From: Borislav Petkov Date: Sun, 27 Aug 2017 16:39:24 +0000 (+0200) Subject: x86/mm: Fix SME encryption stack ptr handling X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=6e0b52d406f64d2bd65731968a072387b91b44d2;p=openwrt%2Fstaging%2Fblogic.git x86/mm: Fix SME encryption stack ptr handling sme_encrypt_execute() stashes the stack pointer on entry into %rbp because it allocates a one-page stack in the non-encrypted area for the encryption routine to use. When the latter is done, it restores it from %rbp again, before returning. However, it uses the FRAME_* macros partially but restores %rsp from %rbp explicitly with a MOV. And this is fine as long as the macros *actually* do something. Unless, you do a !CONFIG_FRAME_POINTER build where those macros are empty. Then, we still restore %rsp from %rbp but %rbp contains *something* and this leads to a stack corruption. The manifestation being a triple-fault during early boot when testing SME. Good luck to me debugging this with the clumsy endless-loop-in-asm method and narrowing it down gradually. :-( So, long story short, open-code the frame macros so that there's no monkey business and we avoid subtly breaking SME depending on the .config. Fixes: 6ebcb060713f ("x86/mm: Add support to encrypt the kernel in-place") Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Acked-by: Tom Lendacky Cc: Brijesh Singh Link: http://lkml.kernel.org/r/20170827163924.25552-1-bp@alien8.de --- diff --git a/arch/x86/mm/mem_encrypt_boot.S b/arch/x86/mm/mem_encrypt_boot.S index b327e0472448..730e6d541df1 100644 --- a/arch/x86/mm/mem_encrypt_boot.S +++ b/arch/x86/mm/mem_encrypt_boot.S @@ -15,7 +15,6 @@ #include #include #include -#include .text .code64 @@ -33,7 +32,8 @@ ENTRY(sme_encrypt_execute) * R8 - physcial address of the pagetables to use for encryption */ - FRAME_BEGIN /* RBP now has original stack pointer */ + push %rbp + movq %rsp, %rbp /* RBP now has original stack pointer */ /* Set up a one page stack in the non-encrypted memory area */ movq %rcx, %rax /* Workarea stack page */ @@ -64,7 +64,7 @@ ENTRY(sme_encrypt_execute) pop %r12 movq %rbp, %rsp /* Restore original stack pointer */ - FRAME_END + pop %rbp ret ENDPROC(sme_encrypt_execute)