sign. This is true for ModRM.rm, SIB.base, > SIB.index as well as the displacement bytes. Thus, signed variables shall > be used when computing the effective address from these operands. Once the > signed effective address has been computed, it is casted to an unsigned > long to determine the linear address. > > Variables are renamed to better reflect the type of address being > computed. > > Cc: Borislav Petkov <bp@suse.de> > Cc: Andy Lutomirski <luto@kernel.org> > 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: Peter Zijlstra <peterz@infradead.org> > Cc: Nathan Howard <liverlint@gmail.com> > Cc: Adan Hawthorn <adanhawthorn@gmail.com> > Cc: Joe Perches <joe@perches.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/mm/mpx.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-)
I think you can simplify this function even more (diff ontop):
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 9eec98022510..d0ec5c9b2a57 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -139,7 +139,7 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs, static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) { int addr_offset, base_offset, indx_offset; - unsigned long linear_addr; + unsigned long linear_addr = -1; long eff_addr, base, indx; insn_byte_t sib; @@ -150,18 +150,18 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) if (X86_MODRM_MOD(insn->modrm.value) == 3) { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) - goto out_err; + goto out; eff_addr = regs_get_register(regs, addr_offset); } else { if (insn->sib.nbytes) { base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE); if (base_offset < 0) - goto out_err; + goto out; indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX); if (indx_offset < 0) - goto out_err; + goto out; base = regs_get_register(regs, base_offset); indx = regs_get_register(regs, indx_offset); @@ -170,7 +170,7 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) } else { addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM); if (addr_offset < 0) - goto out_err; + goto out; eff_addr = regs_get_register(regs, addr_offset); } @@ -180,9 +180,8 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs) linear_addr = (unsigned long)eff_addr; +out: return (void __user *)linear_addr; -out_err: - return (void __user *)-1; } static int mpx_insn_decode(struct insn *insn, -- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
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