From dd27f998f0ed3c797032a82033fa191be7c61e4c Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 5 Oct 2015 17:47:53 -0700 Subject: [PATCH] x86/entry/64/compat: Fix SYSENTER's NT flag before user memory access 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 Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/19eb235828b2d2a52c53459e09f2974e15e65a35.1444091584.git.luto@kernel.org Signed-off-by: Ingo Molnar --- 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..e2cca89c1ed3 100644 --- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -88,15 +88,6 @@ ENTRY(entry_SYSENTER_compat) cld 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 @@ -106,6 +97,15 @@ ENTRY(entry_SYSENTER_compat) jnz sysenter_fix_flags sysenter_flags_fixed: + /* + * 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 + orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS) testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS) jnz sysenter_tracesys -- 2.20.1