aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorFlorian Weimer <fweimer@redhat.com>2018-06-01 10:41:03 +0200
committerFlorian Weimer <fweimer@redhat.com>2018-06-01 10:41:03 +0200
commit4e8a6346cd3da2d88bbad745a1769260d36f2783 (patch)
treedcf9deeedd5263469fa425574c0ac671a8b43c2a
parent50d004c91c942221b862a4a13a4b5f78cfb0d595 (diff)
downloadglibc-4e8a6346cd3da2d88bbad745a1769260d36f2783.tar
glibc-4e8a6346cd3da2d88bbad745a1769260d36f2783.tar.gz
glibc-4e8a6346cd3da2d88bbad745a1769260d36f2783.tar.bz2
glibc-4e8a6346cd3da2d88bbad745a1769260d36f2783.zip
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.)
-rw-r--r--ChangeLog24
-rw-r--r--debug/vasprintf_chk.c4
-rw-r--r--libio/memstream.c4
-rw-r--r--libio/strfile.h11
-rw-r--r--libio/strops.c14
-rw-r--r--libio/vasprintf.c4
-rw-r--r--libio/wmemstream.c4
-rw-r--r--libio/wstrops.c16
8 files changed, 49 insertions, 32 deletions
diff --git a/ChangeLog b/ChangeLog
index 74588dac11..1b5b27ce4b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,27 @@
+2018-06-01 Florian Weimer <fweimer@redhat.com>
+
+ [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 <ppluzhnikov@google.com>
* 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 46603d9538..48b4741651 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 8d2726dea3..b5eaa5476c 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 46ac81809a..75caac2af5 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 eddd722c09..df8268b7ab 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 08218ddbe7..6c35d2b108 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 88044f3150..c92d2da4b2 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 36e8b20fef..6626f2f711 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);