From 4d54424420c6300efbf57a7b9aa8635a8b8c1942 Mon Sep 17 00:00:00 2001 From: Paul Pluzhnikov Date: Fri, 6 Feb 2015 00:30:42 -0500 Subject: 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. (cherry picked from commit 5bd80bfe9ca0d955bfbbc002781bc7b01b6bcb06) Conflicts: ChangeLog NEWS --- ChangeLog | 8 ++++++++ NEWS | 9 +++++++-- stdio-common/tst-sscanf.c | 33 +++++++++++++++++++++++++++++++++ stdio-common/vfscanf.c | 12 ++++++------ 4 files changed, 54 insertions(+), 8 deletions(-) diff --git a/ChangeLog b/ChangeLog index a6461e6821..ccce486c9d 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2015-02-16 Paul Pluzhnikov + + [BZ #16618] + * stdio-common/tst-sscanf.c (main): Test for buffer overflow. + * stdio-common/vfscanf.c (_IO_vfscanf_internal): Compute needed + size in bytes. Store needed elements in wpmax. Use needed size + in bytes for extend_alloca. + 2015-02-16 H.J. Lu [BZ #17801] diff --git a/NEWS b/NEWS index 0eb3fb3e7f..976f2ea023 100644 --- a/NEWS +++ b/NEWS @@ -9,8 +9,13 @@ Version 2.20.1 * The following bugs are resolved with this release: - 16009, 16617, 17266, 17370, 17371, 17460, 17485, 17555, 17625, 17630, - 17801. + 16009, 16617, 16618, 17266, 17370, 17371, 17460, 17485, 17555, 17625, + 17630, 17801. + +* CVE-2015-1472 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. * CVE-2104-7817 The wordexp function could ignore the WRDE_NOCMD flag under certain input conditions resulting in the execution of a shell for diff --git a/stdio-common/tst-sscanf.c b/stdio-common/tst-sscanf.c index 9fef93a535..6394fe1ccc 100644 --- a/stdio-common/tst-sscanf.c +++ b/stdio-common/tst-sscanf.c @@ -233,5 +233,38 @@ main (void) } } + /* BZ #16618 + The test will segfault during SSCANF if the buffer overflow + is not fixed. The size of `s` is such that it forces the use + of malloc internally and this triggers the incorrect computation. + Thus the value for SIZE is arbitrariy high enough that malloc + is used. */ + { +#define SIZE 131072 + CHAR *s = malloc ((SIZE + 1) * sizeof (*s)); + if (s == NULL) + abort (); + for (size_t i = 0; i < SIZE; i++) + s[i] = L('0'); + s[SIZE] = L('\0'); + int i = 42; + /* Scan multi-digit zero into `i`. */ + if (SSCANF (s, L("%d"), &i) != 1) + { + printf ("FAIL: bug16618: SSCANF did not read one input item.\n"); + result = 1; + } + if (i != 0) + { + printf ("FAIL: bug16618: Value of `i` was not zero as expected.\n"); + result = 1; + } + free (s); + if (result != 1) + printf ("PASS: bug16618: Did not crash.\n"); +#undef SIZE + } + + return result; } diff --git a/stdio-common/vfscanf.c b/stdio-common/vfscanf.c index e0d224530c..a4f06b44e5 100644 --- a/stdio-common/vfscanf.c +++ b/stdio-common/vfscanf.c @@ -272,9 +272,10 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr, if (__glibc_unlikely (wpsize == wpmax)) \ { \ CHAR_T *old = wp; \ - size_t newsize = (UCHAR_MAX + 1 > 2 * wpmax \ - ? UCHAR_MAX + 1 : 2 * wpmax); \ - if (use_malloc || !__libc_use_alloca (newsize)) \ + bool fits = __glibc_likely (wpmax <= SIZE_MAX / sizeof (CHAR_T) / 2); \ + size_t wpneed = MAX (UCHAR_MAX + 1, 2 * wpmax); \ + size_t newsize = fits ? wpneed * sizeof (CHAR_T) : SIZE_MAX; \ + if (!__libc_use_alloca (newsize)) \ { \ wp = realloc (use_malloc ? wp : NULL, newsize); \ if (wp == NULL) \ @@ -286,14 +287,13 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr, } \ if (! use_malloc) \ MEMCPY (wp, old, wpsize); \ - wpmax = newsize; \ + wpmax = wpneed; \ use_malloc = true; \ } \ else \ { \ size_t s = wpmax * sizeof (CHAR_T); \ - wp = (CHAR_T *) extend_alloca (wp, s, \ - newsize * sizeof (CHAR_T)); \ + wp = (CHAR_T *) extend_alloca (wp, s, newsize); \ wpmax = s / sizeof (CHAR_T); \ if (old != NULL) \ MEMCPY (wp, old, wpsize); \ -- cgit 1.4.1