Date: Wed, 4 Nov 1998 19:17:23 -0800 (PST) From: Archie Cobbs <archie@whistle.com> To: FreeBSD-gnats-submit@FreeBSD.ORG Subject: kern/8577: Request [v]snprintf() in the kernel Message-ID: <199811050317.TAA03886@bubba.whistle.com>
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>Number: 8577
>Category: kern
>Synopsis: Request [v]snprintf() in the kernel
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: change-request
>Submitter-Id: current-users
>Arrival-Date: Wed Nov 4 19:20:00 PST 1998
>Last-Modified:
>Originator: Archie Cobbs
>Organization:
Whistle Communications, Inc.
>Release: FreeBSD 2.2.6-RELEASE i386
>Environment:
FreeBSD 3.0-current
>Description:
Request that snprintf() and vsnprintf() functions
be added to the kernel. This would enable us to change
kernel code that uses sprintf() for:
- Greater safety from buffer overflows
- Eliminate code that does manual bounds checking,
ie, the equivalent of what snprintf() does automatically
Also, the amount of code to add to the kernel is just
a few lines.
>How-To-Repeat:
>Fix:
This patch is a start.. it enable the aforementioned cleanups
to start happening.
Index: kern/subr_prf.c
===================================================================
RCS file: /cvs/freebsd/src/sys/kern/subr_prf.c,v
retrieving revision 1.50
diff -u -r1.50 subr_prf.c
--- subr_prf.c 1998/09/06 06:25:04 1.50
+++ subr_prf.c 1998/11/05 03:10:12
@@ -68,6 +68,8 @@
struct putchar_arg {int flags; struct tty *tty; };
static void putchar __P((int ch, void *arg));
static char *ksprintn __P((u_long num, int base, int *len));
+static void snprintf_func __P((int ch, void *arg));
+struct snprintf_arg { char *buf; size_t remain; };
static int consintr = 1; /* Ok to handle console interrupts? */
static int msgbufmapped; /* Set when safe to use msgbuf */
@@ -326,6 +328,47 @@
retval = kvprintf(cfmt, NULL, (void *)buf, 10, ap);
buf[retval] = '\0';
return retval;
+}
+
+/*
+ * Scaled down version of snprintf(3).
+ */
+int
+snprintf(char *buf, size_t max, const char *cfmt, ...)
+{
+ int retval;
+ va_list ap;
+
+ va_start(ap, cfmt);
+ retval = vsnprintf(buf, max, cfmt, ap);
+ va_end(ap);
+ return retval;
+}
+
+/*
+ * Scaled down version of vsnprintf(3).
+ */
+int
+vsnprintf(char *buf, size_t size, const char *cfmt, va_list ap)
+{
+ struct snprintf_arg info = { buf, size };
+ int retval;
+
+ retval = kvprintf(cfmt, snprintf_func, &info, 10, ap);
+ if (info.remain >= 1)
+ *info.buf++ = '\0';
+ return retval;
+}
+
+static void
+snprintf_func(int ch, void *arg)
+{
+ struct snprintf_arg *const info = (struct snprintf_arg *) arg;
+
+ if (info->remain >= 2) {
+ *info->buf++ = ch;
+ info->remain--;
+ }
}
/*
Index: sys/systm.h
===================================================================
RCS file: /cvs/freebsd/src/sys/sys/systm.h,v
retrieving revision 1.78
diff -u -r1.78 systm.h
--- systm.h 1998/10/30 05:41:15 1.78
+++ systm.h 1998/11/05 03:10:13
@@ -108,6 +108,8 @@
void logwakeup __P((void));
int printf __P((const char *, ...)) __printflike(1, 2);
int sprintf __P((char *buf, const char *, ...)) __printflike(2, 3);
+int snprintf __P((char *, size_t, const char *, ...)) __printflike(3, 4);
+int vsnprintf __P((char *, size_t, const char *, _BSD_VA_LIST_)) __printflike(3, 0);
void uprintf __P((const char *, ...)) __printflike(1, 2);
void vprintf __P((const char *, _BSD_VA_LIST_)) __printflike(1, 0);
int vsprintf __P((char *buf, const char *, _BSD_VA_LIST_)) __printflike(2, 0);
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