Fix open mode for IOCTLs which write to the tape.

1 files changed, 15 insertions, 2 deletions

diff --git a/miscutils/mt.c b/miscutils/mt.c
index 250856f05..cd926272e 100644
--- a/miscutils/mt.c
+++ b/miscutils/mt.c
@@ -55,7 +55,7 @@ extern int mt_main(int argc, char **argv)
         const char *file = "/dev/tape";
         const struct mt_opcodes *code = opcodes;
         struct mtop op;
-        int fd;
+        int fd, mode;
         
         if (argc < 2) {
                 show_usage();
@@ -87,7 +87,20 @@ extern int mt_main(int argc, char **argv)
         else
                 op.mt_count = 1;                /* One, not zero, right? */
 
-        if ((fd = open(file, O_RDONLY, 0)) < 0)
+        switch (code->value) {
+                case MTWEOF:
+                case MTERASE:
+                case MTWSM:
+                case MTSETDRVBUFFER:
+                        mode = O_WRONLY;
+                        break;
+
+                default:
+                        mode = O_RDONLY;
+                        break;
+        }
+
+        if ((fd = open(file, mode, 0)) < 0)
                 perror_msg_and_die("%s", file);
 
         if (ioctl(fd, MTIOCTOP, &op) != 0)