Fix minor fallout from sysctl strings being nulterminated now. The dmesg

code can read the buffer via sysctl or from a core file.  In the core file
case there will be no nulterm, and the code copes with that, but now in the
sysctl case there is a nulterm (there didn't used to be).  The least
disruptive way to restore the old behavior (and eliminate a spurious '\000'
at the end of the output) is to remove the nulterm (by decrementing the
buffer length) in the sysctl case.

1 files changed, 6 insertions, 2 deletions

diff --git a/sbin/dmesg/dmesg.c b/sbin/dmesg/dmesg.c
index f0fcb81..9fee416 100644
--- a/sbin/dmesg/dmesg.c
+++ b/sbin/dmesg/dmesg.c
@@ -111,8 +111,10 @@ main(int argc, char *argv[])
 
 	if (memf == NULL) {
 		/*
-		 * Running kernel.  Use sysctl.  This gives an unwrapped
-		 * buffer as a side effect.
+		 * Running kernel.  Use sysctl.  This gives an unwrapped buffer
+		 * as a side effect.  Remove nulterm (if present) so the value
+		 * returned by sysctl is formatted as the rest of the code
+		 * expects (the same as the value read from a core file below).
 		 */
 		if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
 			err(1, "sysctl kern.msgbuf");
@@ -120,6 +122,8 @@ main(int argc, char *argv[])
 			errx(1, "malloc failed");
 		if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
 			err(1, "sysctl kern.msgbuf");
+		if (buflen > 0 && bp[buflen - 1] == '\0')
+			buflen--;
 		if (clear)
 			if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int)))
 				err(1, "sysctl kern.msgbuf_clear");