x86/boot/64/clang: Use fixup_pointer() to access 'next_early_pgt'
authorAlexander Potapenko <glider@google.com>
Wed, 16 Aug 2017 19:08:08 +0000 (21:08 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 17 Aug 2017 07:53:00 +0000 (09:53 +0200)
commit187e91fe5e915f4b7f39b824aa422493463e443d
tree4b2c8fe90f4d4be61b2a25ceb1c5a6fe20d6aad0
parent01578e36163cdd0e4fd61d9976de15f13364e26d
x86/boot/64/clang: Use fixup_pointer() to access 'next_early_pgt'

__startup_64() is normally using fixup_pointer() to access globals in a
position-independent fashion. However 'next_early_pgt' was accessed
directly, which wasn't guaranteed to work.

Luckily GCC was generating a R_X86_64_PC32 PC-relative relocation for
'next_early_pgt', but Clang emitted a R_X86_64_32S, which led to
accessing invalid memory and rebooting the kernel.

Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Davidson <md@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: c88d71508e36 ("x86/boot/64: Rewrite startup_64() in C")
Link: http://lkml.kernel.org/r/20170816190808.131748-1-glider@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/kernel/head64.c