From 0caec70692a0f19538ed4ebb816df0d5585c8bd0 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 1 Aug 2017 07:11:35 -0700 Subject: [PATCH] x86/fsgsbase/64: Report FSBASE and GSBASE correctly in core dumps commit 9584d98bed7a7a904d0702ad06bbcc94703cb5b4 upstream. In ELF_COPY_CORE_REGS, we're copying from the current task, so accessing thread.fsbase and thread.gsbase makes no sense. Just read the values from the CPU registers. In practice, the old code would have been correct most of the time simply because thread.fsbase and thread.gsbase usually matched the CPU registers. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Chang Seok Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/elf.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h index b31761e..7bcd138 100644 --- a/arch/x86/include/asm/elf.h +++ b/arch/x86/include/asm/elf.h @@ -204,6 +204,7 @@ void set_personality_ia32(bool); #define ELF_CORE_COPY_REGS(pr_reg, regs) \ do { \ + unsigned long base; \ unsigned v; \ (pr_reg)[0] = (regs)->r15; \ (pr_reg)[1] = (regs)->r14; \ @@ -226,8 +227,8 @@ do { \ (pr_reg)[18] = (regs)->flags; \ (pr_reg)[19] = (regs)->sp; \ (pr_reg)[20] = (regs)->ss; \ - (pr_reg)[21] = current->thread.fsbase; \ - (pr_reg)[22] = current->thread.gsbase; \ + rdmsrl(MSR_FS_BASE, base); (pr_reg)[21] = base; \ + rdmsrl(MSR_KERNEL_GS_BASE, base); (pr_reg)[22] = base; \ asm("movl %%ds,%0" : "=r" (v)); (pr_reg)[23] = v; \ asm("movl %%es,%0" : "=r" (v)); (pr_reg)[24] = v; \ asm("movl %%fs,%0" : "=r" (v)); (pr_reg)[25] = v; \ -- 2.7.4