From: Jeremy Fitzhardinge <[email protected]>
This change allows callers to use a 0-byte buffer and a NULL buffer
pointer with vsnprintf, so it can be used to determine how large the
resulting formatted string will be.
Previously the code effectively treated a size of 0 as a size of 4G (on
32-bit systems), with other checks preventing it from actually trying to
emit the string - but the terminal \0 would still be written, which
would crash if the buffer is NULL.
This change changes the boundary check so that 'end' points to the
putative location of the terminal '\0', which is only written if size > 0.
vsnprintf still allows the buffer size to be set very large, to allow
unbounded buffer sizes (to implement sprintf, etc).
Signed-off-by: Jeremy Fitzhardinge <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
lib/vsprintf.c | 67 ++++++++++++++++++++++++++++----------------------------
1 file changed, 34 insertions(+), 33 deletions(-)
diff -r 509769aa6636 lib/vsprintf.c
--- a/lib/vsprintf.c Tue Jun 20 16:40:33 2006 -0700
+++ b/lib/vsprintf.c Tue Jun 20 16:47:51 2006 -0700
@@ -187,49 +187,49 @@ static char * number(char * buf, char *
size -= precision;
if (!(type&(ZEROPAD+LEFT))) {
while(size-->0) {
- if (buf <= end)
+ if (buf < end)
*buf = ' ';
++buf;
}
}
if (sign) {
- if (buf <= end)
+ if (buf < end)
*buf = sign;
++buf;
}
if (type & SPECIAL) {
if (base==8) {
- if (buf <= end)
+ if (buf < end)
*buf = '0';
++buf;
} else if (base==16) {
- if (buf <= end)
+ if (buf < end)
*buf = '0';
++buf;
- if (buf <= end)
+ if (buf < end)
*buf = digits[33];
++buf;
}
}
if (!(type & LEFT)) {
while (size-- > 0) {
- if (buf <= end)
+ if (buf < end)
*buf = c;
++buf;
}
}
while (i < precision--) {
- if (buf <= end)
+ if (buf < end)
*buf = '0';
++buf;
}
while (i-- > 0) {
- if (buf <= end)
+ if (buf < end)
*buf = tmp[i];
++buf;
}
while (size-- > 0) {
- if (buf <= end)
+ if (buf < end)
*buf = ' ';
++buf;
}
@@ -272,7 +272,8 @@ int vsnprintf(char *buf, size_t size, co
/* 'z' changed to 'Z' --davidm 1/25/99 */
/* 't' added for ptrdiff_t */
- /* Reject out-of-range values early */
+ /* Reject out-of-range values early. Large positive sizes are
+ used for unknown buffer sizes. */
if (unlikely((int) size < 0)) {
/* There can be only one.. */
static int warn = 1;
@@ -282,16 +283,17 @@ int vsnprintf(char *buf, size_t size, co
}
str = buf;
- end = buf + size - 1;
-
- if (end < buf - 1) {
- end = ((void *) -1);
- size = end - buf + 1;
+ end = buf + size;
+
+ /* Make sure end is always >= buf */
+ if (end < buf) {
+ end = ((void *) ~0ull);
+ size = end - buf;
}
for (; *fmt ; ++fmt) {
if (*fmt != '%') {
- if (str <= end)
+ if (str < end)
*str = *fmt;
++str;
continue;
@@ -357,17 +359,17 @@ int vsnprintf(char *buf, size_t size, co
case 'c':
if (!(flags & LEFT)) {
while (--field_width > 0) {
- if (str <= end)
+ if (str < end)
*str = ' ';
++str;
}
}
c = (unsigned char) va_arg(args, int);
- if (str <= end)
+ if (str < end)
*str = c;
++str;
while (--field_width > 0) {
- if (str <= end)
+ if (str < end)
*str = ' ';
++str;
}
@@ -382,18 +384,18 @@ int vsnprintf(char *buf, size_t size, co
if (!(flags & LEFT)) {
while (len < field_width--) {
- if (str <= end)
+ if (str < end)
*str = ' ';
++str;
}
}
for (i = 0; i < len; ++i) {
- if (str <= end)
+ if (str < end)
*str = *s;
++str; ++s;
}
while (len < field_width--) {
- if (str <= end)
+ if (str < end)
*str = ' ';
++str;
}
@@ -426,7 +428,7 @@ int vsnprintf(char *buf, size_t size, co
continue;
case '%':
- if (str <= end)
+ if (str < end)
*str = '%';
++str;
continue;
@@ -449,11 +451,11 @@ int vsnprintf(char *buf, size_t size, co
break;
default:
- if (str <= end)
+ if (str < end)
*str = '%';
++str;
if (*fmt) {
- if (str <= end)
+ if (str < end)
*str = *fmt;
++str;
} else {
@@ -483,14 +485,13 @@ int vsnprintf(char *buf, size_t size, co
str = number(str, end, num, base,
field_width, precision, flags);
}
- if (str <= end)
- *str = '\0';
- else if (size > 0)
- /* don't write out a null byte if the buf size is zero */
- *end = '\0';
- /* the trailing null byte doesn't count towards the total
- * ++str;
- */
+ if (size > 0) {
+ if (str < end)
+ *str = '\0';
+ else
+ *end = '\0';
+ }
+ /* the trailing null byte doesn't count towards the total */
return str-buf;
}
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
