src/patches/libsafe-functioncaching.diff

   1 From: Goswin Brederlow <goswin.brederlow@student.uni-tuebingen.de>
   2 Subject: Bug#129345: patch to prevent a loop between libdl and libsafe causing libdl to crash
   3 To: 129345@bugs.debian.org
   4 Date: 01 Sep 2002 23:54:35 +0200
   5 Reply-To: Goswin Brederlow <goswin.brederlow@student.uni-tuebingen.de>,
   6         129345@bugs.debian.org
   7 Resent-From: Goswin Brederlow <goswin.brederlow@student.uni-tuebingen.de>
   8
   9
  10 -------
  11 [D. Coe edited this patch slightly -- moved an unrelated change into the
  12 Makefile itself [it changed the debugging comments only], and corrected a
  13 spelling error and reworded the comments.  The original patch is in the
  14 bug tracking system, if you want to see it as submitted by Goswin.]
  15 -------
  16 -------
  17 D. Coe subsequently modified the patch further, because in some cases
  18 the initializations did not occur (e.g. when IO_vfscanf or memcpy was
  19 called from ps or top (likely one of the libraries they use).  maybe
  20 they do something that disables libsafe's library globals initialization?
  21
  22
  23 In any case, I've adopted both strategise in this new patch; the addresses
  24 are preloaded as Goswin had coded, but they are also individually checked
  25 each time needed (as was the case before Goswin's patch), and are initialized
  26 at that point if necessary.  Hopefully this will let ps and top work
  27 and also continue to work around the libdl problem.
  28 -------
  29
  30 Hi,
  31
  32 if libsafe is invoked from inside libdl (or only inside dlerror()?)
  33 and a real_XXX function is not yet looked up it will reenter
  34 libdl. That causes memory corruption resulting in a read from 0x0 and
  35 thus segfault.
  36
  37 The patch below makes libsafe cache all needed symbols once upon
  38 init. That not only causes less lookups than before but should prevent
  39 fatal loops. Failures of the initial lookups might not be reported
  40 correctly but terminate in some odd way if the functions needed to
  41 report are not yet looked up.
  42
  43 MfG
  44         Goswin
  45
  46 ----------------------------------------------------------------------
  47 diff -Nurd libsafe-2.0-16/src/intercept.c libsafe-2.0-16-mrvn/src/intercept.c
  48 --- libsafe-2.0-16/src/intercept.c      2002-05-31 19:37:34.000000000 +0200
  49 +++ libsafe-2.0-16-mrvn/src/intercept.c 2002-09-01 23:44:55.000000000 +0200
  50 @@ -128,14 +128,29 @@
  51  }
  52
  53
  54 -/* Starting with version 2.0, we keep a single global copy of the pointer to
  55 - * the real memcpy() function.  This allows us to call
  56 - * getLibraryFunction("memcpy") just once instead of multiple times, since
  57 - * memcpy() is needed in four different functions below.
  58 +/* Starting with Debian version 2.0-16-2, we keep a global copy of the pointer
  59 + * to each real functions.  Otherwise a getLibraryFunction might
  60 + * be triggered from inside dlsym() and cause memory corruption reulting in a
  61 + * segfault.
  62   */
  63 -static memcpy_t real_memcpy = NULL;
  64 -
  65 -
  66 +static memcpy_t      real_memcpy = NULL;
  67 +static _IO_vfscanf_t real_IO_vfscanf = NULL;
  68 +static vfprintf_t    real_vfprintf = NULL;
  69 +static vsnprintf_t   real_vsnprintf = NULL;
  70 +static vsprintf_t    real_vsprintf = NULL;
  71 +static gets_t        real_gets = NULL;
  72 +static getwd_t       real_getwd = NULL;
  73 +static realpath_t    real_realpath = NULL;
  74 +static stpcpy_t      real_stpcpy = NULL;
  75 +static strcat_t      real_strcat = NULL;
  76 +static strcpy_t      real_strcpy = NULL;
  77 +static strncat_t     real_strncat = NULL;
  78 +static strncpy_t     real_strncpy = NULL;
  79 +static wcscpy_t      real_wcscpy = NULL;
  80 +static wcpcpy_t      real_wcpcpy = NULL;
  81 +#ifndef MISSING_WCSNLEN
  82 +static wcscat_t      real_wcscat = NULL;
  83 +#endif
  84  /*
  85   * -------------- system library implementations -------------------
  86   * Here is the story: if a C source file includes <string.h> and is
  87 @@ -150,7 +165,6 @@
  88   */
  89  char *strcpy(char *dest, const char *src)
  90  {
  91 -    static strcpy_t real_strcpy = NULL;
  92      size_t max_size, len;
  93
  94      if (!real_memcpy)
  95 @@ -182,7 +196,6 @@
  96
  97  char *strncpy(char *dest, const char *src, size_t n)
  98  {
  99 -    static strncpy_t real_strncpy = NULL;
 100      size_t max_size, len;
 101
 102      if (!real_strncpy)
 103 @@ -206,7 +219,6 @@
 104
 105  char *stpcpy(char *dest, const char *src)
 106  {
 107 -    static stpcpy_t real_stpcpy = NULL;
 108      size_t max_size, len;
 109
