From 47cb886328acf41612165a93e05af3db3d20ee17 Mon Sep 17 00:00:00 2001 From: Paul Pluzhnikov Date: Fri, 6 Feb 2015 00:30:42 -0500 Subject: [PATCH] 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. Conflicts: ChangeLog NEWS --- ChangeLog | 8 ++++++++ NEWS | 2 +- stdio-common/tst-sscanf.c | 33 +++++++++++++++++++++++++++++++++ stdio-common/vfscanf.c | 12 ++++++------ 4 files changed, 48 insertions(+), 7 deletions(-) diff --git a/ChangeLog b/ChangeLog index 3e91cf1ea5..a7b9df12dc 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2015-02-23 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. + 2015-02-12 Adhemerval Zanella * sysdeps/unix/sysv/linux/powerpc/htm.h [TABORT]: Fix encoding for diff --git a/NEWS b/NEWS index 46f6d9de47..4f7d68f696 100644 --- a/NEWS +++ b/NEWS @@ -9,7 +9,7 @@ Version 2.20.1 * The following bugs are resolved with this release: - 16617, 17266, 17370, 17371, 17625, 17630. + 16617, 16618, 17266, 17370, 17371, 17625, 17630. * Added support for TSX lock elision of pthread mutexes on powerpc32, powerpc64 and powerpc64le. This may improve lock scaling of existing programs on 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); \ -- 2.11.4.GIT