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CVE-2015-1472: wscanf allocates too little memory
BZ #16618 Under certain conditions wscanf can allocate too little memory for the to-be-scanned arguments and overflow the allocated buffer. The implementation now correctly computes the required buffer size when using malloc. A regression test was added to tst-sscanf.
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@ -1,3 +1,11 @@
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2015-02-05 Paul Pluzhnikov <ppluzhnikov@google.com>
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[BZ #16618]
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* stdio-common/tst-sscanf.c (main): Test for buffer overflow.
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* stdio-common/vfscanf.c (_IO_vfscanf_internal): Compute needed
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size in bytes. Store needed elements in wpmax. Use needed size
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in bytes for extend_alloca.
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2015-02-05 Carlos O'Donell <carlos@systemhalted.org>
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* manual/install.texi: Latest tested versions are GCC 4.9.2,
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24
NEWS
24
NEWS
@ -10,15 +10,21 @@ Version 2.21
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* The following bugs are resolved with this release:
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6652, 10672, 12674, 12847, 12926, 13862, 14132, 14138, 14171, 14498,
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15215, 15378, 15884, 16009, 16418, 16191, 16469, 16576, 16617, 16619,
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16657, 16740, 16857, 17192, 17266, 17273, 17344, 17363, 17370, 17371,
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17411, 17460, 17475, 17485, 17501, 17506, 17508, 17522, 17555, 17570,
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17571, 17572, 17573, 17574, 17582, 17583, 17584, 17585, 17589, 17594,
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17601, 17608, 17616, 17625, 17630, 17633, 17634, 17635, 17647, 17653,
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17657, 17658, 17664, 17665, 17668, 17682, 17702, 17717, 17719, 17722,
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17723, 17724, 17725, 17732, 17733, 17744, 17745, 17746, 17747, 17748,
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17775, 17777, 17780, 17781, 17782, 17791, 17793, 17796, 17797, 17801,
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17803, 17806, 17834, 17844, 17848, 17868, 17869, 17870, 17885, 17892.
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15215, 15378, 15884, 16009, 16418, 16191, 16469, 16576, 16617, 16618,
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16619, 16657, 16740, 16857, 17192, 17266, 17273, 17344, 17363, 17370,
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17371, 17411, 17460, 17475, 17485, 17501, 17506, 17508, 17522, 17555,
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17570, 17571, 17572, 17573, 17574, 17582, 17583, 17584, 17585, 17589,
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17594, 17601, 17608, 17616, 17625, 17630, 17633, 17634, 17635, 17647,
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17653, 17657, 17658, 17664, 17665, 17668, 17682, 17702, 17717, 17719,
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17722, 17723, 17724, 17725, 17732, 17733, 17744, 17745, 17746, 17747,
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17748, 17775, 17777, 17780, 17781, 17782, 17791, 17793, 17796, 17797,
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17801, 17803, 17806, 17834, 17844, 17848, 17868, 17869, 17870, 17885,
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17892.
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* CVE-2015-1472 Under certain conditions wscanf can allocate too little
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memory for the to-be-scanned arguments and overflow the allocated
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buffer. The implementation now correctly computes the required buffer
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size when using malloc.
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* A new semaphore algorithm has been implemented in generic C code for all
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machines. Previous custom assembly implementations of semaphore were
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@ -233,5 +233,38 @@ main (void)
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}
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}
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/* BZ #16618
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The test will segfault during SSCANF if the buffer overflow
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is not fixed. The size of `s` is such that it forces the use
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of malloc internally and this triggers the incorrect computation.
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Thus the value for SIZE is arbitrariy high enough that malloc
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is used. */
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{
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#define SIZE 131072
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CHAR *s = malloc ((SIZE + 1) * sizeof (*s));
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if (s == NULL)
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abort ();
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for (size_t i = 0; i < SIZE; i++)
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s[i] = L('0');
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s[SIZE] = L('\0');
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int i = 42;
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/* Scan multi-digit zero into `i`. */
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if (SSCANF (s, L("%d"), &i) != 1)
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{
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printf ("FAIL: bug16618: SSCANF did not read one input item.\n");
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result = 1;
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}
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if (i != 0)
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{
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printf ("FAIL: bug16618: Value of `i` was not zero as expected.\n");
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result = 1;
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}
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free (s);
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if (result != 1)
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printf ("PASS: bug16618: Did not crash.\n");
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#undef SIZE
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}
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return result;
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}
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@ -272,9 +272,10 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
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if (__glibc_unlikely (wpsize == wpmax)) \
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{ \
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CHAR_T *old = wp; \
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size_t newsize = (UCHAR_MAX + 1 > 2 * wpmax \
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? UCHAR_MAX + 1 : 2 * wpmax); \
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if (use_malloc || !__libc_use_alloca (newsize)) \
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bool fits = __glibc_likely (wpmax <= SIZE_MAX / sizeof (CHAR_T) / 2); \
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size_t wpneed = MAX (UCHAR_MAX + 1, 2 * wpmax); \
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size_t newsize = fits ? wpneed * sizeof (CHAR_T) : SIZE_MAX; \
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if (!__libc_use_alloca (newsize)) \
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{ \
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wp = realloc (use_malloc ? wp : NULL, newsize); \
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if (wp == NULL) \
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@ -286,14 +287,13 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
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} \
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if (! use_malloc) \
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MEMCPY (wp, old, wpsize); \
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wpmax = newsize; \
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wpmax = wpneed; \
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use_malloc = true; \
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} \
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else \
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{ \
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size_t s = wpmax * sizeof (CHAR_T); \
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wp = (CHAR_T *) extend_alloca (wp, s, \
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newsize * sizeof (CHAR_T)); \
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wp = (CHAR_T *) extend_alloca (wp, s, newsize); \
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wpmax = s / sizeof (CHAR_T); \
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if (old != NULL) \
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MEMCPY (wp, old, wpsize); \
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