 110      if (!real_memcpy)
 111 @@ -239,7 +251,6 @@
 112  #ifndef MISSING_WCSNLEN
 113  wchar_t *wcscpy(wchar_t *dest, const wchar_t *src)
 114  {
 115 -    static wcscpy_t real_wcscpy = NULL;
 116      size_t max_bytes, max_wchars, len;
 117
 118      if (!real_wcscpy)
 119 @@ -280,7 +291,6 @@
 120
 121  wchar_t *wcpcpy(wchar_t *dest, const wchar_t *src)
 122  {
 123 -    static wcpcpy_t real_wcpcpy = NULL;
 124      size_t max_bytes, max_wchars, len;
 125
 126      if (!real_wcpcpy)
 127 @@ -347,7 +357,6 @@
 128
 129  char *strcat(char *dest, const char *src)
 130  {
 131 -    static strcat_t real_strcat = NULL;
 132      size_t max_size;
 133      uint dest_len, src_len;
 134
 135 @@ -379,7 +388,6 @@
 136
 137  char *strncat(char *dest, const char *src, size_t n)
 138  {
 139 -    static strncat_t real_strncat = NULL;
 140      size_t max_size;
 141      uint dest_len, src_len;
 142
 143 @@ -408,7 +416,6 @@
 144  #ifndef MISSING_WCSNLEN
 145  wchar_t *wcscat(wchar_t *dest, const wchar_t *src)
 146  {
 147 -    static wcscat_t real_wcscat = NULL;
 148      size_t max_bytes;
 149      uint dest_len, src_len;
 150
 151 @@ -861,7 +868,6 @@
 152   */
 153  int vfprintf(FILE *fp, const char *format, va_list ap)
 154  {
 155 -    static vfprintf_t real_vfprintf = NULL;
 156      int res;
 157      char *p, *pnum;
 158      int c = -1;                /* Next var arg to be used */
 159 @@ -1026,7 +1032,6 @@
 160   */
 161  int _IO_vfprintf(FILE *fp, const char *format, va_list ap)
 162  {
 163 -    static vfprintf_t real_vfprintf = NULL;
 164      int res;
 165      char *p, *pnum;
 166      int c = -1;                /* Next var arg to be used */
 167 @@ -1189,8 +1194,6 @@
 168
 169  int sprintf(char *str, const char *format, ...)
 170  {
 171 -    static vsprintf_t real_vsprintf = NULL;
 172 -    static vsnprintf_t real_vsnprintf = NULL;
 173      size_t max_size;
 174      va_list ap;
 175      int res;
 176 @@ -1239,7 +1242,6 @@
 177
 178  int snprintf(char *str, size_t size, const char *format, ...)
 179  {
 180 -    static vsnprintf_t real_vsnprintf = NULL;
 181      size_t max_size;
 182      va_list ap;
 183      int res;
 184 @@ -1286,8 +1288,6 @@
 185
 186  int vsprintf(char *str, const char *format, va_list ap)
 187  {
 188 -    static vsprintf_t real_vsprintf = NULL;
 189 -    static vsnprintf_t real_vsnprintf = NULL;
 190      size_t max_size;
 191      int res;
 192
 193 @@ -1325,7 +1325,6 @@
 194
 195  int vsnprintf(char *str, size_t size, const char *format, va_list ap)
 196  {
 197 -    static vsnprintf_t real_vsnprintf = NULL;
 198      size_t max_size;
 199      int res;
 200
 201 @@ -1361,7 +1360,6 @@
 202
 203  char *getwd(char *buf)
 204  {
 205 -    static getwd_t real_getwd = NULL;
 206      size_t max_size;
 207      char *res;
 208
 209 @@ -1386,7 +1384,6 @@
 210
 211  char *gets(char *s)
 212  {
 213 -    static gets_t real_gets = NULL;
 214      size_t max_size, len;
 215
 216      if (!real_gets)
 217 @@ -1412,7 +1409,6 @@
 218
 219  char *realpath(char *path, char resolved_path[])
 220  {
 221 -    static realpath_t real_realpath = NULL;
 222      size_t max_size, len;
 223      char *res;
 224      char buf[MAXPATHLEN + 1];
 225 @@ -1445,7 +1441,6 @@
 226
 227  int _IO_vfscanf (_IO_FILE *s, const char *format, _IO_va_list argptr, int *errp)
 228  {
 229 -    static _IO_vfscanf_t real_IO_vfscanf = NULL;
 230      int res, save_count;
 231      caddr_t ra_array[MAXLEVELS], fp_array[MAXLEVELS];
 232
 233 @@ -1529,6 +1524,25 @@
 234
 235         fclose(fp);
 236      }
 237 +
 238 +    real_memcpy = (memcpy_t) getLibraryFunction("memcpy");
 239 +    real_IO_vfscanf = (_IO_vfscanf_t) getLibraryFunction("_IO_vfscanf");
 240 +    real_vfprintf = (vfprintf_t) getLibraryFunction("vfprintf");
 241 +    real_vsnprintf = (vsnprintf_t) getLibraryFunction("vsnprintf");
 242 +    real_vsprintf = (vsprintf_t) getLibraryFunction("vsprintf");
 243 +    real_gets = (gets_t) getLibraryFunction("gets");
 244 +    real_getwd = (getwd_t) getLibraryFunction("getwd");
 245 +    real_realpath = (realpath_t) getLibraryFunction("realpath");
 246 +    real_stpcpy = (stpcpy_t) getLibraryFunction("stpcpy");
 247 +    real_strcat = (strcat_t) getLibraryFunction("strcat");
 248 +    real_strcpy = (strcpy_t) getLibraryFunction("strcpy");
 249 +    real_strncat = (strncat_t) getLibraryFunction("strncat");
 250 +    real_strncpy = (strncpy_t) getLibraryFunction("strncpy");
 251 +    real_wcscpy = (wcscpy_t) getLibraryFunction("wcscpy");
 252 +    real_wcpcpy = (wcpcpy_t) getLibraryFunction("wcpcpy");
 253 +#ifndef MISSING_WCSNLEN
 254 +    real_wcscat = (wcscat_t) getLibraryFunction("wcscat");
 255 +#endif
 256  }
 257
 258