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Message-ID: <20151007111038.GC5046@nazgul.tnic> Date: Wed, 7 Oct 2015 13:10:38 +0200 From: Borislav Petkov <bp@...en8.de> To: Andy Lutomirski <luto@...nel.org> Cc: x86@...nel.org, linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>, Denys Vlasenko <dvlasenk@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH v2 05/36] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access On Mon, Oct 05, 2015 at 05:47:53PM -0700, Andy Lutomirski wrote: > Clearing NT is part of the prologue, whereas loading up arg6 makes > more sense to think about as part of syscall processing. Reorder > them. > > Signed-off-by: Andy Lutomirski <luto@...nel.org> > --- > arch/x86/entry/entry_64_compat.S | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S > index a9360d40fb7f..aa76864a8a6b 100644 > --- a/arch/x86/entry/entry_64_compat.S > +++ b/arch/x86/entry/entry_64_compat.S > @@ -89,15 +89,6 @@ ENTRY(entry_SYSENTER_compat) > sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */ > > /* > - * no need to do an access_ok check here because rbp has been > - * 32-bit zero extended > - */ > - ASM_STAC > -1: movl (%rbp), %ebp > - _ASM_EXTABLE(1b, ia32_badarg) > - ASM_CLAC > - > - /* > * Sysenter doesn't filter flags, so we need to clear NT > * ourselves. To save a few cycles, we can check whether > * NT was set instead of doing an unconditional popfq. > @@ -106,6 +97,15 @@ ENTRY(entry_SYSENTER_compat) > jnz sysenter_fix_flags > sysenter_flags_fixed: Btw, do I see it correctly that we can save us this jumping to sysenter_fix_flags and back to sysenter_flags_fixed? Label is jumped to only once and the couple of insns there can be behind a JZ... -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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