From: Florian Weimer Date: Fri, 1 Jun 2018 08:41:03 +0000 (+0200) Subject: libio: Avoid _allocate_buffer, _free_buffer function pointers [BZ #23236] X-Git-Tag: glibc-2.28~240 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4e8a6346cd3da2d88bbad745a1769260d36f2783;p=thirdparty%2Fglibc.git libio: Avoid _allocate_buffer, _free_buffer function pointers [BZ #23236] These unmangled function pointers reside on the heap and could be targeted by exploit writers, effectively bypassing libio vtable validation. Instead, we ignore these pointers and always call malloc or free. In theory, this is a backwards-incompatible change, but using the global heap instead of the user-supplied callback functions should have little application impact. (The old libstdc++ implementation exposed this functionality via a public, undocumented constructor in its strstreambuf class.) --- diff --git a/ChangeLog b/ChangeLog index 74588dac11f..1b5b27ce4b2 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,27 @@ +2018-06-01 Florian Weimer + + [BZ #23236] + * libio/strfile.h (struct _IO_str_fields): Rename members to + discourage their use and add comment. + (_IO_STR_DYNAMIC): Remove unused macro. + * libio/strops.c (_IO_str_init_static_internal): Do not use + callback pointers. Call malloc and free. + (_IO_str_overflow): Do not use callback pointers. Call malloc + and free. + (enlarge_userbuf): Likewise. + (_IO_str_finish): Call free. + * libio/wstrops.c (_IO_wstr_init_static): Initialize + _allocate_buffer_unused. + (_IO_wstr_overflow): Do not use callback pointers. Call malloc + and free. + (enlarge_userbuf): Likewise. + (_IO_wstr_finish): Call free. + * debug/vasprintf_chk.c (__vasprintf_chk): Initialize + _allocate_buffer_unused, _free_buffer_unused. + * libio/memstream.c (__open_memstream): Likewise. + * libio/vasprintf.c (_IO_vasprintf): Likewise. + * libio/wmemstream.c (open_wmemstream): Likewise. + 2018-05-30 Paul Pluzhnikov * sysdeps/x86_64/fpu/libm-test-ulps (log_vlen8_avx2): Update for diff --git a/debug/vasprintf_chk.c b/debug/vasprintf_chk.c index 46603d95388..48b4741651c 100644 --- a/debug/vasprintf_chk.c +++ b/debug/vasprintf_chk.c @@ -55,8 +55,8 @@ __vasprintf_chk (char **result_ptr, int flags, const char *format, _IO_JUMPS (&sf._sbf) = &_IO_str_jumps; _IO_str_init_static_internal (&sf, string, init_string_size, string); sf._sbf._f._flags &= ~_IO_USER_BUF; - sf._s._allocate_buffer = (_IO_alloc_type) malloc; - sf._s._free_buffer = (_IO_free_type) free; + sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc; + sf._s._free_buffer_unused = (_IO_free_type) free; /* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n can only come from read-only format strings. */ diff --git a/libio/memstream.c b/libio/memstream.c index 8d2726dea32..b5eaa5476c8 100644 --- a/libio/memstream.c +++ b/libio/memstream.c @@ -90,8 +90,8 @@ __open_memstream (char **bufloc, size_t *sizeloc) _IO_JUMPS_FILE_plus (&new_f->fp._sf._sbf) = &_IO_mem_jumps; _IO_str_init_static_internal (&new_f->fp._sf, buf, BUFSIZ, buf); new_f->fp._sf._sbf._f._flags &= ~_IO_USER_BUF; - new_f->fp._sf._s._allocate_buffer = (_IO_alloc_type) malloc; - new_f->fp._sf._s._free_buffer = (_IO_free_type) free; + new_f->fp._sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc; + new_f->fp._sf._s._free_buffer_unused = (_IO_free_type) free; new_f->fp.bufloc = bufloc; new_f->fp.sizeloc = sizeloc; diff --git a/libio/strfile.h b/libio/strfile.h index 46ac81809a3..75caac2af5f 100644 --- a/libio/strfile.h +++ b/libio/strfile.h @@ -32,8 +32,11 @@ typedef void (*_IO_free_type) (void*); struct _IO_str_fields { - _IO_alloc_type _allocate_buffer; - _IO_free_type _free_buffer; + /* These members are preserved for ABI compatibility. The glibc + implementation always calls malloc/free for user buffers if + _IO_USER_BUF or _IO_FLAGS2_USER_WBUF are not set. */ + _IO_alloc_type _allocate_buffer_unused; + _IO_free_type _free_buffer_unused; }; /* This is needed for the Irix6 N32 ABI, which has a 64 bit off_t type, @@ -53,10 +56,6 @@ typedef struct _IO_strfile_ struct _IO_str_fields _s; } _IO_strfile; -/* dynamic: set when the array object is allocated (or reallocated) as - necessary to hold a character sequence that can change in length. */ -#define _IO_STR_DYNAMIC(FP) ((FP)->_s._allocate_buffer != (_IO_alloc_type)0) - /* frozen: set when the program has requested that the array object not be altered, reallocated, or freed. */ #define _IO_STR_FROZEN(FP) ((FP)->_f._flags & _IO_USER_BUF) diff --git a/libio/strops.c b/libio/strops.c index eddd722c093..df8268b7abc 100644 --- a/libio/strops.c +++ b/libio/strops.c @@ -61,7 +61,7 @@ _IO_str_init_static_internal (_IO_strfile *sf, char *ptr, size_t size, fp->_IO_read_end = end; } /* A null _allocate_buffer function flags the strfile as being static. */ - sf->_s._allocate_buffer = (_IO_alloc_type) 0; + sf->_s._allocate_buffer_unused = (_IO_alloc_type) 0; } void @@ -103,8 +103,7 @@ _IO_str_overflow (FILE *fp, int c) size_t new_size = 2 * old_blen + 100; if (new_size < old_blen) return EOF; - new_buf - = (char *) (*((_IO_strfile *) fp)->_s._allocate_buffer) (new_size); + new_buf = malloc (new_size); if (new_buf == NULL) { /* __ferror(fp) = 1; */ @@ -113,7 +112,7 @@ _IO_str_overflow (FILE *fp, int c) if (old_buf) { memcpy (new_buf, old_buf, old_blen); - (*((_IO_strfile *) fp)->_s._free_buffer) (old_buf); + free (old_buf); /* Make sure _IO_setb won't try to delete _IO_buf_base. */ fp->_IO_buf_base = NULL; } @@ -182,15 +181,14 @@ enlarge_userbuf (FILE *fp, off64_t offset, int reading) size_t newsize = offset + 100; char *oldbuf = fp->_IO_buf_base; - char *newbuf - = (char *) (*((_IO_strfile *) fp)->_s._allocate_buffer) (newsize); + char *newbuf = malloc (newsize); if (newbuf == NULL) return 1; if (oldbuf != NULL) { memcpy (newbuf, oldbuf, _IO_blen (fp)); - (*((_IO_strfile *) fp)->_s._free_buffer) (oldbuf); + free (oldbuf); /* Make sure _IO_setb won't try to delete _IO_buf_base. */ fp->_IO_buf_base = NULL; @@ -346,7 +344,7 @@ void _IO_str_finish (FILE *fp, int dummy) { if (fp->_IO_buf_base && !