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authorAlexander Potapenko <glider@google.com>2017-08-16 22:08:08 +0300
committerIngo Molnar <mingo@kernel.org>2017-08-17 10:53:00 +0300
commit187e91fe5e915f4b7f39b824aa422493463e443d (patch)
tree4b2c8fe90f4d4be61b2a25ceb1c5a6fe20d6aad0 /arch
parent01578e36163cdd0e4fd61d9976de15f13364e26d (diff)
downloadlinux-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.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 46c3c73e7f43..9ba79543d9ee 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);