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authorJeremy Fitzhardinge <jeremy@xensource.com>2006-06-25 05:49:17 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-25 10:01:23 -0700
commitf796937a062c7aeb44cd0e75e1586c8543634a7d (patch)
treec3cfcbb27e291621e31cff71288f3e82d8b149a8
parent891c668b90ded38cec36f0852c4983573597170d (diff)
[PATCH] Fix bounds check in vsnprintf, to allow for a 0 size and NULL buffer
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). [akpm@osdl.org: fix long-vs-longlong confusion] Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--lib/vsprintf.c65
1 files changed, 33 insertions, 32 deletions
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index b07db5ca3f6..f5959476e53 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -187,49 +187,49 @@ static char * number(char * buf, char * end, unsigned long long num, int base, i
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, const char *fmt, va_list args)
/* '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, const char *fmt, va_list args)
}
str = buf;
- end = buf + size - 1;
+ end = buf + size;
- if (end < buf - 1) {
- end = ((void *) -1);
- size = end - buf + 1;
+ /* Make sure end is always >= buf */
+ if (end < buf) {
+ end = ((void *)-1);
+ 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, const char *fmt, va_list args)
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, const char *fmt, va_list args)
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, const char *fmt, va_list args)
continue;
case '%':
- if (str <= end)
+ if (str < end)
*str = '%';
++str;
continue;
@@ -449,11 +451,11 @@ int vsnprintf(char *buf, size_t size, const char *fmt, va_list args)
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, const char *fmt, va_list args)
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;
}