Commit-ID:  603e492e861861ddfec7139a007abad74f0d3af0
Gitweb:     http://git.kernel.org/tip/603e492e861861ddfec7139a007abad74f0d3af0
Author:     Andy Lutomirski <l...@kernel.org>
AuthorDate: Wed, 9 Aug 2017 14:39:45 -0700
Committer:  Ingo Molnar <mi...@kernel.org>
CommitDate: Thu, 10 Aug 2017 13:14:58 +0200

x86/asm/32: Fix regs_get_register() on segment registers

The segment register high words on x86_32 may contain garbage.
Teach regs_get_register() to read them as u16 instead of unsigned
long.

Signed-off-by: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Link: 
http://lkml.kernel.org/r/0b76f6dbe477b7b1a81938fddcc3c483d48f0ff2.1502314765.git.l...@kernel.org
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 arch/x86/include/asm/ptrace.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index a29f828..91c04c8 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -196,6 +196,17 @@ static inline unsigned long regs_get_register(struct 
pt_regs *regs,
        if (offset == offsetof(struct pt_regs, sp) &&
            regs->cs == __KERNEL_CS)
                return kernel_stack_pointer(regs);
+
+       /* The selector fields are 16-bit. */
+       if (offset == offsetof(struct pt_regs, cs) ||
+           offset == offsetof(struct pt_regs, ss) ||
+           offset == offsetof(struct pt_regs, ds) ||
+           offset == offsetof(struct pt_regs, es) ||
+           offset == offsetof(struct pt_regs, fs) ||
+           offset == offsetof(struct pt_regs, gs)) {
+               return *(u16 *)((unsigned long)regs + offset);
+
+       }
 #endif
        return *(unsigned long *)((unsigned long)regs + offset);
 }

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