diff options
author | Tony Luck <tony.luck@intel.com> | 2017-08-16 10:18:03 -0700 |
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committer | Ingo Molnar <mingo@kernel.org> | 2017-08-17 10:30:49 +0200 |
commit | ce0fa3e56ad20f04d8252353dcd24e924abdafca (patch) | |
tree | dee3cdb69e839f4eb1dc5690deb7e145202124c7 | |
parent | 57bd1905b228f2a14d7506b0302f69f425131e57 (diff) | |
download | linux-ce0fa3e56ad20f04d8252353dcd24e924abdafca.tar.bz2 |
x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages
Speculative processor accesses may reference any memory that has a
valid page table entry. While a speculative access won't generate
a machine check, it will log the error in a machine check bank. That
could cause escalation of a subsequent error since the overflow bit
will be then set in the machine check bank status register.
Code has to be double-plus-tricky to avoid mentioning the 1:1 virtual
address of the page we want to map out otherwise we may trigger the
very problem we are trying to avoid. We use a non-canonical address
that passes through the usual Linux table walking code to get to the
same "pte".
Thanks to Dave Hansen for reviewing several iterations of this.
Also see:
http://marc.info/?l=linux-mm&m=149860136413338&w=2
Signed-off-by: Tony Luck <tony.luck@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Elliott, Robert (Persistent Memory) <elliott@hpe.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20170816171803.28342-1-tony.luck@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r-- | arch/x86/include/asm/page_64.h | 4 | ||||
-rw-r--r-- | arch/x86/kernel/cpu/mcheck/mce.c | 43 | ||||
-rw-r--r-- | include/linux/mm_inline.h | 6 | ||||
-rw-r--r-- | mm/memory-failure.c | 2 |
4 files changed, 55 insertions, 0 deletions
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h index b4a0d43248cf..b50df06ad251 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -51,6 +51,10 @@ static inline void clear_page(void *page) void copy_page(void *to, void *from); +#ifdef CONFIG_X86_MCE +#define arch_unmap_kpfn arch_unmap_kpfn +#endif + #endif /* !__ASSEMBLY__ */ #ifdef CONFIG_X86_VSYSCALL_EMULATION diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 6dde0497efc7..3b413065c613 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -51,6 +51,7 @@ #include <asm/mce.h> #include <asm/msr.h> #include <asm/reboot.h> +#include <asm/set_memory.h> #include "mce-internal.h" @@ -1051,6 +1052,48 @@ static int do_memory_failure(struct mce *m) return ret; } +#if defined(arch_unmap_kpfn) && defined(CONFIG_MEMORY_FAILURE) + +void arch_unmap_kpfn(unsigned long pfn) +{ + unsigned long decoy_addr; + + /* + * Unmap this page from the kernel 1:1 mappings to make sure + * we don't log more errors because of speculative access to + * the page. + * We would like to just call: + * set_memory_np((unsigned long)pfn_to_kaddr(pfn), 1); + * but doing that would radically increase the odds of a + * speculative access to the posion page because we'd have + * the virtual address of the kernel 1:1 mapping sitting + * around in registers. + * Instead we get tricky. We create a non-canonical address + * that looks just like the one we want, but has bit 63 flipped. + * This relies on set_memory_np() not checking whether we passed + * a legal address. + */ + +/* + * Build time check to see if we have a spare virtual bit. Don't want + * to leave this until run time because most developers don't have a + * system that can exercise this code path. This will only become a + * problem if/when we move beyond 5-level page tables. + * + * Hard code "9" here because cpp doesn't grok ilog2(PTRS_PER_PGD) + */ +#if PGDIR_SHIFT + 9 < 63 + decoy_addr = (pfn << PAGE_SHIFT) + (PAGE_OFFSET ^ BIT(63)); +#else +#error "no unused virtual bit available" +#endif + + if (set_memory_np(decoy_addr, 1)) + pr_warn("Could not invalidate pfn=0x%lx from 1:1 map\n", pfn); + +} +#endif + /* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h index e030a68ead7e..25438b2b6f22 100644 --- a/include/linux/mm_inline.h +++ b/include/linux/mm_inline.h @@ -126,4 +126,10 @@ static __always_inline enum lru_list page_lru(struct page *page) #define lru_to_page(head) (list_entry((head)->prev, struct page, lru)) +#ifdef arch_unmap_kpfn +extern void arch_unmap_kpfn(unsigned long pfn); +#else +static __always_inline void arch_unmap_kpfn(unsigned long pfn) { } +#endif + #endif diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 1cd3b3569af8..88366626c0b7 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1146,6 +1146,8 @@ int memory_failure(unsigned long pfn, int trapno, int flags) return 0; } + arch_unmap_kpfn(pfn); + orig_head = hpage = compound_head(p); num_poisoned_pages_inc(); |