1. 25 2月, 2016 1 次提交
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    • T
      x86/mm: Fix vmalloc_fault() to handle large pages properly · f4eafd8b
      Toshi Kani 提交于
      A kernel page fault oops with the callstack below was observed
      when a read syscall was made to a pmem device after a huge amount
      (>512GB) of vmalloc ranges was allocated by ioremap() on a x86_64
      system:
      
           BUG: unable to handle kernel paging request at ffff880840000ff8
           IP: vmalloc_fault+0x1be/0x300
           PGD c7f03a067 PUD 0
           Oops: 0000 [#1] SM
           Call Trace:
              __do_page_fault+0x285/0x3e0
              do_page_fault+0x2f/0x80
              ? put_prev_entity+0x35/0x7a0
              page_fault+0x28/0x30
              ? memcpy_erms+0x6/0x10
              ? schedule+0x35/0x80
              ? pmem_rw_bytes+0x6a/0x190 [nd_pmem]
              ? schedule_timeout+0x183/0x240
              btt_log_read+0x63/0x140 [nd_btt]
               :
              ? __symbol_put+0x60/0x60
              ? kernel_read+0x50/0x80
              SyS_finit_module+0xb9/0xf0
              entry_SYSCALL_64_fastpath+0x1a/0xa4
      
      Since v4.1, ioremap() supports large page (pud/pmd) mappings in
      x86_64 and PAE.  vmalloc_fault() however assumes that the vmalloc
      range is limited to pte mappings.
      
      vmalloc faults do not normally happen in ioremap'd ranges since
      ioremap() sets up the kernel page tables, which are shared by
      user processes.  pgd_ctor() sets the kernel's PGD entries to
      user's during fork().  When allocation of the vmalloc ranges
      crosses a 512GB boundary, ioremap() allocates a new pud table
      and updates the kernel PGD entry to point it.  If user process's
      PGD entry does not have this update yet, a read/write syscall
      to the range will cause a vmalloc fault, which hits the Oops
      above as it does not handle a large page properly.
      
      Following changes are made to vmalloc_fault().
      
      64-bit:
      
       - No change for the PGD sync operation as it handles large
         pages already.
       - Add pud_huge() and pmd_huge() to the validation code to
         handle large pages.
       - Change pud_page_vaddr() to pud_pfn() since an ioremap range
         is not directly mapped (while the if-statement still works
         with a bogus addr).
       - Change pmd_page() to pmd_pfn() since an ioremap range is not
         backed by struct page (while the if-statement still works
         with a bogus addr).
      
      32-bit:
       - No change for the sync operation since the index3 PGD entry
         covers the entire vmalloc range, which is always valid.
         (A separate change to sync PGD entry is necessary if this
          memory layout is changed regardless of the page size.)
       - Add pmd_huge() to the validation code to handle large pages.
         This is for completeness since vmalloc_fault() won't happen
         in ioremap'd ranges as its PGD entry is always valid.
      Reported-by: NHenning Schild <henning.schild@siemens.com>
      Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
      Acked-by: NBorislav Petkov <bp@alien8.de>
      Cc: <stable@vger.kernel.org> # 4.1+
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Luis R. Rodriguez <mcgrof@suse.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Toshi Kani <toshi.kani@hp.com>
      Cc: linux-mm@kvack.org
      Cc: linux-nvdimm@lists.01.org
      Link: http://lkml.kernel.org/r/1455758214-24623-1-git-send-email-toshi.kani@hpe.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      f4eafd8b
  6. 17 2月, 2016 7 次提交
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