kernel/sysctl.c: check return value after call proc_put_char() in __do_proc_doulongvec_minmax()

Need to check the return value of proc_put_char(), as was done in
__do_proc_doulongvec_minmax().
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/sysctl.c

@@ -2222,8 +2222,11 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
 			*i = val;
 		} else {
 			val = convdiv * (*i) / convmul;
-			if (!first)
+			if (!first) {
 				err = proc_put_char(&buffer, &left, '\t');
+				if (err)
+					break;
+			}
 			err = proc_put_long(&buffer, &left, val, false);
 			if (err)
 				break;