Till Maas wrote:
> currently cryptsetup tries to detect whether or not a device is readonly
> with the BLKROGET ioctl call. This does not work for cdroms under linux. I
> do not know why and whether or not this is intended. The attached patch
> changes this. It makes cryptsetup try to open the devide Read-Write. When
> this fails and the error is EROFS, then it is assumed that the device is
> readonly and cryptsetup tries to open it read-only and proceeds as normal.
I modified the patch to also try BLKROGET, because it seems that read-only
loop devices (created with losetup -r) may still be opened. With this patch
cryptsetup first tries the method described above and in case this does not
return, that the device is read-only, it also tries BLKROGET.
Regards,
Till
--- cryptsetup-1.0.5.orig/lib/setup.c 2007-05-02 16:44:06.000000000 +0200
+++ cryptsetup-1.0.5/lib/setup.c 2007-08-17 19:18:31.000000000 +0200
@@ -318,11 +318,21 @@
char buf[128];
uint64_t size;
unsigned long size_small;
- int readonly;
+ int readonly = 0;
int ret = -1;
int fd;
- fd = open(device, O_RDONLY);
+ /* Try to open read-write to check whether it is a read-only device */
+ fd = open(device, O_RDWR);
+ if (fd < 0) {
+ if (errno == EROFS) {
+ readonly = 1;
+ fd = open(device, O_RDONLY);
+ }
+ } else {
+ close(fd);
+ fd = open(device, O_RDONLY);
+ }
if (fd < 0) {
set_error("Error opening device: %s",
strerror_r(errno, buf, 128));
@@ -330,13 +340,19 @@
}
#ifdef BLKROGET
- if (ioctl(fd, BLKROGET, &readonly) < 0) {
- set_error("BLKROGET failed on device: %s",
- strerror_r(errno, buf, 128));
- return -1;
+ /* If the device can be opened read-write, i.e. readonly is still 0, then
+ * check whether BKROGET says that it is read-only. E.g. read-only loop
+ * devices may be openend read-write but are read-only according to BLKROGET
+ */
+ if (readonly == 0) {
+ if (ioctl(fd, BLKROGET, &readonly) < 0) {
+ set_error("BLKROGET failed on device: %s",
+ strerror_r(errno, buf, 128));
+ return -1;
+ }
}
#else
-# error BLKROGET not available
+#error BLKROGET not available
#endif
#ifdef BLKGETSIZE64
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