src/patches/suse-2.6.27.25/patches.suse/x86-mark_rodata_rw.patch

   1 From: Nick Piggin <npiggin@novell.com>
   2 Subject: Add mark_rodata_rw() to un-protect read-only kernel code pages
   3 References: bnc#439348
   4
   5 CONFIG_RODATA presents a problem for antivirus vendors who do not have a
   6 clean user-space interface for getting virus scanning triggered, and
   7 currently resort to patching the kernel code instead (presumably the
   8 ystem call table). With CONFIG_RODATA enabled, the kernel rejects such
   9 write accesses.
  10
  11 Add a new mark_rodata_rw() function to un-protect the read-only kernel code
  12 pages for now, and export mark_rodata_ro() and mark_rodata_rw() to modules.
  13
  14 This is not meant as a permanent workaround, and will be removed again in the
  15 next release!
  16
  17 Acked-by: Andres Gruenbacher <agruen@suse.de>
  18
  19 ---
  20  arch/x86/mm/init_32.c        |   22 ++++++++++++++++++++++
  21  arch/x86/mm/init_64.c        |   17 +++++++++++++++++
  22  arch/x86/mm/pageattr.c       |   30 ++++++++++++++++++++++++++++--
  23  include/asm-x86/cacheflush.h |    3 +++
  24  4 files changed, 70 insertions(+), 2 deletions(-)
  25
  26 --- a/arch/x86/mm/init_32.c
  27 +++ b/arch/x86/mm/init_32.c
  28 @@ -1073,6 +1073,28 @@ void mark_rodata_ro(void)
  29         set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);
  30  #endif
  31  }
  32 +EXPORT_SYMBOL(mark_rodata_ro);
  33 +
  34 +void mark_rodata_rw(void)
  35 +{
  36 +       unsigned long start = PFN_ALIGN(_text);
  37 +       unsigned long size = PFN_ALIGN(_etext) - start;
  38 +
  39 +#ifndef CONFIG_DYNAMIC_FTRACE
  40 +       /* Dynamic tracing modifies the kernel text section */
  41 +       set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
  42 +       printk(KERN_INFO "Write enabling the kernel text: %luk\n",
  43 +               size >> 10);
  44 +
  45 +#endif /* CONFIG_DYNAMIC_FTRACE */
  46 +
  47 +       start += size;
  48 +       size = (unsigned long)__end_rodata - start;
  49 +       set_pages_rw_force(virt_to_page(start), size >> PAGE_SHIFT);
  50 +       printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
  51 +               size >> 10);
  52 +}
  53 +EXPORT_SYMBOL(mark_rodata_rw);
  54  #endif
  55
  56  void free_init_pages(char *what, unsigned long begin, unsigned long end)
  57 --- a/arch/x86/mm/init_64.c
  58 +++ b/arch/x86/mm/init_64.c
  59 @@ -896,7 +896,24 @@ void mark_rodata_ro(void)
  60         set_memory_ro(start, (end-start) >> PAGE_SHIFT);
  61  #endif
  62  }
  63 +EXPORT_SYMBOL(mark_rodata_ro);
  64
  65 +void mark_rodata_rw(void)
  66 +{
  67 +       unsigned long start = PFN_ALIGN(_stext), end = PFN_ALIGN(__end_rodata);
  68 +       unsigned long rodata_start =
  69 +               ((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;
  70 +
  71 +#ifdef CONFIG_DYNAMIC_FTRACE
  72 +       /* Dynamic tracing modifies the kernel text section */
  73 +       start = rodata_start;
  74 +#endif
  75 +
  76 +       printk(KERN_INFO "Write enabling the kernel read-only data: %luk\n",
  77 +              (end - start) >> 10);
  78 +       set_memory_rw_force(start, (end - start) >> PAGE_SHIFT);
  79 +}
  80 +EXPORT_SYMBOL(mark_rodata_rw);
  81  #endif
  82
  83  #ifdef CONFIG_BLK_DEV_INITRD
  84 --- a/arch/x86/mm/pageattr.c
  85 +++ b/arch/x86/mm/pageattr.c
  86 @@ -190,6 +190,8 @@ static void cpa_flush_range(unsigned lon
  87         }
  88  }
  89
  90 +static int static_protections_allow_rodata __read_mostly;
  91 +
  92  /*
  93   * Certain areas of memory on x86 require very specific protection flags,
  94   * for example the BIOS area or kernel text. Callers don't always get this
  95 @@ -221,8 +223,10 @@ static inline pgprot_t static_protection
  96          * catches all aliases.
  97          */
  98         if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
  99 -                  __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
 100 -               pgprot_val(forbidden) |= _PAGE_RW;
 101 +                  __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) {
 102 +               if (!static_protections_allow_rodata)
 103 +                       pgprot_val(forbidden) |= _PAGE_RW;
 104 +       }
 105
 106         prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));
 107
 108 @@ -956,6 +960,21 @@ int set_memory_rw(unsigned long addr, in
 109         return change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
 110  }
 111
 112 +/* hack: bypass kernel rodata section static_protections check. */
 113 +int set_memory_rw_force(unsigned long addr, int numpages)
 114 +{
 115 +       static DEFINE_MUTEX(lock);
 116 +       int ret;
 117 +
 118 +       mutex_lock(&lock);
 119 +       static_protections_allow_rodata = 1;
 120 +       ret = change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
 121 +       static_protections_allow_rodata = 0;
 122 +       mutex_unlock(&lock);
 123 +
 124 +       return ret;
 125 +}
 126 +
 127  int set_memory_np(unsigned long addr, int numpages)
 128  {
 129         return change_page_attr_clear(addr, numpages, __pgprot(_PAGE_PRESENT));
 130 @@ -1013,6 +1032,13 @@ int set_pages_rw(struct page *page, int
 131         return set_memory_rw(addr, numpages);
 132  }
 133
 134 +int set_pages_rw_force(struct page *page, int numpages)
 135 +{
 136 +       unsigned long addr = (unsigned long)page_address(page);
 137 +
 138 +       return set_memory_rw_force(addr, numpages);
 139 +}
 140 +
 141  #ifdef CONFIG_DEBUG_PAGEALLOC
 142
 143  static int __set_pages_p(struct page *page, int numpages)
 144 --- a/include/asm-x86/cacheflush.h
 145 +++ b/include/asm-x86/cacheflush.h
 146 @@ -63,6 +63,7 @@ int set_memory_x(unsigned long addr, int
 147  int set_memory_nx(unsigned long addr, int numpages);
 148  int set_memory_ro(unsigned long addr, int numpages);
 149  int set_memory_rw(unsigned long addr, int numpages);
 150 +int set_memory_rw_force(unsigned long addr, int numpages);
 151  int set_memory_np(unsigned long addr, int numpages);
 152  int set_memory_4k(unsigned long addr, int numpages);
 153
 154 @@ -92,6 +93,7 @@ int set_pages_x(struct page *page, int n
 155  int set_pages_nx(struct page *page, int numpages);
 156  int set_pages_ro(struct page *page, int numpages);
 157  int set_pages_rw(struct page *page, int numpages);
 158 +int set_pages_rw_force(struct page *page, int numpages);
 159
 160
 161  void clflush_cache_range(void *addr, unsigned int size);
 162 @@ -100,6 +102,7 @@ void cpa_init(void);
 163
 164  #ifdef CONFIG_DEBUG_RODATA
 165  void mark_rodata_ro(void);
 166 +void mark_rodata_rw(void);
 167  extern const int rodata_test_data;
 168  #endif
 169