This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
[PATCH] vfscanf: Avoid multiple reads of multi-byte character width
- From: fweimer at redhat dot com (Florian Weimer)
- To: libc-alpha at sourceware dot org
- Date: Fri, 02 Sep 2016 15:19:53 +0200
- Subject: [PATCH] vfscanf: Avoid multiple reads of multi-byte character width
- Authentication-results: sourceware.org; auth=none
This avoids a race condition if the process-global locale is changed
while vfscanf is running. MB_LEN_MAX is always larger than MB_CUR_MAX,
so we might realloc earlier than necessary (but even MB_CUR_MAX could
be larger than the minimum required space).
The existing length was a bit questionable because str + MB_LEN_MAX
might point past the end of the buffer.
2016-09-02 Florian Weimer <fweimer@redhat.com>
* stdio-common/vfscanf.c (_IO_vfwscanf): Use MB_LEN_MAX instead of
MB_CUR_MAX to avoid race condition. Avoid pointer arithmetic
outside of allocated array.
diff --git a/stdio-common/vfscanf.c b/stdio-common/vfscanf.c
index 8cd5955..2b7093e 100644
--- a/stdio-common/vfscanf.c
+++ b/stdio-common/vfscanf.c
@@ -757,7 +757,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
size_t n;
if (!(flags & SUPPRESS) && (flags & POSIX_MALLOC)
- && str + MB_CUR_MAX >= *strptr + strsize)
+ && MB_LEN_MAX >= *strptr + strsize - str)
{
/* We have to enlarge the buffer if the `m' flag
was given. */
@@ -769,7 +769,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
{
/* Can't allocate that much. Last-ditch effort. */
newstr = (char *) realloc (*strptr,
- strleng + MB_CUR_MAX);
+ strleng + MB_LEN_MAX);
if (newstr == NULL)
{
/* c can't have `a' flag, only `m'. */
@@ -780,7 +780,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
{
*strptr = newstr;
str = newstr + strleng;
- strsize = strleng + MB_CUR_MAX;
+ strsize = strleng + MB_LEN_MAX;
}
}
else
@@ -1048,7 +1048,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
size_t n;
if (!(flags & SUPPRESS) && (flags & MALLOC)
- && str + MB_CUR_MAX >= *strptr + strsize)
+ && MB_LEN_MAX >= *strptr + strsize - str)
{
/* We have to enlarge the buffer if the `a' or `m'
flag was given. */
@@ -1061,7 +1061,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
/* Can't allocate that much. Last-ditch
effort. */
newstr = (char *) realloc (*strptr,
- strleng + MB_CUR_MAX);
+ strleng + MB_LEN_MAX);
if (newstr == NULL)
{
if (flags & POSIX_MALLOC)
@@ -1081,7 +1081,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
{
*strptr = newstr;
str = newstr + strleng;
- strsize = strleng + MB_CUR_MAX;
+ strsize = strleng + MB_LEN_MAX;
}
}
else
@@ -1097,7 +1097,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
if (__glibc_unlikely (n == (size_t) -1))
encode_error ();
- assert (n <= MB_CUR_MAX);
+ assert (n <= MB_LEN_MAX);
str += n;
}
#else
@@ -2675,7 +2675,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
/* Possibly correct character, just not enough
input. */
++cnt;
- assert (cnt < MB_CUR_MAX);
+ assert (cnt < MB_LEN_MAX);
continue;
}
cnt = 0;
@@ -2827,7 +2827,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
if (!(flags & SUPPRESS))
{
if ((flags & MALLOC)
- && str + MB_CUR_MAX >= *strptr + strsize)
+ && MB_LEN_MAX >= *strptr + strsize - str)
{
/* Enlarge the buffer. */
size_t strleng = str - *strptr;
@@ -2839,7 +2839,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
/* Can't allocate that much. Last-ditch
effort. */
newstr = (char *) realloc (*strptr,
- strleng + MB_CUR_MAX);
+ strleng + MB_LEN_MAX);
if (newstr == NULL)
{
if (flags & POSIX_MALLOC)
@@ -2859,7 +2859,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
{
*strptr = newstr;
str = newstr + strleng;
- strsize = strleng + MB_CUR_MAX;
+ strsize = strleng + MB_LEN_MAX;
}
}
else
@@ -2875,7 +2875,7 @@ _IO_vfscanf_internal (_IO_FILE *s, const char *format, _IO_va_list argptr,
if (__glibc_unlikely (n == (size_t) -1))
encode_error ();
- assert (n <= MB_CUR_MAX);
+ assert (n <= MB_LEN_MAX);
str += n;
}
while (--width > 0 && inchar () != WEOF);