[PATCH] fix verify_command to allow burning more than 1 DVD

[Michal Schmidt]

Hello,

I use K3B with growisofs to burn DVDs. After boot I can burn a DVD as a 
normal user. But only the first one. When I want to burn another one, 
K3B complains that it is unable to prevent media removal. Then only root 
can burn DVDs.
The bug is in the kernel in the function verify_command.
When a process opens the DVD recorder with O_RDONLY and issues a command 
which is marked safe_for_write, this function is supposed to just return 
-EPERM and do nothing more. However, there is a bug that causes the 
command to be marked as CMD_WARNED. From now on no non-privileged 
process is able to issue this command even if it correctly opens the 
device with O_RDWR - because the command is no longer marked as 
CMD_WRITE_SAFE.
A patch is attached.

Michal
--- linux-2.6.11-mm1/drivers/block/scsi_ioctl.c.orig	2005-01-17 20:42:40.000000000 +0100
+++ linux-2.6.11-mm1/drivers/block/scsi_ioctl.c	2005-01-17 20:43:14.000000000 +0100
@@ -197,9 +197,7 @@ static int verify_command(struct file *f
 	if (type & CMD_WRITE_SAFE) {
 		if (file->f_mode & FMODE_WRITE)
 			return 0;
-	}
-
-	if (!(type & CMD_WARNED)) {
+	} else if (!(type & CMD_WARNED)) {
 		cmd_type[cmd[0]] = CMD_WARNED;
 		printk(KERN_WARNING "scsi: unknown opcode 0x%02x\n", cmd[0]);
 	}