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 <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chang Seok <chang.seok.bae@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index bcd3d6199464701f1e50a39ebfcf856c9d5c013f..bb16a58cf7e4d96697a5f9f525a806a1af94ddf1 100644 (file)
--- 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.fs;                      \
-       (pr_reg)[22] = current->thread.gs;                      \
+       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;       \