(fp->_flags & _IO_USER_BUF)) - (((_IO_strfile *) fp)->_s._free_buffer) (fp->_IO_buf_base); + free (fp->_IO_buf_base); fp->_IO_buf_base = NULL; _IO_default_finish (fp, 0); diff --git a/libio/vasprintf.c b/libio/vasprintf.c index 08218ddbe76..6c35d2b1088 100644 --- a/libio/vasprintf.c +++ b/libio/vasprintf.c @@ -54,8 +54,8 @@ _IO_vasprintf (char **result_ptr, const char *format, va_list args) _IO_JUMPS (&sf._sbf) = &_IO_str_jumps; _IO_str_init_static_internal (&sf, string, init_string_size, string); sf._sbf._f._flags &= ~_IO_USER_BUF; - sf._s._allocate_buffer = (_IO_alloc_type) malloc; - sf._s._free_buffer = (_IO_free_type) free; + sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc; + sf._s._free_buffer_unused = (_IO_free_type) free; ret = _IO_vfprintf (&sf._sbf._f, format, args); if (ret < 0) { diff --git a/libio/wmemstream.c b/libio/wmemstream.c index 88044f31500..c92d2da4b29 100644 --- a/libio/wmemstream.c +++ b/libio/wmemstream.c @@ -92,8 +92,8 @@ open_wmemstream (wchar_t **bufloc, size_t *sizeloc) _IO_wstr_init_static (&new_f->fp._sf._sbf._f, buf, BUFSIZ / sizeof (wchar_t), buf); new_f->fp._sf._sbf._f._flags2 &= ~_IO_FLAGS2_USER_WBUF; - new_f->fp._sf._s._allocate_buffer = (_IO_alloc_type) malloc; - new_f->fp._sf._s._free_buffer = (_IO_free_type) free; + new_f->fp._sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc; + new_f->fp._sf._s._free_buffer_unused = (_IO_free_type) free; new_f->fp.bufloc = bufloc; new_f->fp.sizeloc = sizeloc; diff --git a/libio/wstrops.c b/libio/wstrops.c index 36e8b20fefc..6626f2f7116 100644 --- a/libio/wstrops.c +++ b/libio/wstrops.c @@ -63,7 +63,7 @@ _IO_wstr_init_static (FILE *fp, wchar_t *ptr, size_t size, fp->_wide_data->_IO_read_end = end; } /* A null _allocate_buffer function flags the strfile as being static. */ - (((_IO_strfile *) fp)->_s._allocate_buffer) = (_IO_alloc_type)0; + (((_IO_strfile *) fp)->_s._allocate_buffer_unused) = (_IO_alloc_type)0; } wint_t @@ -95,9 +95,7 @@ _IO_wstr_overflow (FILE *fp, wint_t c) || __glibc_unlikely (new_size > SIZE_MAX / sizeof (wchar_t))) return EOF; - new_buf - = (wchar_t *) (*((_IO_strfile *) fp)->_s._allocate_buffer) (new_size - * sizeof (wchar_t)); + new_buf = malloc (new_size * sizeof (wchar_t)); if (new_buf == NULL) { /* __ferror(fp) = 1; */ @@ -106,7 +104,7 @@ _IO_wstr_overflow (FILE *fp, wint_t c) if (old_buf) { __wmemcpy (new_buf, old_buf, old_wblen); - (*((_IO_strfile *) fp)->_s._free_buffer) (old_buf); + free (old_buf); /* Make sure _IO_setb won't try to delete _IO_buf_base. */ fp->_wide_data->_IO_buf_base = NULL; } @@ -186,16 +184,14 @@ enlarge_userbuf (FILE *fp, off64_t offset, int reading) return 1; wchar_t *oldbuf = wd->_IO_buf_base; - wchar_t *newbuf - = (wchar_t *) (*((_IO_strfile *) fp)->_s._allocate_buffer) (newsize - * sizeof (wchar_t)); + wchar_t *newbuf = malloc (newsize * sizeof (wchar_t)); if (newbuf == NULL) return 1; if (oldbuf != NULL) { __wmemcpy (newbuf, oldbuf, _IO_wblen (fp)); - (*((_IO_strfile *) fp)->_s._free_buffer) (oldbuf); + free (oldbuf); /* Make sure _IO_setb won't try to delete _IO_buf_base. */ wd->_IO_buf_base = NULL; @@ -357,7 +353,7 @@ void _IO_wstr_finish (FILE *fp, int dummy) { if (fp->_wide_data->_IO_buf_base && !(fp->_flags2 & _IO_FLAGS2_USER_WBUF)) - (((_IO_strfile *) fp)->_s._free_buffer) (fp->_wide_data->_IO_buf_base); + free (fp->_wide_data->_IO_buf_base); fp->_wide_data->_IO_buf_base = NULL; _IO_wdefault_finish (fp, 0);