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| author | Alexander Potapenko <glider@google.com> | 2017-08-16 21:08:08 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-08-17 09:53:00 +0200 |
| commit | 187e91fe5e915f4b7f39b824aa422493463e443d (patch) | |
| tree | 4b2c8fe90f4d4be61b2a25ceb1c5a6fe20d6aad0 /arch | |
| parent | 01578e36163cdd0e4fd61d9976de15f13364e26d (diff) | |
| download | linux-0-day-187e91fe5e915f4b7f39b824aa422493463e443d.tar.gz linux-0-day-187e91fe5e915f4b7f39b824aa422493463e443d.tar.xz | |
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/head64.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 46c3c73e7f43f..9ba79543d9ee9 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -53,6 +53,7 @@ void __head __startup_64(unsigned long physaddr) pudval_t *pud; pmdval_t *pmd, pmd_entry; int i; + unsigned int *next_pgt_ptr; /* Is the address too large? */ if (physaddr >> MAX_PHYSMEM_BITS) @@ -91,9 +92,9 @@ void __head __startup_64(unsigned long physaddr) * creates a bunch of nonsense entries but that is fine -- * it avoids problems around wraparound. */ - - pud = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr); - pmd = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr); + next_pgt_ptr = fixup_pointer(&next_early_pgt, physaddr); + pud = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr); + pmd = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr); if (IS_ENABLED(CONFIG_X86_5LEVEL)) { p4d = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr); |