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Re: vfprintf typing problem
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 30 Mar 2012 22:13:01 -0700
> Thanks for hacking on this. Some further comments:
Sorry for taking so long to follow up, I thought that iconvdata
regression introduced yesterday was caused by these changes :-/
> On 03/30/2012 07:59 PM, David Miller wrote:
>> + if (__builtin_expect ((unsigned int) INT_MAX - (unsigned int) done \
>> + < (Len), 0)) \
>
> The two casts to 'unsigned int' aren't needed and should be removed.
Ok, makes sense.
> Also, because read_int does not check for overflow, a large width or
> precision might be treated incorrectly, because read_int might return
> (say) 1 even if the integer has overflowed.
Right.
> So I suggest the following fixes in this area:
>
> * Change read_int to return 'int', not 'unsigned'.
>
> * Have read_int check for overflow and return -1 if it occurs.
>
> * Change all read_int callers to do the right thing when read_int
> returns -1.
Done.
2012-03-30 David S. Miller <davem@davemloft.net>
* stdio-common/printf-parse.h (read_int): Change return type to
'int', return -1 on INT_MAX overflow.
* stdio-common/vfprintf.c (vfprintf): Validate width and precision
against overflow of INT_MAX. Set errno to EOVERFLOW when 'done'
overflows INT_MAX. Check for overflow of in-format-string precision
values properly.
* stdio-common/bug22.c: Adjust to test both width/prevision
INT_MAX overflow as well as total length INT_MAX overflow. Check
explicitly for proper errno values.
diff --git a/stdio-common/bug22.c b/stdio-common/bug22.c
index 2228388..cb99dfe 100644
--- a/stdio-common/bug22.c
+++ b/stdio-common/bug22.c
@@ -1,12 +1,22 @@
/* BZ #5424 */
#include <stdio.h>
+#include <errno.h>
+/* INT_MAX + 1 */
#define N 2147483648
+/* (INT_MAX / 2) + 2 */
+#define N2 1073741825
+
+/* INT_MAX - 3 */
+#define N3 2147483644
+
#define STRINGIFY(S) #S
#define MAKE_STR(S) STRINGIFY(S)
#define SN MAKE_STR(N)
+#define SN2 MAKE_STR(N2)
+#define SN3 MAKE_STR(N3)
static int
do_test (void)
@@ -20,11 +30,25 @@ do_test (void)
return 1;
}
- ret = fprintf (fp, "%" SN "d%" SN "d", 1, 1);
+ ret = fprintf (fp, "%" SN "d", 1);
+ printf ("ret = %d\n", ret);
+ if (ret != -1 || errno != ERANGE)
+ return 1;
+
+ ret = fprintf (fp, "%." SN "d", 1);
+ printf ("ret = %d\n", ret);
+ if (ret != -1 || errno != ERANGE)
+ return 1;
+
+ ret = fprintf (fp, "%." SN3 "d", 1);
+ printf ("ret = %d\n", ret);
+ if (ret != -1 || errno != ERANGE)
+ return 1;
+ ret = fprintf (fp, "%" SN2 "d%" SN2 "d", 1, 1);
printf ("ret = %d\n", ret);
- return ret != -1;
+ return ret != -1 || errno != EOVERFLOW;
}
#define TIMEOUT 30
diff --git a/stdio-common/printf-parse.h b/stdio-common/printf-parse.h
index 72665dc..eb2d628 100644
--- a/stdio-common/printf-parse.h
+++ b/stdio-common/printf-parse.h
@@ -68,7 +68,7 @@ union printf_arg
#ifndef DONT_NEED_READ_INT
/* Read a simple integer from a string and update the string pointer.
It is assumed that the first character is a digit. */
-static unsigned int
+static int
read_int (const UCHAR_T * *pstr)
{
unsigned int retval = **pstr - L_('0');
@@ -77,9 +77,11 @@ read_int (const UCHAR_T * *pstr)
{
retval *= 10;
retval += **pstr - L_('0');
+ if (retval > INT_MAX)
+ return -1;
}
- return retval;
+ return (int) retval;
}
#endif
diff --git a/stdio-common/vfprintf.c b/stdio-common/vfprintf.c
index 1e90483..4287291 100644
--- a/stdio-common/vfprintf.c
+++ b/stdio-common/vfprintf.c
@@ -67,10 +67,10 @@
do { \
unsigned int _val = val; \
assert ((unsigned int) done < (unsigned int) INT_MAX); \
- if (__builtin_expect ((unsigned int) INT_MAX - (unsigned int) done \
- < _val, 0)) \
+ if (__builtin_expect (INT_MAX - done < _val, 0)) \
{ \
done = -1; \
+ __set_errno (EOVERFLOW); \
goto all_done; \
} \
done += _val; \
@@ -141,12 +141,17 @@
do \
{ \
assert ((size_t) done <= (size_t) INT_MAX); \
- if ((size_t) PUT (s, (String), (Len)) != (size_t) (Len) \
- || (size_t) INT_MAX - (size_t) done < (size_t) (Len)) \
+ if ((size_t) PUT (s, (String), (Len)) != (size_t) (Len)) \
{ \
done = -1; \
goto all_done; \
} \
+ if (__builtin_expect (INT_MAX - done < (Len), 0)) \
+ { \
+ done = -1; \
+ __set_errno (EOVERFLOW); \
+ goto all_done; \
+ } \
done += (Len); \
} \
while (0)
@@ -1449,7 +1454,7 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap)
left = 1;
}
- if (__builtin_expect (width >= (size_t) -1 / sizeof (CHAR_T) - 32, 0))
+ if (__builtin_expect (width >= INT_MAX / sizeof (CHAR_T) - 32, 0))
{
__set_errno (ERANGE);
done = -1;
@@ -1481,7 +1486,8 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap)
LABEL (width):
width = read_int (&f);
- if (__builtin_expect (width >= (size_t) -1 / sizeof (CHAR_T) - 32, 0))
+ if (__builtin_expect (width == -1
+ || width >= INT_MAX / sizeof (CHAR_T) - 32, 0))
{
__set_errno (ERANGE);
done = -1;
@@ -1529,13 +1535,24 @@ vfprintf (FILE *s, const CHAR_T *format, va_list ap)
prec = -1;
}
else if (ISDIGIT (*f))
- prec = read_int (&f);
+ {
+ prec = read_int (&f);
+
+ /* The precision was specified in this case as an extremely
+ large positive value. */
+ if (prec == -1)
+ {
+ __set_errno (ERANGE);
+ done = -1;
+ goto all_done;
+ }
+ }
else
prec = 0;
if (prec > width
&& prec > sizeof (work_buffer) / sizeof (work_buffer[0]) - 32)
{
- if (__builtin_expect (prec >= (size_t) -1 / sizeof (CHAR_T) - 32, 0))
+ if (__builtin_expect (prec >= INT_MAX / sizeof (CHAR_T) - 32, 0))
{
__set_errno (ERANGE);
done = -1;