PATCH: open()ing non-existant partitions on IDE devices, 2.3.35

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Hello,

While coding up a utility for myself that uses the IDE ioctls() to get
information that would be much easier to get from /proc, I stumbled on what
appears to be a bug in the ide driver's open code (ide_open()).

I noticed that it appears perfectly legal to open() a partition (/dev/hda4, for
instance) when no such partition actually exists. You can't actually write to it
(it's a zero-byte read-only file, it seems) but you can open it.

According to the manpage for open():

ENXIO
          O_NONBLOCK | O_WRONLY is set, the named file is a FIFO and no process
has the file open for reading. Or, the file is a device special file and no
          corresponding device exists.

Unless I misunderstand, we should be returning ENXIO as there is no device that
cooresponds to that node. (Admittably, this is a gray area. The
device exists (/dev/hda) but there is no partition at that location.) The
problem is that ide_open only checks to see if the major number is a valid
device,
and no check is performed at that level to see if there is a matching partition
(minor number). I correct this by looking in the partition table and checking to
 see
 if the number of sectors in the selected partition is zero, in which case I
assume that there is no matching partition in the table. (This is a bug in my
patch, it is
possible in many partition systems to have a zero byte partition, it just isn't
very useful.)

(See attached file: ide.patch)

I have attached the patch, please let me know if this is valid or if I am
misunderstanding the situation. The patch is against 2.3.35.

Joe

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