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89 lines
3.0 KiB
89 lines
3.0 KiB
commit 5bd80bfe9ca0d955bfbbc002781bc7b01b6bcb06 |
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Author: Paul Pluzhnikov <ppluzhnikov@google.com> |
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Date: Fri Feb 6 00:30:42 2015 -0500 |
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CVE-2015-1472: wscanf allocates too little memory |
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BZ #16618 |
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Under certain conditions wscanf can allocate too little memory for the |
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to-be-scanned arguments and overflow the allocated buffer. The |
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implementation now correctly computes the required buffer size when |
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using malloc. |
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A regression test was added to tst-sscanf. |
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--- glibc-2.17-c758a686/stdio-common/vfscanf.c 2012-12-24 22:02:13.000000000 -0500 |
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+++ glibc-2.17-c758a686/stdio-common/vfscanf.c 2015-05-28 14:01:58.512816390 -0400 |
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@@ -272,9 +272,10 @@ |
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if (__builtin_expect (wpsize == wpmax, 0)) \ |
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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 @@ |
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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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--- glibc-2.17-c758a686/stdio-common/tst-sscanf.c 2012-12-24 22:02:13.000000000 -0500 |
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+++ glibc-2.17-c758a686/stdio-common/tst-sscanf.c 2015-06-03 13:56:10.883924259 -0400 |
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@@ -196,5 +196,38 @@ |
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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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+ |
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+ |
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return result; |
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}
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