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Message-Id: <1a6c4d3a8a4e7be79ba448b42685e0321d50c14c.1461698311.git.luto@kernel.org> Date: Tue, 26 Apr 2016 12:23:27 -0700 From: Andy Lutomirski <luto@...nel.org> To: x86@...nel.org Cc: linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>, Brian Gerst <brgerst@...il.com>, Andi Kleen <andi@...stfloor.org>, Andy Lutomirski <luto@...nel.org> Subject: [PATCH 4/8] x86/segments/64: When load_gs_index fails, clear the base On AMD CPUs, a failed load_gs_base currently may not clear the FS base. Fix it. Signed-off-by: Andy Lutomirski <luto@...nel.org> --- arch/x86/entry/entry_64.S | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 1693c17dbf81..6344629ae1ce 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -794,6 +794,12 @@ END(native_load_gs_index) /* running with kernelgs */ bad_gs: SWAPGS /* switch back to user gs */ +.macro ZAP_GS + /* This can't be a string because the preprocessor needs to see it. */ + movl $__USER_DS, %eax + movl %eax, %gs +.endm + ALTERNATIVE "", "ZAP_GS", X86_BUG_NULL_SEG xorl %eax, %eax movl %eax, %gs jmp 2b -- 2.5.5
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